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The effect of feeding frequency on the respiratory metabolism of sablefish (Anoplopoma fimbria) Furnell, Donald James 1987

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THE EFFECT OF FEEDING FREQUENCY ON THE RESPIRATORY METABOLISM OF SABLEFISH (Anoplopoma f i m b r i a ) By DONALD JAMES FURNELL B . S c , The U n i v e r s i t y o£ V i c t o r i a , (1977) Sc., The U n i v e r s i t y of B r i t i s h Columbia, (1983) A THESIS SUBIMTTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES Department of Zoology We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH A p r i l 1987 Donald James F u r n e l l , COLUMBIA 1987 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6(3/81) ABSTRACT: The three components of the aerobic respiratory metabolism of s a b l e f i s h , digestion (SDA), a c t i v i t y , and standard metabolism, were examined . separately and together as dependent variables responding to the independent variable, feeding frequency. A l l f i s h were sim i l a r in size and held within a temperature range of 8.5 - 9.5 C on a 12 hr photoperiod. Fish were studied in both 4000 L mass respirometers equipped with a c t i v i t y meters and in a tunnel respirometer. Identical meals were given every 4, 7, and 14 days. A fourth series of starved f i s h served as controls. In the mass respirometers, oxygen consumption, ammonia nitrogen excretion, and a c t i v i t y were monitored continuously before, during, and aft e r acclimation to the d i f f e r e n t feeding frequencies. This permitted estimation of t o t a l metabolism, the a c t i v i t y and feeding components of t o t a l metabolism, standard metabolism, and protein and l i p i d catabolism. In the tunnel respirometer, energy expenditures at similar levels of Imposed a c t i v i t y were compared before and after eating to examine re p a r t i t i o n i n g of locomotor and feeding metabolism. It was found that swimming energy expenditures and standard metabolism are a sigmoid functions of rat i o n frequency. The lowest metabolic rates are associated with the least frequent feedings and the greatest with the most frequent meals. Consequently, t o t a l and routine metabolic rates are also d i r e c t functions of rat i o n history. The lowest metabolic rates are based on l i p i d oxidation as an energy source. The f i s h primarily oxidize proteins to meet metabolic needs when on higher rations. It i s also shown that apparent s p e c i f i c dynamic action (SDA) r e s u l t s to a greater extent from catabolic rather than anabolic processes. When the dual metabolic load of locomotion and digestion threatens to exceed the aerobic metabolic scope of the f i s h , a physiological mechanism exists whereby oxygen supply i s p r e f e r e n t i a l l y shunted to locomotor requirements. When spontaneously active in the mass respirometers, the a c t i v i t y component of metabolism is generally less than 25% of the standard metabolic rate and digestion and locomotion can proceed synchronously. When swimming spontaneously, the sa b l e f i s h move at a sing l e , probably optimal v e l o c i t y regardless of ration history. The better fed f i s h in the experiments were active most of the day despite the low contribution of the a c t i v i t y component to the routine metabolic rate. These results have sig n i f i c a n c e regarding assumptions often made in bioenergetic models, s p e c i f i c a l l y that a c t i v i t y energy expenditures and standard metabolic rates are independent of rat i o n . They reveal an adaptable physiology which applies d i f f e r e n t energy p a r t i t i o n i n g strategies to meet the changing metabolic needs of f i s h in a dynamic environment with a variable food supply. TABLE OF CONTENTS: Contents Page Abstract i i L i s t of Tables v i L i s t of Figures... v i i Acknowledgements ix Chapter 1: General Introduction and Methods 1 1.0 Introduction 1 1.1 Feeding Metabolism 5 1.2 A c t i v i t y Metabolism 7 1.3 Standard Metabolic Rate 10 1.4 Summary 11 1.5 The Study Species 12 1.6 General Methods 13 Chapter 2: The E f f e c t of Ration on the Nutrient P a r t i t i o n i n g Strategy and Feeding Metabolism (SDA) of sa b l e f i s h 15 2.0 Introduction 15 2.1 Methods 16 2.2 Results 20 2.3 Discussion 31 Chapter 3: The Ef f e c t of Ration on the A c t i v i t y and Standard Metabolism of Sablefish 39 3.0 Introduction 39 3.1 Methods 41 3.2 Results 45 3.3 Discussion 61 iv Chapter 4: P a r t i t i o n i n g of Locomotor and Feeding Metabolism 66 4.0 Introduction 66 4.1 Methods 67 4.2 Results 70 4.3 Discussion 74 Chapter 5: General Discussion 77 5.0 Summary 86 6.0 Literature Cited 88 v LIST OF TABLES: Table Page 2.1 Energy, protein and l i p i d budgets for sa b l e f i s h with d i f f e r e n t feeding intervals 33 2.2 Estimates of SDA for s a b l e f i s h with d i f f e r e n t feeding intervals 37 3.1 D e f i n i t i o n of pre and post-acclimation feedings 47 3.2 Between meal d a i l y a c t i v i t y for sa b l e f i s h acclimated to d i f f e r e n t feeding intervals 56 v i LIST OF FIGURES: Figure Number T i t l e Page 2.1 Oxygen consumption of sa b l e f i s h acclimated to d i f f e r e n t feeding intervals 21 2.2 Oxygen consumption and ammonia nitrogen excretion of sab l e f i s h during acclimation to weekly meals 22 2.3 Oxygen consumption and ammonia nitrogen excretion of sab l e f i s h during acclimation to meals every 4 days....23 2.4 Ammonia nitrogen excretion of s a b l e f i s h acclimated to d i f f e r e n t feeding intervals 25 2.5 Total and protien dependent energy expenditures of sab l e f i s h during starvation 27 2.6 Total and protein dependent energy expenditures of sab l e f i s h after acclimation to meals every 14 days....28 2.7 Total and protein dependent energy expenditures of sab l e f i s h a f t e r acclimation to meals every 7 days 29 2.8 Total and protein dependent energy expenditures of sa b l e f i s h a f t e r acclimation to meals every 4 days 30 3.1 The a c t i v i t y meter 43 3.2 Daily a c t i v i t y counts for s a b l e f i s h acclimated to d i f f e r e n t feeding intervals 46 3.3 Total metabolism of sa b l e f i s h acclimated to d i f f e r e n t feeding intervals 49 3.4 Regressions of oxygen consumptln and a c t i v i t y counts for s a b l e f i s h acclimated to meals every 4 days 50 3.5 Regressions of oxygen consumption and a c t i v i t y counts for s a b l e f i s h acclimated to meals every 7 days 51 3.6 Regressions of oxygen consumption and a c t i v i t y counts for s a b l e f i s h acclimated to meals every 14 days 52 3.7 Standard and digestive metabolism of sa b l e f i s h acclimated to d i f f e r e n t feeding inte r v a l s 54 3.8 A c t i v i t y metabolism of s a b l e f i s h acclimated to d i f f e r e n t feeding intervals 55 3.9 Relationship between a c t i v i t y metabolism and ratio n in sa b l e f i s h acclimated to d i f f e r e n t feeding i n t e r v a l s . . . 57 vi i 3.10 Relationship between standard metabolism and rati o n in sa b l e f i s h acclimated to d i f f e r e n t feeding intervals 59 3.11 Relationship between routine metabolism and rati o n in sa b l e f i s h acclimated to d i f f e r e n t feeding intervals 60 4.1 Oxygen consumption of s a b l e f i s h in a 4000 L mass respirometer after acclimation to weekly meals 71 4.2 Oxygen consumption of s a b l e f i s h in a tunnel respirometer before and after feeding 73 v i i i ACKNOWLEDGEMENTS: Many individuals in several organizations contributed to th i s research and the i r assistance is g r e a t f u l l y acknowledged. The B r i t i s h Columbia Science Council provided personal support with a Graduate Research in Engineering and Technology Award. The Natural Sciences and Engineering Research Council of Canada provided an NSERC Post-graduate Scholarship. A l l research expenses and equipment were supplied by the Canadian Department of Fisheries and Oceans, P a c i f i c B i o l o g i c a l Station. Academic and moral support was given f r e e l y by Dr. J.R. Brett. His insights and enthusiasm were invaluable. Drs. D.J. Randall and A.V. Tyler provided c r i t i c a l appraisal of manuscripts and administrative support. Much of t h i s work was conducted at the P a c i f i c B i o l o g i c a l Station in Nanaimo, B.C. and the s t a f f was of great assistance, s p e c i f i c a l l y , G.A. McFarlane, Dr. Ian White, Dr. C.C. Wood, Dr. C. Clarke, J. Blackburn, J. Shelbourn, H. Kreiberg, W. Shaw, and M. Smith. The remaining research was perfomed at the Bamfield Marine Station with assistance from Dr. R. Foreman and J . Glazier. For t h e i r patience and perserverence in the face of long and inconvenient hours, I also g r e a t f u l l y acknowledge my wife Susan and daughter Rebecca. ix CHAPTER 1: GENERAL INTRODUCTION AND METHODS 1.0 INTRODUCTION: Studies of energy flow through an organism are refered to as bioenergetics (Beamish et a l . 1975) or physiological energetics (Brett and Groves 1979). Rubner (1894, 1902) pioneered such work in homeotherms, the history of which is extensively reviewed by Brody (1945) and Kleiber (1975). The foundation of f i s h bioenergetics can be attributed to Ivlev (1939, 1945), although e a r l i e r publications on the topic appear (Ege and Krogh 1914, Dawes 1930, Pentlow 1939). Energetics research gained importance as f i s h culture developed and a th e o r e t i c a l background for understanding the relationships between feeding and growth became necessary. Concurrently, bioenergetics research contributed to the management of wild f i s h stocks (Paloheimo and Dickie 1966a, 1966b, Kelso 1972, K i t c h e l l and Stewart 1977, Ware 1980, Kerr 1971a, b, c, 1982). These contributions provide a means of studying i n t e r s p e c i f i c e f f e c t s of f i s h i n g and enable managers to adopt multi-species, rather than the more t r a d i t i o n a l single species models. The d i f f i c u l t y in using bioenergetics for fish e r y management l i e s in tr a n s f e r r i n g laboratory estimates of metabolic parameters to f i s h in nature, e s p e c i a l l y understanding how a c t i v i t y i s regulated and i t s importance in energy flow. This research addresses the regulatory role that r a t i o n may play over aspects of the three generally recognized components of respiratory metabolism: 1) a c t i v i t y , 2) digestion, and 3) standard or maintenance metabolism. Consideration i s also given to the interaction of the variables digestion and a c t i v i t y , and 1 the energy sources used to power metabolism. The t h e o r e t i c a l framework upon which bioenergetic models are b u i l t i s the balanced energy equation, in a more or less complex form depending on a n l y t i c a l objectives (Ivlev 1945, Winberg 1956, Warren and Davis 1967, Weatherly 1972, Webb 1978, Brett and Groves 1979, Calow 1985). It serves as an accounting of a l l energy inputs and expenditures experienced by an organism, these being equated by the f i r s t law of thermodynamics and the law of constant heats (Kleiber 1975). The equation's variables usually have units of energy/time, although they can be expressed on a meal to meal basis. The symbols and d e f i n i t i o n s below follow the International B i o l o g i c a l Program standard as presented by Davis and Warren (1968). C = F + U + dB + Rs + Rd + Ra (1) Where: C = Energy value of the food consumed F = Energy value of faeces U = Energy value of materials excreted in the urine or through the g i l l s and skin dB = Total change in energy value of body materials (growth) including both somatic and reproductive tissues Rs = Energy released by the metabolism of unfed, resting f i s h (standard metabolism) Rd = Energy released during consumption, digestion, a s s i m i l a t i o n , storage, and catabolism of materials consumed Ra = Energy released in swimming and other a c t i v i t y 2 Because metabolism varies with s i z e , the parameters are generally expressed r e l a t i v e to weight r e s u l t i n g in units of energy/weight/time. In heterotherms, s p e c i f i c a l l y fishes, the time scale of the r e l a t i o n s h i p can be altered by a b i o t i c c o n t r o l l i n g factors (Fry 1947, 1971, Brett 1979) such as temperature. Body size and temperature are the two most important variables, e x t r i n s i c to the equation, influencing the re l a t i o n s h i p . This has been demonstrated by multiple regression anlysis (Wohlschlag 1960, Stauffer 1973, E l l i o t t 1976a) and implies that any experimental investigation must be designed to include or control for variations in body size and temperature. Within the equation, ration i s a l i m i t i n g factor representing the input of environmental energy to the organism. Most f i s h can l i v e , grow and reproduce over a wide range of ration l e v e l s , however, the proportions and magnitudes of r i g h t -hand variables in the equation depend on ration (Priede 1985). The most extensively studied interaction of ration with r i g h t -hand variables concerns growth rates and conversion e f f i c i e n c i e s . Paloheimo and Dickie (1965) used the energy equation in more general form. pR = T + dW / dt (2) Where: R = Ration p = Proportion of rat i o n assimilated; equivalent to 1-((F+U)/C) (eq. 1) T = Total metabolism; equivalent to Rd+Rs+Ra (eq.l) dW = Change in weight or c a l o r i e s (dB in eq. 1) dt = Change in time 3 They express conversion e f f i c i e n c y as Ivlev's (1945) f i r s t order term ( K l ) . -a -bR Kl = dW / Rdt = e (3) Where: a and b are constants Reviewing f i s h growth l i t e r a t u r e , these authors conclude that conversion e f f i c i e n c y i s a decreasing function of r a t i o n , having linear form on a logarithmic plot as indicated by the negative slope of the far right hand term in the expression. The negative slope r e s u l t s from an increase in the metabolic term (T) of the s i m p l i f i e d energy equation (eq. 2) which they equate to the widely accepted weight-power function for standard metabolism (Fry 1947, 1971). b T = aW (4) Where: a = C o e f f i c i e n t or l e v e l of metabolism b = Weight exponent of metabolism They conclude that the exponent, b, i s r e l a t i v e l y constant over a l l ranges of weight, r a t i o n , and l e v e l of metabolic a c t i v i t y and that changes in the c o e f f i c i e n t , a, account for the logarithmic decrease in Kl with increased r a t i o n . They do not, however, speculate on the form of the r e l a t i o n s h i p between 'a' and ration because they lack data. In general terms, the r e l a t i o n s h i p proposed by Paloheimo and Dickie may be true (Labrasseur 1969, Kerr 1971a, 1971b, 1982) and in many species a decrease in Kl has been observed at high ration l e v e l s . This is attributed to elevated t o t a l metabolism (T, equation 4) which i s equivalent to the sum of Rs, Rd, and Ra in equation 1. It i s therefore of both t h e o r e t i c a l and p r a c t i c a l 4 Interest to understand the r e l a t i o n s h i p between the three metabolic subcomponents and the l e v e l of ration intake. Further, because the l e v e l of t o t a l aerobic metabolism i s limited by the rate of oxygen uptake (Jones 1971, Brett and Groves 1979) i t i s important to observe how these subcomponents interact both under normal conditions and when they threaten to exceed the aerobic metabolic scope. 1.1 FEEDING METABOLISM, Rd: Feeding metabolism, as used in t h i s presentation, encompasses the energy expended capturing, absorbing, assimilating and catabolizing food exclusive of concurrent energy expenditures on swimming and standard metabolism. Beamish (1974) termed t h i s the apparent s p e c i f i c dynamic action (SDA). In f i s h , t h i s i s observed as an elevation of energy expenditure, measured as increased oxygen consumption, coincident with feeding and continuing for a s i g n i f i c a n t period afterward. The magnitude and duration of the e f f e c t appears to be a d i r e c t function of ration q u a l i t y and quantity, in s i m i l a r l y acclimated f i s h . The i n i t i a l r i s e in metabolic rate, immediately after eating, i s due to excitment and the mechanical energy expended obtaining and ingesting food. Tandler and Beamish (1979) have documented these expenditures separately and found the mechanical costs to be of l i t t l e s i g n i f i c a n c e compared with the overa l l feeding expenditures. By giving f i s h i s o - c a l o r i c diets of d i f f e r e n t volume, estimates can also be made of the energy expenditure made on gut mechanics which are again not thought to be s i g n i f i c a n t . The cost of enzyme manufacture, digestion, and absorption of food 5 from the gut into c i r c u l a t i o n i s not well known nor has i t been separated from the costs of c e l l u l a r metabolite c a t a l y s i s or the costs of retaining metabolites as t i s s u e . Controversy exists regarding the sources of SDA subsequent to absorption, s p e c i f i c a l l y whether i t i s due to catabolic or anabolic processes or both. T r a d i t i o n a l l y , SDA was thought to originate primarily from deamination of amino acids in the l i v e r with lesser contributions from carbohydrate and l i p i d catabolism (Beamish 1974, Kleiber 1975, Brett and Groves 1979). More recently, some authors have associated SDA with the anabolic deposition of tissue (Jobling 1981, 1983, 1985). These are fundamental and seemingly i r r e c o n c i l a b l e differences in the way feeding metabolism i s viewed. The contention comes from the observation that conditions which support maximum growth also display the maximum SDA. Unfortunately, the conditions which support maximum growth are also those in which the greatest amount of food i s being consumed. Thus i t i s d i f f i c u l t to decouple growth and catabolism to i d e n t i f y one or the other as the primary cause of SDA. If one views f i s h as dynamic chemical systems attempting to maintain homeostasis despite a variable supply of ration from the environment, the question arises of how the current physiological state a f f e c t s the strategy of metabolite ( i . e . energy) u t i l i z a t i o n . It is important to consider the feeding state or recent r a t i o n history of a f i s h on the fate of absorbed nutrients. A f i s h deprived of nutrients may require a d i f f e r e n t p a r t i t i o n i n g of anabolic and catabolic processes to maintain s t r u c t u r a l i n t e g r i t y compared to a well fed f i s h . The 6 controversy surrounding the cause of apparent SDA or feeding metabolism may be approached using t h i s perspective. By comparing the metabolic response as well as the l e v e l of protein catabolism ( i . e . nitrogen excretion) shown by f i s h given i d e n t i c a l meals after experiencing d i f f e r e n t ration h i s t o r i e s in which p a r t i t i o n i n g of anabolism and catabolism may be d i f f e r e n t , some understanding of the cause of SDA may be possible. 1.2 ACTIVITY METABOLISM, Ra: The term a c t i v i t y metabolism, as used in t h i s presentation, w i l l refer to the energy a f i s h expends swimming exclusive of concurrent standard metabolism and possible SDA. The metabolic components, Rs and Ra, in r e l a t i o n to ra t i o n , exclusive of the energetic costs of food digestion, have only been dealt with hypothetically for f i s h (Kerr 1971b, c, 1982) with components estimated by difference from published growth data. Although estimating energy equation variables by difference leads to compounding of errors in the remainders (Solomon and B r a f i e l d 1972), Kerr's r e s u l t s suggest that foraging a c t i v i t y may be a function of r a t i o n . This raises the question of whether ration differences cause a c t i v i t y differences and i f so what the form and magnitude of the r e l a t i o n s h i p i s . Active swimming while foraging is probably the most important energy expenditure of predatory fishes, e s p e c i a l l y pelagic species (Kerr 1982). Other a c t i v i t i e s such as reproductive behavior, t e r r i t o r y defense, s o c i a l interaction, or escape from predation also contribute to the active metabolic l e v e l , e s p e c i a l l y in sedentary t e r r i t o r i a l f ishes. However, for 7 pelagic, predatory species, t h e i r magnitude, in the long term, i s not of great s i g n i f i c a n c e (Schoener 1971, Pyke et a l . 1977, Kerr 1982). A change in a c t i v i t y has two components; i n t e n s i t y and duration. A f i s h may maintain a constant swimming speed and be active over d i f f e r e n t periods, i t can a l t e r swimming speed and re t a i n constant periods of a c t i v i t y , or i t can do both. Ware (1975, 1978) discusses the s e l e c t i v e advantages of swimming at d i f f e r e n t speeds and suggests there are two swimming speeds which may be s e l e c t i v e l y optimized, c r u i s i n g speed and foraging speed. For each unit of energy spent, the former gives the greatest distance, the l a t t e r the greatest c a l o r i c return, at a given prey density. Although conceptually d i s t i n c t , i t is d i f f i c u l t to apply these d i s t i n c t i o n s to naturally occurring fishes. Fish search for prey when hungry; hence, foraging speed could apply to f i s h t r a v e l l i n g long distances or c r u i s i n g while seeking contagiously d i s t r i b u t e d prey. Optimal foraging speed i s thought to increase asymptotically with prey density (Ware 1975, 1978) in a t y p i c a l functional response (Holling 1959). Further evidence that foraging speed changes in response to prey density is found in the A t l a n t i c mackerel (Muir and Newcombe 1974) and anchovy larvae (Hunter and Thomas 1974). This suggests that i t may be a change in the i n t e n s i t y component of foraging rather than duration which causes the increase in the a c t i v i t y component of metabolism at higher ration l e v e l s . These observations are, however, for uniformly d i s t r i b u t e d prey. It i s possible that a predator in an environment with contagiously d i s t r i b u t e d , motile prey would do 8 well to increase the time spent searching had i t recently eaten, and prey were in i t s v i c i n i t y , and reduce search time following starvation. By increasing search time when prey were abundant and reducing i t when prey were scarce, a predator might operate more e f f i c i e n t l y than by making equal expenditures regardless of prey density. Evidence of t h i s comes from observations of reduced a c t i v i t y during starvation (Brown 1946a, Magnuson 1962, Beamish 1964a, Belkin 1965, Glass 1968). Recent ration history or ration acclimatization may serve as a cueing mechanism to optimize foraging a c t i v i t y energy expenditures. From the foregoing discussion, i t i s apparent that foraging a c t i v i t y can be divided into two areas: 1) energy spent capturing and eating prey, and 2) energy spent post-feeding when searching for prey, both of which may be related to immediate and long term ration history. The extent to which ration related changes in a c t i v i t y contribute to the l e v e l of t o t a l metabolism ('a1, eq. 4) is unknown. They may account for the decline in conversion e f f i c i e n c y at high rat i o n l e v e l s , observed by Paloheimo and Dickie (1966a), and provide f i s h with a means of optimally responding to changes in prey density and d i s t r i b u t i o n . The only data currently available to examine t h i s p o s s i b i l i t y have been colle c t e d for other purposes. Consequently, they are without proper controls and require application of uncertain assumptions with no kowledge of r e s u l t i n g error magnitudes (Paloheimo and Dickie 1966a). The present research examines the e f f e c t of ration levels on a c t i v i t y and t h e i r combined e f f e c t on the level of t o t a l metabolism. This should provide information on the energy devoted both to searching for and consuming prey and 9 e s t a b l i s h i f these expenditures are related to either long term or immediate rati o n history. 1.3 STANDARD METABOLIC RATE, Rs: Standard metabolism i s defined as the energy expenditure of a r e s t i n g , post-absorptive f i s h at a s p e c i f i e d temperature. It is assumed to be constant in any feeding state, although only measured in post-absorptive f i s h . The standard rate is constituted in part by c i r c u l a t o r y and respiratory mechanics, but also includes the sum of a l l endothermic enzyme reactions not associated with feeding or locomotion. This leads to d i f f i c u l t y predicting the standard rate under d i f f e r e n t conditions. For example, i s the cost of acetylcholine and acetylcholine esterase synthesis a locomotor cost of the nervous work done in muscle contraction or i s i t part of the standard metabolic rate associated with neural functioning? Many reaction rates depend, in part, on substrate concentration. Immediate and long term ration history may influence the concentration of routinely c i r c u l a t i n g metabolites such as amino acids and hence, may a f f e c t the standard metabolic rate. Much of the problem l i e s in the d e f i n i t i o n of standard metabolic rate. Rather than describing s p e c i f i c energy-consuming functions the contemporary d e f i n i t i o n has comparative value, but limited predictive value. R e l a t i v e l y l i t t l e work has been done on the effects ration history has on the standard metabolic rate of fishes because measurements of metabolism are usually not made synchronously with a c t i v i t y monitoring. It i s therefore d i f f i c u l t to eliminate a c t i v i t y metabolism from t o t a l metabolism to estimate Rs. 10 Further, standard metabolic rate, as normally defined, assumes th i s component of t o t a l energy expenditure i s constant, regardless of the fishes' condition and therefore requires no examination beyond documentation at the defined l e v e l . Beamish (1964a) reports a decrease in the standard metabolic rate of white suckers (Catastomus commezsonii) and brook trout (Salvelinus f o n t i n a l i s ) with starvation over two days. There is no work dealing with a dose-response curve between rati o n and standard metabolic rate, although given the enzymatic consideration discussed above such a rel a t i o n s h i p would not be su r p r i s i n g . This would have an impact on energetics modeling of f i s h populations where the standard metabolic rate is generally considered dependent only on temperature and body mass. This research w i l l therefore examine the response of the standard metabolic rate, as normally defined and measured, to d i f f e r e n t levels of food consumption and the proportion of t o t a l metabolism i t represents. 1.4 SUMMARY: The following presentation examines the impact ration has upon the three recognized components of respiratory metabolism, Rs, Rd, and Ra. This w i l l provide insights into the energy p a r t i t i o n i n g strategies s a b l e f i s h use when interacting with their environment and i t s variable food supply. S p e c i f i c hypotheses are: 1) A c t i v i t y metabolism i s independent of ration history. 2) Standard metabolism, as currently defined, i s independent of ration history. 11 3) Feeding metabolism, r e s u l t i n g from i d e n t i c a l meals, i s independent of ration history. 4) Feeding metabolism is a result of both anabolic and catabolic processes which can be separated. 5) Changing metabolic demands can r e p a r t i t i o n energy supply among the respiratory metabolic components. These questions w i l l be addressed in separate chapters written as independent studies with a preceding general methods section and discussed as a whole in a f i n a l general discussion. 1.5 THE STUDY SPECIES: The s a b l e f i s h or blackcod, Anoplopoma fimbria Pallas (Hart 1973), was chosen for experiments. It is a bathypelagic f i s h found off the north eastern P a c i f i c coast. Adults occur most abundantly near 700m depth. Lacking a swim bladder, the sab l e f i s h i s e a s i l y taken a l i v e in good condition from great depth. Because i t i s a species of considerable commercial importance with excellent potential for domestication (Kennedy and Fletcher 1968, Kennedy 1969, 1970, 1971), sa b l e f i s h are intensively managed. Advantages of t h i s species as a research subject include 1) hardiness in the laboratory (Sullivan 1982, Sullivan and Smith 1982), 2) the large range of sizes available (Beamish and Chilton 1982), 3) i t s habit of slow steady swimming amenable to tunnel respirometry with low variance results (Brett pers. comm.), 4) resistance to disturbances, 5) tolerance of low oxygen concentrations t y p i c a l of bathypelagic species (Blaxter 1979), and 6) ready acceptance of a great v a r i e t y of foods while in c a p t i v i t y . A l l f i s h used in t h i s study were approximately one 12 kg in weight and sexually immature. This size was selected based on i t s a v a i l a b i l i t y and s u i t a b i l i t y to the experimental equipment. A l l s a b l e f i s h used were held in c a p t i v i t y for at least s i x months prior to experiments and acclimated to a 12 hr photoperiod at 8° - 9° C. They were fed 50 g of chopped herring per f i s h weekly with occasional 50 g meals of squid in place of herr ing. 1.6 GENERAL METHODS: Estimating energy equation variables requires calorimetric analysis. These experiments employed two types of in d i r e c t calorimetry to measure metabolic energy and d i r e c t oxidative calorimetry to estimate the energy of food given to s a b l e f i s h during the experiments. Indirect calorimeters monitor the oxygen consumption of an organism, which can be converted to the energy released by applying o x y c a l o r i f i c equivalents (Brett and Groves 1979, Brett 1985). The primary indir e c t c alorimetric method used was mass respirometry. This continuously measures the oxygen consumption of groups of f i s h l i v i n g in large containers while isolated from atmospheric oxygen (Saunders 1963, Solomom and B r a f i e l d 1972, Pierce and Wissing 1974). The calculated energy release from such a system i s the sum of standard, a c t i v i t y , and digestive metabolism. Each mass respirometer was also equipped with two mechano-electric a c t i v i t y meters to record f i s h a c t i v i t y synchronously with respiratory measurements. Two mass respirometers were used with groups of 5 uniform size f i s h having approximately 5 kg t o t a l biomass acclimated to four ration 13 l e v e l s . Details of respirometer operation are provided in the methods sections of the following chapters. The mass respirometers consisted of large oval (4 X 2.7 X 1.5 m deep and 4000 L volume) fiberglass tanks f i t t e d with translucent, f l o a t i n g PVC blankets which extended over the entire water surface and excluded atmospheric oxygen. The blankets were constructed from p l a s t i c bubbles (5mm diameter) sandwiched between two 0.4 mm sheets of PVC. When the respirometers were in use, heat exchangers with c i r c u l a t i n g pumps (800 L/hr) mixed the water and maintained a temperature of 8.5°+0.5°C. The e f f i c a c y of the blankets to exclude atmospheric oxygen was examined by f i l l i n g the tanks with oxygen-stripped sea water (nitrogen purged to an oxygen concentration of 2.0 mg/L) and allowing the respirometer to operate. No detectable change was observed in oxygen concentration over a five-day period; f i s h experiments were conducted over only 24 hours. Further, control tests were made for b a c t e r i a l oxidation with no f i s h in the tanks, both before and after individual experiments, using oxygen saturated sea water. Again there was no detectable change in oxygen concentration over 24 hours. A l l oxygen analysis was by the azide modified Winkler t i t r a t i o n method (Strickland and Parsons 1972); duplicate t i t r a t i o n s of two samples (n=4) constituted each determination with an a n a l y t i c a l precision of +.0.02 mg/L (95% confidence i n t e r v a l ) . 14 CHAPTER 2: THE EFFECT OF RATION ON THE NUTRIENT PARTITIONING STRATEGY AND FEEDING METABOLISM (SDA) OF SABLEFISH 2.0 INTRODUCTION: The terms s p e c i f i c dynamic action (SDA), apparent SDA, heat increment, feeding metabolism and dietary induced thermogenesis, among others, have a l l been used to describe the elevation of energy expenditure associated with ingestion of food in animals (Brody 1945, Beamish 1974, Kleiber 1975, Brett and Groves 1979, Jobling 1981). In t h i s presentation these terms w i l l be taken to mean Rd as presented in equation 1 (chapter 1), hence only the actual elevation of energy expenditure, exclusive of the concurrent standard (Rs) and a c t i v i t y (Ra) costs i s considered here. The controversy surrounding the cause of SDA has been presented; some consider SDA to r e s u l t from catabolic processes, others from anabolism or both. Generally, studies have examined SDA using fishes acclimated to reg u l a r l y fed meals of d i f f e r e n t s i z e s . The re s u l t i n g measurements of digestive metabolic processes are s t r i k i n g l y consistent. Energy costs are usually found to be a function of the quantity and composition of the meal (Muir and Niimi 1972, Beamish 1974, Brett 1976, Tandler and Beamish 1979, Vahl and Davenport 1979). Unfortunately, the ratio n of free l i v i n g fishes does not match that of laboratory specimens in either q u a l i t y or re g u l a r i t y . Given the variable supply of energy available to wild fishes i t would seem reasonable to suspect that d i f f e r e n t 15 physiological pathways would be used to assign metabolites to processes, either catabolic or anabolic, f u l f i l l i n g the greatest metabolic need. Differences in the dietary history of laboratory specimens, r e s u l t i n g in d i f f e r e n t metabolite processing pathways may, in part, underlie the controversy in the l i t e r a t u r e on feeding metabolism. This study was i n i t i a t e d to examine the p o s s i b i l i t y that with d i f f e r e n t feeding frequencies the s a b l e f i s h might respond d i f f e r e n t l y to meals of similar size and q u a l i t y . In the experiments the t o t a l metabolic energy expenditure (as measured by oxygen consumption) and energy expenditure due to protein catabolism (as measured by ammonia nitrogen excretion) was followed before, during, and after acclimation to d i f f e r e n t feeding i n t e r v a l s . In t h i s manner, i t was hoped to gain insights into the species' catabolic and anabolic strategies given d i f f e r e n t feeding opportunities. 2.1 METHODS: The metabolic expenditures of s a b l e f i s h were examined using groups of 5 individuals maintained in the mass respirometers. A l l f i s h were approximately one kg in wet body weight (X=1.125 +_ 0.164 kg S.D., n=50), sexually immature, healthy, and had been held in c a p t i v i t y for at least 6 months prior to experiments. Before and during experiments, photoperiods were normally kept at 12 hr and water temperatures at 8.5°+ 0.5° C. During holding, f i s h were fed chopped herring and squid, prey commonly found in s a b l e f i s h stomachs (McFarlane and Beamish 1983); during experiments, however, only herring was fed. A l l meals were 16 approximately 5% o£ the fishes' wet body weight ( i . e . 50 g) with feeding frequency altered to simulate d i f f e r e n t feeding opportunities. The meals were below the maximum single meal size which varied in proportion to the preceding starvation time as i s commonly observed (Pandian 1967a, Tyler and Dunn 1976). These submaximum meals were given because a l l f i s h fed aggressively at th i s l e v e l r e s u l t i n g in an equal d i s t r i b u t i o n of food among the five individuals in each respirometer. With larger meals some individuals tended to become sated more quickly, while others continued feeding, r e s u l t i n g in an unequal d i s t r i b u t i o n of the food. Meals were given weekly during holding and the f i s h were starved for 3 weeks (500 hr) before an experiment began. The starvation period enabled observations to be made while the f i s h were acclimating to the d i f f e r e n t r a t i o n treatments and was necessary because one treatment was the same as the holding feeding frequency of the experimental stock. To eliminate the potential for metabolic compensation ( i . e . reduced oxygen consumption) at low oxygen levels (Sullivan and Smith 1982), the biomass in each respirometer was selected to l i m i t oxygen depletion to not more than 75% of the inflow water's air-saturated concentration. During an oxygen consumption determination, water flow to the tanks was c u r t a i l e d for 24 hours and consumption estimates based on the oxygen concentration difference between the average of two i n i t i a l and two f i n a l water samples. Heat exchangers with submersible water pumps circulated the water, preventing s t r a t i f i c a t i o n , and maintained water temperatures. The 24-hour determination period was selected because s a b l e f i s h are d i u r n a l l y active and for comparative purposes It was necessary to keep a c t i v i t y metabolism as constant as possible between determinations. During the same period, i n i t i a l and f i n a l water samples were taken for ammonia analysis by the indophenol method (Strickland and Parsons 1972) calibrated to ammonium chloride standards over the range of expected values. To minimize contamination, sample and analysis bottles were acid washed, rinsed with copious amounts of deionized water, then flushed twice with sample water before use. Tests of the mass respirometers for possible ammonia contamination or b a c t e r i a l oxidation were made, without f i s h in the tanks, by comparing ammonia concentrations of respirometer water samples taken 24 hr apart at the beginning and end of each experimental s e r i e s . No s i g n i f i c a n t difference was found between i n i t i a l and f i n a l ammonia concentrations regardless of the i n i t i a l concentration. The low surface to volume rel a t i o n s of such large respirometers and low experimental temperatures l i k e l y contributed to minimizing these potential biases. Further, during the f i r s t experiments, 24 hour differences in urea nitrogen concentration were monitored by the urease method (Strickland and Parsons 1972), but were found to be below the l i m i t s of detection even in starving f i s h which tend to excrete more urea ( E l l i o t t 1979); consequently such sampling was discontinued after 50 days. The herring used as experimental food was obtained in two lots from a single supplier and maintained frozen at -30 C. Over the experimental period, the proximate composition and c a l o r i c content of the herring was determined reqularly to check consistency and permit estimation of nutrient budgets. Water 18 content and c a l o r i c values were determined by l y o p h i l i z a t i o n and the wet oxidation method respectively using the l y o p h i l i z e d whole f i s h homogenates for acid digestion (Maciolek 1962, Craig et a l . 1978, Mackereth et a l . 1978). Estimates of l i p i d content were made following Bligh and Dyer (1959) using a methanol, chloroform, water extraction and separation of whole f i s h homogenate. After l i p i d extraction, the s o l i d residue was dried at 95 C for 48 hr and weighed. The dried residue was then ashed at 500 C for 24 hr and the ash weighed. The weight difference between the dried residue and i t s ash content was considered an estimate of the food's crude protein content. This approach i s j u s t i f i e d by the i n s i g n i f i c a n t carbohydrate content of f i s h tissue (Craig et a l . 1978) and was checked by comparing proximate c a l o r i c values (protein = 5.66 kcal/g, l i p i d = 9.45 kcal/g, Brett and Groves 1979) to those from wet oxidation. Both were in agreement after correcting for the d i f f e r e n t nitrogenous end-products (molecular nitrogen for proximate values and ammonia for acid digestion). Energy expenditure and nitrogen excretion were examined in four ration treatments: 1) starvation, 2) 50 g chopped herring per f i s h fed every 4 days, 3) every 7 days, and 4) every 14 days (this is approximately equivalent to rations of : 1) 0% of wet body weight/day, 2) 1.25%/day, 3) 0.71%/day, and 4) 0.36%/day). Oxygen consumption and nitrogen excretion analysis began with the f i r s t meal (or only meal for starved fish) following an i n i t i a l 3 week (500 hr) f a s t . Results were tabulated d a i l y and after acclimation had been reached, as indicated by a consistent SDA pattern, were continued for a further 5 to 7 feedings. 19 2.2 RESULTS: Oxygen consumption rates (Fig 2.1), after ration acclimation, show that two d i s t i n c t patterns appeared in the data. Starved f i s h and f i s h acclimated to food once every 14 days had an i n i t i a l increase in oxygen consumption rate, due to SDA , of about 15 mg/kg/hr; t h i s response subsided after 7 days and reached a constant or routine l e v e l of about 45 mg/kg/hr. Conversely, the f i s h acclimated to feedings every four or seven days experienced a 30 mg/kg/hr increase in oxygen consumption which returned to a constant routine rate of 60 mg/kg/hr after only 4 days, although t h i s routine rate could only be confirmed in the weekly fed f i s h where a steady state was reached after 4 days (Fig. 2.1). Maximum oxygen consumption occurred in the f i r s t 24 hr both before and after ration acclimation. However, the maximum for f i s h acclimated to meals every 4 and 7 days was approximately 50% greater than for the same f i s h following i n i t i a l starvation and those acclimated to meals every 14 days. Total SDA, referred to l a t e r , is the area under the oxygen consumption curve above the routine oxygen consumption rate (Fig. 2.1) and represented the energy expended on food processing exclusive of standard and a c t i v i t y metabolism. Oxygen consumption rates during the acclimation period (Fig. 2.2A and 2.3A, feedings 2, 3, and 4) showed SDA patterns which were intermediate in magnitude to the starved and acclimated condition. The high v a r i a b i l i t y of these means resulted from the gradual t r a n s i t i o n between feeding states. Changes, re s u l t i n g 20 1 2 3 U 5 6 7 8 9 10 11 12 13 14 Days Post-prandial Figure 2.1. Oxygen consumption of sa b l e f i s h acclimated to di f f e r e n t feeding intervals (4, 7, 14 days and starved). V e r t i c a l l i n e s through each mean equal one S.D. and sample sizes correspond to those in Figs. 2.5-2.8. 21 Figure 2.2. Oxygen consumption (A) and ammonia nitrogen excretion (B) of sa b l e f i s h before (dots: feeding 1), during ( t r i a n g l e s : feedings 2-4), and afte r (squares: feedings 5-9) acclimation to weekly meals. V e r t i c a l l i n e s equal one S.D. and numbers correspond to sample sizes and are the same in A and B. 22 1 2 3 4 1 2 3 4 Days Post-prandial Figure 2.3. Oxygen consumption (A) and ammonia nitrogen excretion (B) of s a b l e f i s h before (dots: feeding 1), during (t r i a n g l e s : feedings 2-4), and aft e r (squares: feedings 5-9) acclimation to meals every 4 days. V e r t i c a l l i n e s equal one S.D. and numbers correspond to sample sizes and are the same in A and B. 23 from acclimation, can only be I l l u s t r a t e d for the 4 and 7-day ration treatments as the 14-day treatment showed no difference with the starved condition (Fig. 2.1). During acclimation of the f i s h fed every 7 days (Fig. 2.2A) there was also a change in the time before a constant routine rate was reached. After acclimation, oxygen consumption became constant after 4 days; however, in fasted and acclimating f i s h the rate continued to decrease over a week-long period (Fig. 2.2A). Ammonia excretion rates were highly correlated with oxygen 2 consumption rates (r =0.94, n=289), consequently they followed much the same pattern as the l a t t e r (Fig. 2.2B, 2.3B, and 2.4). Again, two data groupings were evident (Fig. 2.4): 1) starved f i s h and f i s h fed every 14 days and 2) f i s h fed every 4 and 7 days. Although ammonia nitrogen excretion rates during SDA shared the pattern of oxygen consumption rates, the e f f e c t of acclimation i s r e l a t i v e l y greater. Maximum rates again occured during the f i r s t 24 hours following ingestion, however, f i r s t day ammonia nitrogen excretion rates in f i s h acclimated to meals weekly or every 4 days were two to three times those for starved f i s h or f i s h acclimated to meals every two weeks. Another difference occurred in the routine rate achieved after 4 days for f i s h acclimated to weekly meals (Fig. 2.2B). In these f i s h oxygen consumption attained a r e l a t i v e l y constant l e v e l , whereas ammonia nitrogen excretion declined markedly on the seventh day a f t e r being f a i r l y constant for the preceding 3 days. Estimates of t o t a l energy expenditure based on oxygen consumption (cal = 3.25 X mg oxygen consumed, Brett 1985) and energy expenditure due to protein catabolism (cal = mg ammonia 24 1 2 3 U 5 6 7 8 9 10 11 12 13 \U Days Post-prandial Figure 2.4. Ammonia nitrogen excretion of sa b l e f i s h acclimated to d i f f e r e n t feeding i n t e r v a l s . V e r t i c a l l i n e s through each mean equal one S.D. and sample sizes correspond to those in Figs. 2.5-2.8 25 nitrogen X 6.25 mg protein / mg ammonia nitrogen X 4.70 c a l / mg protein, Brett and Groves 1979) re f l e c t e d the proportional difference between oxygen consumption and ammonia nitrogen excretion rates and were compared to examine the metabolic fate of nutrients in f i s h given d i f f e r e n t feeding opportunities. For starved f i s h and f i s h fed every 14 days, t o t a l energy expenditure was always much greater than that attributable to protein catabolism (Fig. 2.5 and 2.6). Immediately following feeding the proportion of t o t a l metabolism represented by protein catabolism was greatest. This f r a c t i o n declined s t e a d i l y over 14 days then appeared to remain f a i r l y constant u n t i l day 24 of starvation. Beyond 24 days protein catabolism increased s l i g h t l y while t o t a l energy expenditure remained r e l a t i v e l y constant. Protein catabolism provided a much greater proportion of the metabolic fuel in the f i s h fed weekly and every 4 days (Fig. 2.7 and 2.8). In both cases the data suggested that, based on ammonia excretion, energy from protein catabolism s l i g h t l y exceeded t o t a l energy expenditure for the f i r s t two days, although the r e l a t i v e l y high variance of protein energy values indicated t h i s difference might not be r e a l . Beyond the second day, the proportion of t o t a l energy expenditure accounted for by protein catabolism declined, however, i t remained much greater than for starved f i s h and those fed every 14 days. 26 Figure 2.5. Total energy expenditure (based on oxygen consumption: squares) compared to that attributable to protein catabolism (based on ammonia nitrogen excretion: triangles) during starvation following a single meal. V e r t i c a l lines equal one S.D. and numbers are sample sizes which are the same for corresponding means. 27 ' • t I I I I I I I I I ) I 1 2 3 U 5 6 7 8 9 10 11 12 13 14 Days Post-prandial Figure 2.6. Total energy expenditure (based on oxygen consumption: squares) compared to that attributable to protein catabolism (based on ammonia nitrogen excretion: triangles) after acclimation to meals every 14 days. V e r t i c a l lines equal one S.D. and a l l sample sizes are 7. 28 400 320 JZ "5 240' u cu D TO c cu Q. X LU 160' c? (D C LU 80 1 2 3 Days Post-prandial Figure 2.7. Total energy expenditure (based on oxygen consumption: squares) compared to that attributable to protein catabolism (based on ammonia nitrogen excretion: triangles) after acclimation to meals every 4 days. V e r t i c a l l i n e s equal one S.D. and a l l sample sizes are 7. 29 40i 80 • M M MW Mt Mi • 1 2 3 4 5 6 7 Days Post-prandial Figure 2.8. Total energy expenditure (based on oxygen consumption: squares) compared to that attributable to protein catabolism (based on ammonia nitrogen excretion: triangles) after acclimation to weekly meals. V e r t i c a l l i n e s equal one S.D. and a l l sample sizes are 5. 30 2.3 DISCUSSION: Changes i n r o u t i n e m e t a b o l i c r a t e s have been a s s o c i a t e d wi th long term food d e p r i v a t i o n i n s e v e r a l f i s h s p e c i e s (Beamish 1964a, Mann 1965, DuPreez et a l . 1986) . S a b l e f i s h appear to share t h i s p h y s i o l o g i c a l c h a r a c t e r i s t i c ( F i g . 2.1) w i t h r o u t i n e oxygen consumption d e c l i n i n g s t e a d i l y i n s t a r v i n g f i s h and those fed once e v e r y two weeks. T h i s d e c l i n e of t o t a l energy e x p e n d i t u r e appears to s t o p a f t e r about 16 days of s t a r v a t i o n ( F i g . 2 . 5 ) . Once a c c l i m a t e d to meals e v e r y f o u r t h and seventh day , not o n l y i n i t i a l d i g e s t i v e metabo l i sm, but subsequent n o n d i g e s t i v e r o u t i n e metabol i sm i s c o n s i d e r a b l y g r e a t e r than i n p o o r l y fed f i s h ( F i g . 2 . 1 ) . Presumably i f these f i s h were a g a i n d e p r i v e d of food t h e i r m e t a b o l i c s t a t e would g r a d u a l l y f a l l to match t h a t of s t a r v e d i n d i v i d u a l s i n much the same manner as g r a d u a l a c c l i m a t i o n o c c u r r e d ( F i g . 2.2 and 2 . 3 ) . T h i s suggests an a d a p t i v e response to d i f f e r e n t f e e d i n g o p p o r t u n i t i e s . S i t u a t i o n s which p r o v i d e an adequate food s u p p l y for growth permi t an e l e v a t e d m e t a b o l i c s t a t e whereas those i n which food i s l i m i t e d r e q u i r e c u r t a i l e d m e t a b o l i c a c t i v i t y and c o n s e r v a t i o n of the r e s t r i c t e d energy s u p p l i e s , as h y p o t h e s i z e d by Paloheimo and D i c k i e (1966a) and K e r r (1982) . I t may be argued t h a t the apparent e l e v a t i o n of oxygen consumpt ion , both d u r i n g SDA and a t the r o u t i n e r a t e , i n f i s h fed weekly and e v e r y 4 d a y s , i s s i m p l y due to an a c c u m u l a t i o n of unprocessed m e t a b o l i t e s from incomple te SDA between f e e d i n g s . The c o n s t a n t r o u t i n e r a t e , a c h i e v e d on the f o u r t h day by f i s h fed weekly ( F i g . 2 . 1 ) , i n d i c a t e s t h i s i s not the c a s e . Had unprocessed m e t a b o l i t e s a c c u m u l a t e d , one would expect a s t eady 31 decline in oxygen consumption u n t i l the next feeding. Further, i f metabolites accumulated one might expect the maximum oxygen consumptions to r i s e beyond that observed and not reach a constant low-variance mean. As the active metabolic rate for sabl e f i s h of t h i s size i s about 600 mg oxygen/kg/hr (Furnell 1987), there is c l e a r l y scope for higher SDA, although c e l l u l a r or mitochondrial catabolic rates, rather that oxygen uptake rates, may l i m i t maximum SDA ( E l l i o t t 1979). If c e l l u l a r catabolism i s l i m i t i n g and metabolites accumulated, then i t i s not l i k e l y that f i s h fed every 4 days would have the same decline in SDA as f i s h fed weekly, but rather have the maximum SDA prolonged beyond 24 hours to eliminate the surplus metabolites. The a c t i v i t y information presented in chapter 3, coll e c t e d synchronously during these experiments, suggests that much of the elevation in t o t a l metabolism i s due to increased standard and a c t i v i t y metabolism. The change in metabolic status, with d i f f e r e n t feeding opportunities, is par a l l e l e d by a s h i f t in the energy sources used to power metabolism. The small proportion of t o t a l energy expenditure from protein catabolism in poorly fed f i s h (Fig. 2.5 and 2.6) becomes v i r t u a l l y the only source in f i s h fed weekly and every fourth day (Fig. 2.7 and 2.8). At a l l feeding levels the sabl e f i s h have a positive energy balance which declines in inverse proportion to the feeding i n t e r v a l (Table 2.1). This energy accumulation, however, d i f f e r s in composition between feeding treatments. In the following discussion, i t has been assumed, a p r i o r i , 32 T a b l e 2 . 1 . E n e r g y , p r o t e i n a n d l i p i d b u d g e t s , on a p e r m e a l b a s i s , f o r s a b l e f i s h w i t h d i f f e r e n t f e e d i n g o p p o r t u n i t i e s . P a r a m e t e r F e e d i n g I n t e r v a l 4 d a y s 7 d a y s 14 d a y s 1 ) P r o x i m a t e c o m p o s i t i o n o f f o o d : i ) P r o t e i n a ) g / m e a l 8 . 10 8 . 10 8 . 1 0 b ) k c a 1 / m e a 1 45 . 85 4 5 . 85 45 . 8 5 i i ) L i p i d a ) g / m e a l 2 . 00 2 . 00 2 . 0 0 b ) k c a l / m e a l 18 . 90 18 . 90 18 . 9 0 i i i ) T o t a l E n e r g y ( k c a l / m e a l ) 64 . 75 64 . 75 64 . 7 5 2) F a e c a l L o s s (5% o f p r o t e i n a n d l i p i d i n t a k e ) : i ) P r o t e i n a ) g / m e a l 0 . 41 0 . 41 0 . 41 b ) k c a l / m e a l 2 . 29 2 . 29 2 . 29 i i ) L i p i d a ) g / m e a l 0 . 10 0 . 10 0 . 1 0 b ) k c a l / m e a l 0 . 95 0 . 95 0 . 9 5 i i i ) T o t a l E n e r g y ( k c a l / m e a l ) 3 . 23 3 . 23 3 . 23 3) E x c r e t o r y l o s s ( b a s e d on ammon ia e x c r e t i o n ) : i ) Ammon ia N e x c r e t e d a ) g / m e a l 0 . 842 1 . 271 0 .675 b ) k c a l / m e a l 5 . 00 7 . 55 4 . 0 3 (g X 5 . 9 4 ) i i ) P r o t e i n c a t a b o l i z e d a ) g / m e a l 5 . 26 7 . 94 4 . 24 (g ammon ia N : X 6 . 2 5 ) b ) k c a l / m e a l 24 . 72 37 . 32 19 . 9 3 4) M e t a b o l i c e n e r g y e x p e n d e d ( b a s e d on o x y g e n c o n s u m p t i o n ) : i ) mg o x y g e n c o n s u m e d / m e a l i i ) k c a l e x p e n d e d / m e a l (mg X 0 . 0 0 3 2 5 ) 7464 24 . 2 6 1 1 8 6 6 38 . 56 1 6 2 7 7 52 . 90 5) P r o t e i n b a l a n c e ( r a t i o n - f a e c a l -c a t a b o l i z e d p r o t e i n ) : i ) g / m e a l i i ) k c a l / m e a l 2 . 4 3 - 0 . 2 5 3 . 4 5 1 3 . 7 5 - 1 . 4 2 1 9 . 5 3 6) E n e r g y b a l a n c e ( r a t i o n - f a e c a l -a m m o n i a - m e t a b o l i c e n e r g y ) : i ) k c a l / m e a l 3 2 . 2 6 1 5 . 4 1 4 . 59 7) L i p i d b a l a n c e ( d i e t - f a e c a l l i p i d -( m e t a b o l i c - p r o t e i n e n e r g y ) ) : i ) k c a l / m e a l i i ) g / m e a l 1 8 . 4 1 1 6 . 7 1 - 1 5 . 0 2 1 . 9 5 1 . 7 7 - 1 . 5 9 33 that f i s h are metabolizing a mixed l i p i d and protein substrate, and an o x y c a l o r i f i c equivalent of 3.25 cal/mg oxygen consumed applies (Brett 1985). Based on t h i s assumption, i t becomes clear that the l i p i d : p r o t e i n r a t i o i s a function of ration treatment and consequently the o x y c a l o r i f i c equivalent of 3.25 i s not exactly correct. Fortunately, the error i s not great (1 - 2% of t o t a l energy expenditure assuming an equivalent of 3.28 for l i p i d and 3.19 for protein, B r a f i e l d 1985) and does not a f f e c t the conclusions reached. Infrequently fed f i s h catabolize the least protein and derive much of their energy from l i p i d oxidation as indicated by the lower between-meal, t o t a l ammonia excretion seen in f i s h fed every two weeks (Table 2.1). A similar r elationship in the nitrogen consumption, excretion pattern has been observed by others (Gerking 1955, 1971, Savitz 1969, 1971, E l l i o t 1976b). Assuming a f i v e percent loss of protein and l i p i d energy in faeces (Pandian 1967a, b, Gerking 1955, 1971), there is a net protein gain of 3.45 g from each 8.1 g in a meal for f i s h fed every 14 days. This represents an energy gain of 19.5 kcal (3.45 g X 5.66 kcal/g), however, the t o t a l energy gain i s only 4.59 kcal . This means that the f i s h has a negative l i p i d balance of -15.0 kcal and i s consuming i t s body reserves. The f i s h fed every two weeks appear to be sparing protein and using a combination of endogenous and exogenous l i p i d s to power metabolism. Conversely, weekly fed f i s h show a negative protein balance, but a t o t a l energy gain that i s an order of magnitude greater than f i s h fed every two weeks. The negative protein balance may 34 be an a r t i f a c t of the high nitrogen excretion observed in the f i r s t two days post prandial for the two higher fed treatments (Fig. 2.4). Energy expenditure estimated from ammonia excretion ( i . e . protein catabolism) greater than that calculated from oxygen consumption (Fig. 2.7 and 2.8) cannot occur unless the f i s h operate anerobically involving gluconeogenesis from ammino acids, followed by g l y c o l y s i s , an u n l i k e l y and i n e f f i c i e n t process. There is also l i t t l e reason to expect anerobic metabolism given the low l e v e l of metabolic a c t i v i t y (Fig. 2.1) and high oxygen concentrations. A more l i k e l y explanation is the methodological r e s u l t of anomalous water analysis at high ammonia concentrations, which were extrapolated because they exceeded the standards in the c a l i b r a t i o n curve. None-the-less, on a per meal basis, weekly fed f i s h do appear to have a lower protein retention e f f i c i e n c y than the other two treatments. Despite the low or negative protein balance of weekly fed f i s h , they have a positive l i p i d balance of approximately the same magnitude as f i s h fed every four days and almost equal to a l l the l i p i d available in the d i e t . With weekly feedings the f i s h appear to have s u f f i c i e n t surplus protein such that excess can be used as a metabolic energy source while l i p i d becomes the preferred storage mater i a l . Fish fed every fourth day elaborate tissue both from l i p i d s and protein in the d i e t . The positive protein balance (2.43 g) represents 13.8 kcal of energy, 18.5 kcal less than the t o t a l energy balance. Again i t i s l i k e l y the ammonia analysis underestimated protein retention which may represent the 0.5 kcal of energy balance unaccounted for by protein retention and 35 d i e t a r y l i p i d energy. It i s d i f f i c u l t to speculate on the significance of the physiological strategies used by s a b l e f i s h to p a r t i t i o n energy intake in the d i f f e r e n t feeding environments. It appears that l i p i d is the preferred substrate of elaboration in well-fed f i s h when s u f f i c i e n t protein i s available in the d i e t . In f i s h fed weekly and every 4 days, protein catabolism can account for most energy expenditures. As feeding becomes less frequent, protein is retained and l i p i d s are used to power metabolism. The increase in ammonia excretion in f i s h starved beyond 24 days (Fig. 2.5) suggests that as l i p i d reserves become depleted, a greater proportion of t o t a l energy i s again derived from protein catabolism. The c o r r e l a t i o n of oxygen consumption and ammonia excretion rates suggests that SDA is associated with protein catabolism or amino acid deamination. The t o t a l SDA in a l l ration treatments, after acclimation, i s similar (Table 2.2), although the t o t a l energy balance, or growth rates, are quite d i f f e r e n t . This argues against the hypothesis that anabolic processes are the source of SDA. Conversely, the SDA observed i s d i r e c t l y 2 correlated (r =0.83) with protein balance, indicating the a s s i m i l a t i o n of protein, although not l i p i d , may account for some of the post-prandial elevation of oxygen consumption. It should, however, be noted that there is l i t t l e r e l a t i v e difference in SDA while protein balance calculations show a great r e l a t i v e difference between tretments. Consequently, the equation r e l a t i n g protein balance (X) to SDA (Y), (Y = 16.68(X) + 1539), 36 Table 2.2. Estimates of SDA and routine metabolic rate, on a per meal basis, for s a b l e f i s h with d i f f e r e n t feeding opportunities. Feeding Interval 4 days 7 days 14 days Routine oxygen consumption 64.5 61.5 43.7 rate (mg/kg/hr) SDA - t o t a l oxygen 1563 1539 1608 consumption above the routine rate between meals (mg) SDA - as a percent of 7.8 7.7 8.1 food energy consumed (assuming 3.25 cal/mg oxygen) indicates that when protein balance i s zero there i s s t i l l a s i g n i f i c a n t SDA consumption of 1539 mg of oxygen above the routine metabolic rate. From t h i s evidence, one would conclude that catabolic processes are the primary cause of SDA with a minor contribution from anabolism. The SDA for f i s h fed every two weeks i s derived from both protein and l i p i d catabolism. That for weekly fed f i s h r esults primarily from protein catabolism with a minor contribution from l i p i d s . SDA in f i s h fed every fourth day i s attributed almost exclusively to protein catabolism. In summary, these r e s u l t s i l l u s t r a t e the dynamic nature of metabolite handling and i t s dependence on the feeding state of experimental animals. Feeding history determines how sablefish respond to similar meals. This study also demonstrates the importance of monitoring experimental parameters to know when ration acclimation is achieved and v a l i d metabolic comparisons 37 can be made. Further, i t cannot be concluded that acclimation i s reached over the r e l a t i v e l y short term of experiments such as these. Obviously the f i s h fed every two weeks could not continue to deplete t h e i r l i p i d reserves and, although apparently acclimated, would have to eventually pursue another metabolite p a r t i t i o n i n g strategy. Simlarly, f i s h fed weekly could not indefinately elaborate tissue in the form of l i p i d without reaching a point of imbalance in proximate composition. Clearly these acclimation states are transient phases of r e l a t i v e s t a b i l i t y dependent on the past feeding history, the current l e v e l of n u t r i t i o n and future maintenance of the organism's v i a b i l i t y . 38 CHAPTER 3: THE EFFECT OF RATION ON THE ACTIVITY AND STANDARD METABOLISM OF SABLEFISH 3.0 INTRODUCTION: The r e s p i r a t o r y metabo l i sm of f i s h i s g e n e r a l l y r e c o g n i z e d as c o n s i s t i n g of t h r e e components: 1) a c t i v i t y , 2) d i g e s t i o n , and 3) s t a n d a r d metabo l i sm. T o g e t h e r , a c t i v i t y and s t a n d a r d metabo l i sm are r e f e r r e d to as r o u t i n e metabo l i sm (Warren and Davis 1967, F r y 1971, B r e t t and Groves 1979) which r e p r e s e n t s the energy e x p e n d i t u r e of s p o n t a n e o u s l y a c t i v e f i s h . The r o u t i n e and d i g e s t i v e m e t a b o l i c r a t e s of many f i s h have been r e p o r t e d (eg. Muir and N i i m i 1972, V a h l and Davenport 1979, and DuPreeze 1987) . The s t a n d a r d m e t a b o l i c r a t e has been l e s s s t u d i e d because i t r e q u i r e s an a d d i t i o n a l l e v e l of e x p e r i m e n t a t i o n to document, s p e c i f i c a l l y , synchronous a c t i v i t y and oxygen consumption measurements. The advantage of c o l l e c t i n g these a d d i t i o n a l data i s t h a t they a l s o y i e l d e s t i m a t e s of the energy f i s h are spending on a c t i v i t y e x c l u s i v e of the s t a n d a r d r a t e . T h i s i s u s u a l l y r e c o r d e d f o r f i s h under d i f f e r e n t l e v e l s of f o r c e d a c t i v i t y ( B r e t t 1964, 1965, B r e t t and G l a s s 1973, Beamish 1970) but r a r e l y for s p o n t a n e o u s l y a c t i v e f i s h (Beamish 1964b, c , Beamish and M o o k h e r j i i 1964) e s p e c i a l l y i n r e l a t i o n to an independent v a r i a b l e such as t emperature or r a t i o n l e v e l . The a c t i v i t y component of metabo l i sm i s u s u a l l y d e s c r i b e d i n terms of the energy e x p e n d i t u r e of f i s h swimming a t a s e r i e s of d i f f e r e n t v e l o c i t i e s i n a t u n n e l r e s p i r o m e t e r . By e x t r a p o l a t i n g to a l e v e l of no a c t i v i t y an e s t i m a t e can then be made of the 39 standard metabolic rate, the energy released by a resting, post-absorptive f i s h (Fry 1947). By examining swimming v e l o c i t y r e l a t i v e to energy consumption, one can estimate the most e f f i c i e n t swimming speeds. This leads to hypotheses on the swimming energy expenditures of wild f i s h (Ware 1975, 1978, Jones 1978, Kerr 1982). Unfortunately, t h i s approach gives l i t t l e information about the o v e r a l l energy expenditures of spontaneously active f i s h nor what controls their a c t i v i t y . It has been shown that wild f i s h would optimize growth by foraging at speeds giving the greatest energetic e f f i c i e n c y (Ware 1978). However, i f they do not swim continuously, no estimate can be made of their t o t a l a c t i v i t y energy expenditure without d e t a i l s of the temporal d i s t r i b u t i o n of a c t i v i t y . Further, the e f f i c i e n c y of swimming may be related to environmental food density where swimming at d i f f e r e n t speeds not only varies the expenditure of energy, but also the rate of energy intake and accumulation (Ware 1975). It would be reasonable to assume that the a v a i l a b i l i t y of prey might influence the energy f i s h spent swimming e s p e c i a l l y i f foraging was the primary a c t i v i t y expenditure (Kerr 1982). Although t h i s has been examined for f i s h a c t i v e l y feeding (Hunter and Thomas 1974), consideration must also be given to the time spent seeking prey between meals. Such a s i t u a t i o n may occur with mobile, schooling prey where predatory behavior while searching for contagiously d i s t r i b u t e d schools would be quite d i f f e r e n t than when feeding on them. A l t e r n a t i v e l y , prey can be located while resting and waiting. The primary objective of t h i s portion of the study was to examine the energy that s a b l e f i s h routinely 40 expend on locomotion when given d i f f e r e n t feeding opportunities. 3.1 Methods: A c t i v i t y measurements were made synchronously with the metabolic measurements described in chapter 2. Fish metabolic rates are often measured in small containers which r e s t r i c t the fishes' movements and do not allow the f u l l scope of spontaneous a c t i v i t y to occur. These experiments were conducted in 4000 L mass respirometers each equipped with two mechano-electric a c t i v i t y meters. The objective in using such large tanks for only f i v e , one kg f i s h per tank was to allow them f u l l opportunity to display spontaneous a c t i v i t y and avoid the r e s t l e s s darting and a g i t a t i o n often seen in confined f i s h . The tank's e l i p t i c a l shape presented no abrupt contour for the f i s h to negotiate in t h e i r normal c i r c u l a r swimming patterns. Observerations made while doing t a i l beat frequency counts showed the f i s h to be relaxed, usually swimmming slowly for varying periods up to 30 minutes, then resting for a short time on the bottom before resuming swimming. Tailbeat frequencies were recorded, after the PVC blanket covering the surface was removed, to compare swimming speeds between treatments. The observer and tank were covered by a black polyethylene tent which eliminated external disturbances. The f i s h swam in a burst and glide pattern. A b r i e f acceleration of 1-6 t a i l b e a t s would be followed by a coasting g l i d e . Individual observations were made for random lengths of time using a stopwatch. The observation period was in part controlled by the duration of a c t i v i t y . If the 41 observed f i s h rested 15 sec or less a f t e r a count started the res u l t was ignored as i t was d i f f i c u l t to make accurate counts of short duration. Individual recordings were generally 1 - 3 minutes in duration (X = 1.63 + 0.31 S.E. n = 1445). Between 5 and 15 individual observations were made during a 24 hr exper iment. A c t i v i t y data in t h i s paper are reported as counts per day. This represents the sum of counts for both meters in a tank. The a c t i v i t y meters used were designed to be simple, r e l i a b l e near s a l t water, and e a s i l y adjusted to increase or decrese s e n s i t i v i t y (Fig. 3.1). The meter was simply a nickel plated s t e e l rod suspended inside a copper tube. The end of the rod or pendulum was attached to a 0.5 kg breaking strength monofilament li n e which hung in the tank from the surface to one cm off the bottom. A lead weight of 15 g was attached to the end of the line and kept i t taut. When a f i s h struck the li n e or swirled the water near i t , the nickel plated pendulum was deflected and contacted the copper tube surrounding i t . Both the tube and pendulum were part of a single c i r c u i t which the contact completed. Contacts were recorded on an Easterline Angus event recorder. The s e n s i t i v i t y of the meter could be adjusted by a l t e r i n g the mass of the lead weight suspended from the monofilament l i n e , the diameter of the copper tube, or the thickness of the pendulum. The best configuration of the meter r e l i a b l y showed l i t t l e or no nocturnal a c t i v i t y , but substantial daytime a c t i v i t y , a pattern confirmed by v i s u a l observation. A 15 g lead weight with a 1.25 cm diameter copper tube was sa t i s f a c t o r y . By using two meters in each tank, more counts per 42 HOUSING LEAD WIRES BEDDED IN SILICONE SEALANT EVENT RECORDER JACKS 2.5cm WATER SURFACE 1.25cm DIA. COPPER TUBE -PENDULUM HOOK MONOFILAMENT LINE LEAD WEIGHT BOTTOM gure 3.1. The a c t i v i t y meter. day could be recorded without using excessively sensitive meters. T h e t w o m a s s r e s p i r o m e t e r s w e r e s e t u p a s m i r r o r i m a g e s o f e a c h o t h e r w i t h t h e a c t i v i t y m e t e r s a n d o t h e r e q u i p m e n t i n i d e n t i c a l p o s i t i o n s . M i n o r d i f f e r e n c e s i n e q u i p m e n t c o n f i g u r a t i o n m i g h t h a v e p r o d u c e d d i f f e r e n c e s i n t h e w a y t a n k s p a c e w a s u s e d b y t h e s w i m m i n g f i s h a n d i n f l u e n c e d t h e i r e n c o u n t e r r a t e w i t h t h e a c t i v i t y m e t e r s . T o f u r t h e r p r o t e c t a g a i n s t i n t e r t a n k d i f f e r e n c e s , t h e a c t i v i t y c o u n t s f o r e a c h e x p e r i m e n t a l f e e d i n g t r e a t m e n t w e r e r e c o r d e d e q u a l l y f r o m b o t h t a n k s . I f s l i g h t m e t e r d i f f e r e n c e s d i d o c c u r u n n o t i c e d d u r i n g t h e e x p e r i m e n t s , t h e y o n l y a d d e d t o t h e v a r i a b i l i t y o f t h e d a t a , n o t t o i n t e r t r e a t m e n t d i f f e r e n c e s . A c t i v i t y m e t e r s w e r e s w i t c h e d o n i m m e d i a t e l y a f t e r t h e l a s t w a t e r s a m p l e s w e r e t a k e n . T h e P V C c o v e r w a s g e n e r a l l y i n p l a c e f o r h a l f a n h o u r b e f o r e t h e m e t e r s w e r e t u r n e d o n i n o r d e r t h a t t h e s u r f a c e d i s t u r b a n c e d i d n o t a g i t a t e t h e f i s h . B y t h e e n d o f t h e e x p e r i m e n t s a l l f i s h w e r e h a b i t u a t e d t o c o v e r m a n i p u l a t i o n s a n d s h o w e d n o a l a r m . W h e n f i s h w e r e f e d , t h e c h o p p e d h e r r i n g w a s i n t r o d u c e d i n t o t h e t a n k s a n d t h e f i s h a l l o w e d t o e a t i t a l l (1 -2 m i n u t e s ) b e f o r e t h e a c t i v i t y m e t e r s w e r e e n g a g e d . T h e t a n k s a n d a l l a n c i l l a r y e q u i p m e n t w e r e c o m p l e t e l y e n c l o s e d i n b l a c k p o l y e t h y l e n e t e n t s t o p r e v e n t o t h e r a c t i v i t y i n t h e t a n k r o o m f r o m d i s t u r b i n g t h e f i s h a n d t o m a i n t a i n a 12 h r p h o t o p e r i o d . T a n k s w e r e n o t i n d i r e c t c o n t a c t w i t h t h e f l o o r , s o m o v e m e n t s i n t h e r o o m d i d n o t p r o d u c e v i b r a t i o n s i n t h e w a t e r . A c t i v i t y i n t h e r o o m d i d n o t c a u s e a n y a p p a r e n t r e s p o n s e s i n t h e f i s h w h e n o b s e r v e d f o r t a i l b e a t f r e q u e n c y c o u n t s . 44 The f i s h in each tank were fed meals of chopped herring (50 g per f i s h ) . Meal frequency was altered to simulate d i f f e r e n t feeding oportunities. Meal frequencies were: 1) every 4 days, 2) every 7 days, 3) every 14 days, and a replicated control series of f i s h starved for 8 weeks after the f i r s t meal. The number of meals was the same as in chapter 2 (Fig. 3.2). 3.2 RESULTS: Before beginning individual experiments a l l f i s h were starved for three weeks. Their a c t i v i t y was continuously monitored from the f i r s t feeding to the end of the experiment. A c t i v i t y counts taken from the f i r s t to the t h i r d or fourth feeding i l l u s t r a t e a period of acclimation in a c t i v i t y levels (Fig. 3.2) sim i l a r to those for oxygen consumption and ammonia excretion. I n i t i a l l y , spontaneous swimming a c t i v i t y gradually increased in a l l treatments at an equal rate (per feeding). Fish fed every two weeks reached a plateau of approximately 1100 a c t i v i t y counts per day by their t h i r d feeding ( i . e . 6 weeks). This l e v e l did not d i f f e r s i g n i f i c a n t l y over the remainder of the 12 week experiment. The d a i l y spontaneous a c t i v i t y of the f i s h fed every four and seven days continued to increase and become more variable. By the f i f t h feeding ( i . e . 5 weeks), the f i s h fed every seven days reached a plateau of 1761 counts per day whereas the f i s h fed every four days recorded an average 2134 counts per day after 3 weeks (Fig. 3.2). Discussion of the metabolic parameters in r e l a t i o n to ration requires defining when acclimation has occurred so that only 45 2800 LU to +1 a or LU a. to o o < 2 < LU 2400-2000-1600 1200 800 400 0 + • 11-FEEDING INTERVAL O 14 DAYS N= 14 • 7 DAYS N=7 * 4 DAYS N=4 3 4 5 6 7 8 9 FEEDING NUMBER 10 11 12 Figure 3.2. Average d a i l y a c t i v i t y counts for the 14, 7, and 4 day feeding intervals from the f i r s t feeding u n t i l the experiments ended. 46 post-acclimation values, where the f i n a l ration e f f e c t i s observed, are analyzed. The e f f e c t of acclimation on the mean d a i l y a c t i v i t y counts can be observed in F i g . 3.2. A gradual increase in counts per day occurs with consecutive feedings from the beginning of each treatment. The counts per day eventually reach asymptotes which can be considered the acclimated state. The f i r s t feeding at which acclimation was considered to have occurred was that which gave both greater and lesser values in subsequent feedings. Table 3.1 gives the number of pre-acclimation feedings and the number of post-acclimation feedings for each rati o n treatment. In the following discussion of treatment e f f e c t s , only post-acclimation data were considered. Table 3.1. D e f i n i t i o n of pre and post-acclimation feedings for d a i l y a c t i v i t y count data in the three ration treatments. Feeding Interval Pre-acclimation Post-acclimation Feedings Feedings 4 days 1, 2, 3, 4 5, 6, 7, 8, 9, 10, 11 7 days 1, 2, 3, 4 5, 6, 7, 8, 9 14 days 1, 2 3, 4, 5, 6, 7 Because an increase in d a i l y counts could be caused either by an increase in swimming v e l o c i t y or by longer periods of a c t i v i t y at constant v e l o c i t y , observations were made of ta i l b e a t frequencies in a l l treatments throughout the experiment. No s i g n i f i c a n t difference was found between days post-prandial within each treatment group (P(F = 0.51) > 0.25, DF = 3,24 - 4 day i n t e r v a l ; P(F = 0.77) > 0.25, DF = 6,28 - 7 day in t e r v a l ; P(F = 1.21) > 0.25, DF = 13,56 - 14 day i n t e r v a l ) . 4 7 S i m i l a r l y , when the re s u l t s for a l l days post-prandial were pooled to give a mean for each treatment group and the d i f f e r e n t treatments compared, no s i g n i f i c a n t difference in t a i l beat frequency was found (P(F = 0.95) > 0.25, DF = 2,130). Because the average d a i l y number of a c t i v i t y counts showed a treatment e f f e c t (Fig. 3.2), but t a i l b e a t frequency did not, the duration of a c t i v i t y or number of a c t i v i t y bouts per unit time were a function of ration l e v e l , but not the swimming v e l o c i t y . To estimate a c t i v i t y energy expenditure, both the oxygen consumption and a c t i v i t y of the f i s h were recorded. Total oxygen consumption was the sum of a c t i v i t y , digestive and standard metabolic rates (Fig. 3.3). It was, therefore, necessary to estimate and subtract standard and digestive metabolism from the t o t a l to calculate the a c t i v i t y component of metabolism. The sum of the digestive and standard metabolic rates was obtained by regressing the a c t i v i t y counts per day against the corresponding oxygen consumptions (Fig. 3.4, 3.5, and 3.6). This examination was made separately for each day post-prandial, in each treatment, because digestive metabolism was not constant, but gradually diminished to zero several days following a meal. The oxygen consumption intercept of each regression represented the combined energy expenditure made digesting food and on standard metabolism ( i . e . a c t i v i t y equals 0 at the Y-intercept). After digestion finished, the intercept became constant and represented the standard metabolic rate only (Line 4, F i g . 3.4; Line 4, F i g . 3.5, and Line 7, Fig 3.6). For each ration treatment and each day post-prandial the combined digestive and standard 48 100 10' U t l l l l t l l l l l l l l 1 2 3 4 5 6 7 8 9 10 11 12 13 U 15 DAYS POST-PRANDIAL Figure 3.3. Mean t o t a l metabolism (oxygen consumption) for sa b l e f i s h , each day post-prandial, when acclimated to i d e n t i c a l meals fed every 4, 7, and 14 days. 49 100 1000 2000 300C ACTIVITY COUNTS PER DAY Figure 3 . 4 . Regressions of oxygen consumption and a c t i v i t y counts over the digestive period for s a b l e f i s h acclimated to meals every 4 days. 50 1001 — I — 1 ' 1000 2000 3000 A C T I V I T Y C O U N T S P E R D A Y Figure 3.5. Regressions of oxygen consumption and a c t i v i t y counts over the digestive period and afterward for sabl e f i s h acclimated to meals every 7 days. The regressions for days 4 to 7 post-prandial are i d e n t i c a l and pooled. 5 1 80 Figure 3.6. Regressions of oxygen consumption and a c t i v i t y counts over the digestive period for s a b l e f i s h acclimated to meals every 14 days. The regressions for days 7 to 14 have been pooled as digestion was complete. Also included i s the regression for the l a s t month of observations on starved f i s h . 52 metabolic rates are i l l u s t r a t e d in F i g . 3.7. The standard errors in t h i s figure were the standard errors of the regression intercepts (Fig. 3.4, 3.5, and 3.6). Fish fed every two weeks had a considerably lower combined rate on any given day post-prandial than f i s h fed every four and seven days, which in turn were s i m i l a r . By subtracting these values from t o t a l metabolism (Fig. 3.3), the a c t i v i t y component of metabolism for each treatment in each day post-prandial was estimated (Fig. 3.8). Before examining the differences in a c t i v i t y metabolism between rati o n treatments, i t was of interest to consider whether the mean d a i l y a c t i v i t y counts, within each treatment, changed with time since feeding (Table 3.2). Analysis of variance of the f i s h fed every four and seven days demonstrated that the mean a c t i v i t y counts per day were the same on a l l days post-prandial (P(F = 0.173) = 0.932, DF = 3,24; P(F = 0.864) = 0.534, DF = 6,28 for 4 and 7 day feeding intervals r e s p e c t i v e l y ) . This, however, was not the case for the f i s h fed every two weeks. These f i s h displayed a r e l a t i v e l y constant a c t i v i t y u n t i l the tenth day post-prandial after which a marked decrease occurred (Table 3.2). Control f i s h , starved after the f i r s t feeding, showed low a c t i v i t y l e v e l s with considerable v a r i a t i o n . No values were given for the starved f i s h prior to 20 days post-prandial because only two data points were available for each day and therefore no credible S.E. could be computed. The two-point means were, however, similar to those after 20 days post-prandial. The a c t i v i t y component of t o t a l metabolism, calculated as the difference between t o t a l metabolism (Fig 3.2) and the sum of digestive and standard metabolism (Fig. 3.7), i s i l l u s t r a t e d for 53 100 90-801 70-g 6 0 ' _ i o < u. 501 2£ Lo 40' 30' 20 < FEEDING INTERVAL O 4 DAYS n=7 • 7 DAYS n=5 • 14 DAYS n=5 3 10H » V I I | l l l t | l l 4 5 6 7 8 9 10 11 12 13 14 15 DAYS P O S T - P R A N D I A L Figure 3.7. Standard and digestive metabolism of sabl e f i s h acclimated to meals every 4, 7, and 14 days over the between meal period. Data points are the intercepts of regression lines in Fi g . 3.4-3.6 with the S.E. of the intercept. Sample sizes (n) are the number of points used in the regression. 54 15' U-13' 12' FEEDING INTERVAL O U DAYS • 7 DAYS • H DAYS „ 11 or \ Q. to o <£ 6i LU s 51 >-t= 4i 2' 1. o 5 6 7 8 9 10 11 12 13 U 15 DAYS POST-PRANDIAL Figure 3.8. A c t i v i t y component of t o t a l metabolism in sablefish acclimated to meals every 4, 7, and 14 days over the between meal period. Data points represent the difference between points in F i g . 3.3 and 3.7. 55 Table 3.2. Mean a c t i v i t y counts per day for each day post-prandial in the three ration treatments and for days 20-52 post-prandial for starved f i s h . Days Post- Mean A c t i v i t y Counts per Day (+_ S.E.) Prandial Feeding Interval 4 days 7 days 14 days Starved (n = 7) (n= 5) (n = 5) 1 2192 (64) 1803 (231) 1213 (49) 2 2158 (214) 1591 (285) 1263 (157) 3 2145 (147) 2063 (275) 1050 (173) 4 2041 (164) 1636 (137) 1270 (131) 5 - 1973 (107) 1300 (164) 6 - 1772 (178) 1111 (62) 7 - 1506 (250) 1217 (156) 8 - 1126 (163) 9 - 1578 (201) 10 - 1327 (141) 11 - 911 (128) 12 - 752 (150) 13 - 487 (133) 14 - 795 (204) 20 - 531 (102) 22 - 791 (223) 24 - 482 (152) 26 - 223 (101) 28 - 996 (64) 30 - 545 (189) 32 - 1078 (281) 34 - - - 661 (285) 40 - 701 (124) 44 - 814 (224) 48 - 600 (170) 52 - - - 290 (130) each rat i o n treatment in F i g . 3.8. The decline in a c t i v i t y counts per day post-prandial, observed in Table 3.2 for f i s h fed every 14 days, was re f l e c t e d in the d i s t r i b u t i o n of a c t i v i t y metabolism measurements between feedings. If the means of these points were calculated for each treatment and plotted against rati o n , expressed in conventional d a i l y units (Fig. 3.9), i t is 56 121 " 1 I • r 0.2 0.4 0.6 0.8 1.0 1.2 DAILY RATION {% WET BODY WEIGHT) Figure 3.9. A c t i v i t y component of sa b l e f i s h ^ a b o l i s m when starved and when acclimated to meals every 4, 7, and 14 days as a l u n c t t o n of ra t i o n expressed on a d a i l y basis. Means are from the data in F i g . 3.8. 57 apparent that rat i o n d i r e c t l y influenced the l e v e l of a c t i v i t y . Also in t h i s figure were estimates for the starved f i s h which were not included in F i g . 3.8 as they give an unwieldy abcissa ( i . e . up to 52 days postprandial). Of note was the proportion of t o t a l metabolism (Fig. 3.3) devoted to a c t i v i t y (Fig. 3.9). In a l l cases a c t i v i t y metabolism was less than 20% of the average hourly expenditure. This occurred despite observations that the f i s h were generally active throughout the day, spending r e l a t i v e l y l i t t l e time resting on the tank bottom. The f i s h were, however, d i u r n a l l y active and showed only s l i g h t nocturnal a c t i v i t y . Consequently, because hourly oxygen consumption was measured as a 24 hour average and the photoperiod was 12 hours, the a c t i v i t y energy expenditure while the f i s h were a c t u a l l y swimming was about twice that i l l u s t r a t e d in F i g . 3.9. The standard metabolic rate of the f i s h could also be estimated from Figs. 3.4, 3.5, and 3.6. The standard metabolic rate was the oxygen consumption intercept of the lowest l i n e in these figures which was measured afte r digestion was complete and no longer contributed to t o t a l metabolism. Again, ration appeared to exert a strong c o n t r o l l i n g influence over standard metabolism (Fig. 3.10) despite the fact that t h i s was usually considered constant given one f i s h size and temperature. Standard metabolic rate constituted a much larger proportion of the t o t a l metabolism than a c t i v i t y expenditures. Estimates of routine metabolic rate (Fig. 3.11) were simply the sum of a c t i v i t y and standard metabolism or the average t o t a l metabolism aft e r digestion had stopped (Fig. 3.2). The ef f e c t of 58 Figure 3.10. Standard metabolism of s a b l e f i s h acclimated to meals every 4, 7, and 14 days and starved f i s h as a function of ratio n expressed on a d a i l y basis. Means are based on the intercepts of post-digestive regressions in F i g . 3.4 - 3.6. Data for starved f i s h are for days 20 - 52 post-prandial (Fig. 3.6). 59 Figure 3.11. Routine metabolism of s a b l e f i s h acclimated to meals every 4, 7, and 14 days and starved f i s h as a function of ration expressed on a d a i l y basis. Means are based on the sum of data points used to estimate the means presented in F i g . 3.9 and 3.10. 60 r a t i o n on the routine metabolic rate i s of the same form as observed for a c t i v i t y and standard metabolism, although the curvature of the l i n e i s r e l a t i v e l y greater. 3.3 DISCUSSION: The t h e o r e t i c a l swimming energy expenditures of pelagic f i s h have been examined by Ware (1975, 1978). He suggests two levels of a c t i v i t y may optimize growth: 1) c r u i s i n g speed which gives the greatest distance per unit energy, and 2) foraging speed which gives the greatest net energy gain. The l a t t e r includes not only variables for the swimming energy expenditure, but also the prey concentration. It i s d i f f i c u l t to apply these d i s t i n c t i o n s to s a b l e f i s h which have been reported consuming large prey items infrequently (Sullivan and Smith 1982). Is the time spent searching between meals best described as c r u i s i n g or foraging? From Ware's analysis i t i s apparent that as prey density decreases, the optimal c r u i s i n g and foraging speeds converge. Consequently there i s l i k e l y l i t t l e difference between these values for infrequently fed s a b l e f i s h . The lack of difference in t a i l beat frequencies, either between days post-prandial within ration treatments or between ration treatments, indicates that the s a b l e f i s h in these experiments moved at a constant speed. Although t a i l beat frequencies were recorded for d i f f e r e n t known v e l o c i t i e s in a tunnel respirometer (Furnell 1987), these v e l o c i t i e s cannot be applied to s a b l e f i s h swimming in the mass respirometers. In these large tanks the f i s h swam with a burst and glide pattern; in the swimming tunnel the f i s h used a steady t a i l beat. Burst 61 and glide swimming i s up to 50% more e f f i c i e n t than steady swimming (Weihs 1974, Blake 1983). It i s therefore impossible to estimate swimming speed in the mass respirometers from t a i l beat frequencies or relate i t to corresponding energy expenditures in the swimming tunnel. It i s , however, s i g n i f i c a n t that the t a i l beat frequencies were the same in a l l treatments at a l l times. It appears that s a b l e f i s h in the d i f f e r e n t treatments were pursuing a sin g l e , perhaps optimal c r u i s i n g speed and that they varied a c t i v i t y periods to change their energy expenditures. This would suggest that in the presence of more abundant food, sabl e f i s h have evolved to benefit from more persistent searching, but at a speed which gives the greatest distance or p r o b a b i l i t y of prey encounter for the energy expended. The l e v e l of a c t i v i t y ( i . e . counts per day) did not d i f f e r over the feeding i n t e r v a l for the f i s h fed once every 4 and 7 days, but those fed every 14 days displayed a decrease in a c t i v i t y toward the end of the i n t e r v a l (Table 3.2, F i g . 3.8). This further confirms the a c t i v i t y - r a t i o n r e l a t i o n s h i p observed between treatments. The decline of a c t i v i t y in f i s h fed every two weeks suggests an attempt to conserve limited energy stores. The re s u l t s presented in chapter 2 indicate that f i s h fed every two weeks had a s l i g h t l y positive energy balance (Table 2.1). Their energy balance may have been negative had they not reduced a c t i v i t y during the l a t t e r part of the two week feeding i n t e r v a l . Much t h e o r e t i c a l consideration has been given to the existence of a rela t i o n s h i p between a c t i v i t y and ration in f i s h (Kerr 1971a, 1971b, 1971c, Ware 1972, 1975, 1978, Jones 1978, Majkowski and Waiwood 1981). Kerr (1982) suggested a d i r e c t 62 p r o p o r t i o n a l i t y between food intake and a c t i v i t y expenditures. Ware (1978) hypothesized a r e l a t i o n s h i p between prey density and swimming speed as implied by Jones (1978). In these approaches there i s an assumption of f a i r l y constant a c t i v i t y , although Ware (1975) estimated the period of a c t i v i t y in a reanalysis of Ivlev's (1960) data on foraging in Alburnus. Winberg (1956) suggested that the routine energy expenditure of wild f i s h was constant at approximately twice the standard metabolic rate. Esitmates as high as four times the standard rate have been suggested as have rates as low as 1.5 times standard metabolism (Ware 1978). These experiments indicate that control of the a c t i v i t y period i s the sablefish's primary means of modulating their a c t i v i t y energy expenditure. More importantly, the average routine post-digestive metabolism i s on the order of not more than 1 . 4 times the standard rate when well fed f i s h are most active during the day, and considerably less when poorly fed and a c t i v i t y is averaged over 2 4 hours (Fig 3.3 and 3.7). These low values for a c t i v i t y might be attributed to the difference between spontaneously active f i s h in c a p t i v i t y and those in the wild. It should, however, be noted that s a b l e f i s h in the mass respirometers were by no means in a c t i v e . The well fed f i s h were a c t i v e l y swimming the majority of the time when observed for t a i l beat frequencies. Poorly fed f i s h rested more frequently, but when active were indistinguishable from well fed f i s h . It is d i f f i c u l t to believe that well fed wild f i s h could be active more frequently than well fed experimental f i s h unless they were also active a l l night. It i s possible that wild f i s h swim faster 63 giving routine to standard metabolic rate r a t i o s of 2 or more. This would, however, not be in agreement with optimal swimming speed theory nor the constant swimming speeds observed in these experiments. Thus, i t i s e n t i r e l y possible that s a b l e f i s h in nature spend as much energy swimming as captive f i s h in large mass respirometers (Jones 1978). The r e l a t i o n s h i p between ration and the routine metabolic rate has the same, two-state form that the metabolite processing information showed in chapter 2 (Fig 3.11). The routine rate consists of the a c t i v i t y and standard components and the two state system i s most obvious in the standard rate (Fig. 3.10). A c t i v i t y metabolism has a near linear r e l a t i o n s h i p with ration (Fig 3.9) as proposed by Kerr (1982). It i s not unreasonable to expect a r e l a t i o n s h i p between standard metabolic rate and the l e v e l of c i r c u l a t i n g and c e l l u l a r metabolites, even in post-digestive f i s h . The res t i n g , post-digestive metabolic rate of s a b l e f i s h (as standard metabolism i s defined) is a function of long term ration history. Standard metabolic rates are useful for investigating the e f f e c t of external variables such as weight and temperature on metabolism where some standard i s required for comparison. They are not, however, useful in an eco l o g i c a l context without some consideration given to what constitutes a standard rate. These results raise the question; when i s a f i s h in a post-absorptive state? It i s apparent when the primary process of digestion ends (Fig 3.7), but not when the biochemical consequences of elevated c i r c u l a t i n g metabolites and probably hormones reach a steady state, i f ever. The difference in the standard metabolic rates 64 of well and poorly fed f i s h may r e f l e c t a difference in rates of tissue turnover ( i . e . combined catabolic and anabolic metabolism). The gradual decline of the combined standard and digestive metabolic rates, in f i s h fed every two weeks (Fig 3.7), further argues the d i f f i c u l t y of defining a post-absorptive state. In summary, i t i s apparent that the a c t i v i t y component of t o t a l metabolism may play a much less s i g n i f i c a n t part in energy budgeting than previously thought and i t is a function of r a t i o n . Further, standard metabolism is not constant in a l l feeding situations and can represent a large proportion of the fishes t o t a l metabolic expenditure. The impact of these findings on the modeling of s a b l e f i s h energetics i s considerable. 65 CHAPTER 4: PARTITIONING OF LOCOMOTOR AND FEEDING METABOLISM IN SABLEFISH 4.0 INTRODUCTION: It i s widely recognized that the aerobic metabolism of fishes can be separated into three general components: R = Rs + Rd + Ra (Brett and Groves 1979, Priede 1985) where R i s t o t a l respiratory metabolism (mg oxygen/kg/hr). The minimum l e v e l of respiratory metabolism (Rs), the standard metabolic rate, i s the oxygen consumption of a resting, unfed, unstressed f i s h (Fry 1947). The upper l i m i t i s defined as the maximum sustained rate of oxygen uptake (Brett and Groves 1979). The difference between these l i m i t s i s the fi s h ' s metabolic scope (Fry 1947). Energy production greater than the metabolic scope can occur for short periods when anerobic metabolism i s used, however, th i s state cannot usually be maintained for long and an oxygen debt i s generally made up afterward. The term SDA (Rd) has a plethora of functions ascribed to i t (Muir and Niimi 1972, Beamish 1974, Kleiber 1975, Brett 1976, Tandler and Beamish 1979). These are reviewed by Jobling (1981) who concluded that the majority of SDA energy is expended on biochemical degradation of metabolites and the synthesis of protein. Regardless of i t s cause, SDA i s observed as an elevation of oxygen consumption immediately following a meal and continuing for various periods of time. The t o t a l elevation of oxygen consumption and the duration of the e f f e c t are correlated 66 with ration s i z e , q u a l i t y ( e s p e c i a l l y protein content) and temperature (Saunders 1963, Muir and Niimi 1972, Vahl and Davenport 1979, Jobling and Davies 1980). In most fishes the maximum l e v e l of SDA is between 1.5 and 2.5 times the standard metabolic rate (Jobling 1981) and in some species can represent a large proportion of the metabolic scope (Soofiani and Hawkins 1982). A c t i v i t y metabolism can account for a l l the metabolic scope in many species (Brett 1964, Brett and Groves 1979) and most of i t in others (Soofiani and Priede 1985). Clearly, f i s h are faced with a budgeting problem when the demands from SDA and a c t i v i t y exceed the aerobic metabolic scope (Priede 1985). Behavioral a l l o c a t i o n mechanisms such as feeding then resting have been proposed for some species (Vahl and Davenport 1979), however, these are opportunistic in nature and can only operate when circumstances permit. Faced with a need for a c t i v i t y immediately following a meal, i t would be advantageous for a f i s h to have a physiological mechanism a l l o c a t i n g aerobic metabolism to locomotion. The objective of t h i s study was to examine the possible existence of such a mechanism by imposing simultaneous SDA and swimming metabolic loads. 4.1 METHODS: To define the duration of SDA, fi v e preweighed s a b l e f i s h ("X = 0.993 kg + 0.012 S.E. N = 10) were placed in each mass respirometer and held at the i r prescribed acclimation temperature and photoperiod. They were fed weekly with 50 g of chopped herring per f i s h . To determine metabolic rate, the p l a s t i c 67 covers were placed over the tanks, the water flow c u r t a i l e d and heat exchangers engaged. Oxygen consumption was determined from the difference between an i n i t i a l oxygen sample and another 24 hours l a t e r . Ammonia concentrations were synchronously monitored (Indophenol method, Strickland and Parsons 1972); they did not exceed 0.46 ppm t o t a l ammonia and were usually less than 0.1 ppm. This i s below a l e v e l considered c h r o n i c a l l y toxic in marine fishes (Haywood 1983) and no toxic symptoms were observed in these experiments. To impose the dual metabolic load of a c t i v i t y and SDA and to es t a b l i s h the standard metabolic rate in the c l a s s i c manner, three f i s h were tested in the same tunnel respirometer described by Brett (1964) at a l l but the e a r l i e s t stage of digestion. I n i t i a l l y , in the swimming tunnel experiments, after acclimation to weekly meals, each f i s h was starved for 300 hr (to ensure a post-digestive s t a t e ) , anesthetized (2-phenoxy ethanol) and weighed, placed in the respirometer, and allowed to acclimate for 24 hours. Its oxygen consumption was then measured in one-half-hour runs at d i f f e r e n t swimming speeds. Determinations were also made for inactive f i s h . This was possible because s a b l e f i s h lack a swim bladder, are consequently negatively buoyant and w i l l often rest on the bottom of the tunnel chamber at current v e l o c i t i e s up to 15 cm/sec. During these runs, the f i s h were observed continuously and the run restarted i f the s l i g h t e s t locomotor movement was observed. The respirometer was flushed and current stopped for at least one-half-hour between runs. Fish were brought up to the test v e l o c i t y and held there for 15 68 min before the water supply was closed and the f i r s t oxygen sample taken. Data from these unfed f i s h ensured obtaining the oxygen consumption for f i s h with only the metabolic demands of swimming a c t i v i t y . Following these i n i t i a l runs, each of the three o r i g i n a l f i s h was given a 50 g meal of chopped herring and, af t e r s i x hours, anesthetized and transferred to the tunnel respirometer. The six-hour delay was intended to reduce the p o s s i b i l i t y of f i s h regurgitating the meal. Calculation of oxygen consumption was based on the pre-feeding weight of the f i s h . Every f i s h was allowed 18 hours to acclimate to the respirometer and experimental runs started 24 hours aft e r feeding. Each day for up to s i x days ( i . e . 150 hr post-prandial) the f i s h in the respirometer was forced to swim at four d i f f e r e n t speeds, for one-half-hour, and i t s oxygen consumption determined. As before, determinations were also made for the f i s h while inactive. The highest imposed swimming v e l o c i t y was selected on the c r i t e r i o n that v e n t i l a t o r y rate returned to the normal resting state within one minute of the run's end. This was later determined to be equivalent to approximately 60 percent of the maximum sustained metabolic rate. Subsequent monitoring of the post-run oxygen consumption rates (15 - 120 min post-run) showed them not s i g n i f i c a n t l y d i f f e r e n t from well rested inactive f i s h in a simi l a r digestive state. It was therefore assumed that a l l oxygen consumption rates represented aerobic metabolism only. Data from these experiments gave the oxygen consumption of f i s h facing the double metabolic load of SDA and forced a c t i v i t y throughout the digestive process and for a short time afterward. 69 4.2 RESULTS: Information from the mass respirometers (Fig. 4.1), col l e c t e d before and independently of that for weekly fed f i s h in the previous chapters, demonstrated the course of SDA (corresponding to a weekly 50 g meal of chopped herring per fish) spanned approximately 4 days. While in the mass respirometers the f i s h swam s t e a d i l y and slowly during the day with a burst and glide pattern showing a s l i g h t decrease in swimming immediately after feeding. Swimming a c t i v i t y was greatly reduced during the 12-hr night. Analysis of variance indicated there was a highly s i g n i f i c a n t difference between mean oxygen consumption data when broken into 20-hr post-prandial blocks (P(F)<0.0005). The 20-hour blocks were selected as they gave similar sample sizes for each block. There was, however, no s i g n i f i c a n t difference between means, of 20-hr time blocks, from 100 to 180 hr post-prandial (0.10>P(F)>0.05). The grand mean of these l a s t four time blocks was 62.0 mg oxygen/kg/hr (+.0.81 S.E. N=18) and t h i s can be taken as the 24-hr routine metabolic rate consisting of standard and routine swimming oxygen demands. The maximum oxygen consumption was observed in the f i r s t time block after feeding and was 89.4 mg oxygen/kg/hr (+.1.6 S.E. N=4). Hence the maximum elevation of oxygen consumption due to SDA was approximately 1.4 times the routine rate. It i s l i k e l y that the maximum oxygen consumption exceeded t h i s but was of too short duration to be determined in such large respirometers. The r e s u l t s from the tunnel respirometer were intended to, 1) provide a comparison between the oxygen consumption of f i s h operating with only a locomotor oxygen demand and f i s h facing 70 0) cn o 2 0 10 20 AO 60 80 100 120 140 160 180 Hours Post-prandial Figure 4.1. Oxygen consumption of s a b l e f i s h in a 4000 L mass respirometer at 8.5 C following a 50 g meal of chopped herring. The a c t i v i t y component of metabolism is the difference between the routine post-prandial rate of oxygen consumption and the standard rate. V e r t i c a l l i n e s on the bar tops equal one S.D.. 71 both SDA and locomotor oxygen demand and 2) provide a standard metabolic rate to compare with that obtained in the mass respirometers. The duration of SDA, determined in the mass respirometer, indicated when digestion ended. Swimming tunnel data have therefore been separated into two categories: 1) digestive--for f i s h influenced by SDA from 24 to 100 hr post-prandial and 2) non- d i g e s t i v e — f o r f i s h not influenced by SDA from 101 to 300 hr post-prandial (Fig. 4.2). For each category a separate regression was preformed using the natural logarithm of oxygen consumption as the dependent variable and swimming v e l o c i t y as the independent variable. These are the li n e s plotted in F i g . 4.2. S t a t i s t i c s for the two regressions are: 1) Non-digestive f i s h Ln (mg oxygen/kg/hr) = 3.395 (velocity (m/sec)) + 4.058 Zero v e l o c i t y intercept = 57.9 (52.5 - 63.8 = 95% C.I.) 2 r = 0.936 N = 38 2) Digestive f i s h Ln (mg oxygen/kg/hr) = 2.685 (velocity (m/sec)) + 4.426 Zero v e l o c i t y intercept = 83.6 (78.2 - 89.4 = 95% C.I.) 2 r = 0.937 N = 43 The slopes of the two regressions are highly s i g n i f i c a n t l y d i f f e r e n t (P(t)<0.001) as are the intercepts (P(t)<0.001). The regression l i n e s intersect at an oxygen consumption rate of 335.8 mg/kg/hr and a swimming v e l o c i t y of 0.518 m/sec (approximately one body length per sec). The standard metabolic rate, based on the oxygen consumption of inactive f i s h from 100-300 hr post-prandial was 52.8 mg/kg/hr (+2.2 S.E. N=ll). This i s 5.1 72 Figure 4.2. Oxygen consumption of sa b l e f i s h in a tunnel respirometer at 8.5 C. Open c i r c l e s represent f i s h starved for >100 hr (non-digestive) and dots represent f i s h from 24-100 hr post-prandial (digestive). Lines A and B represent the natural log linear regressions for non-digestive and digestive f i s h respectively. Zero v e l o c i t y data are given as means with one S.D. Data are for three f i s h and 81 separate determinations. 7 3 mg/kg/hr less than the zero v e l o c i t y oxygen consumption intercept of the regression for non-digestive f i s h , comparable to that estimated in chapter 3 for f i s h fed every week in the mass respirometer and probably a better estimate of actual standard metabolic rate. The standard metabolic rate (52.8 mg/kg/hr) has been superimposed on the mass respirometer data (Fig. 4.1). When thi s i s subtracted from the routine metabolic rate of post-digestive f i s h in the mass respirometers (62 mg/kg/hr) the difference, 9.2 mg/kg/hr, represents the oxygen consumption due to routine swimming a c t i v i t y over 24 hr and agrees well with the re s u l t s in chapter 3. As the f i s h were r e l a t i v e l y inactive during the 12 hr of darkness, l i t t l e energy was expended swimming. Hence, oxygen consumption while spontaneously swimming i s l i k e l y closer to double the 24-hr a c t i v i t y metabolic component or about 18 mg/kg/hr. 4.3 DISCUSSION: One of the most noteworthy findings of t h i s experiment is the intersection of the oxygen consumption versus swimming v e l o c i t y curves for digestive compared with non-digestive s a b l e f i s h (Fig. 4.2). If Rd and Ra were additive over the metabolic scope of s a b l e f i s h , no intersection would occur and the li n e s would be c l e a r l y distinguishable. That i s , when oxygen consumption was plotted against swimming v e l o c i t y , the intercepts of the two regressions would d i f f e r , but the slopes would be equal, giving i d e n t i c a l curves separated by a constant oxygen consumption corresponding to the average SDA. In these experiments, the regressions for non-digestive and digestive f i s h had v i r t u a l l y i d e n t i c a l c o e f f i c i e n t s of determination indicating a log linear r e l a t i o n s h i p explained 94% of the v a r i a t i o n in both data sets. The intersection of these l i n e s would suggest that as swimming oxygen demand increases, the proportion allocated to digestion decreases u n t i l swimming consumes a l l of the metabolic scope. The active metabolic rate for similar size s a b l e f i s h at the temperatures examined corresponds to a v e l o c i t y of 1.37 (+ 0.07 S.E. N=5) body lengths per sec (Brett, unpublished data). For f i s h used in these experiments, t h i s corresponds to a swimming v e l o c i t y of 0.685 m/sec and an oxygen consumption rate of 592 mg/kg/hr. Clearly, the intersection of the digestive and non-digestive power preformance curves f a l l s within t h i s range, occurring at 57% of the active oxygen consumption rate. The intersection of these curves implies that at v e l o c i t i e s greater than the intersection point, non-digestive f i s h a c t u a l l y have a higher oxygen demand than digestive f i s h . Although i t seems un l i k e l y , t h i s cannot be refuted by the present data as only one datum was taken much beyond the intersection v e l o c i t y . It may be argued that i f swimming metabolism reduced digestive metabolism, i t would not be possible for a routinely active f i s h to digest i t s food. It must, however, be noted that routine a c t i v i t y metabolism (Fig 3.9 and 4.1) i s very low. Consequently, under routine conditions, both normal swimming a c t i v i t y and digestion could occur synchronously. When greater swimming a c t i v i t y was required, digestion would diminish. In similar experiments with largemouth bass (Micropterus salmoides), Beamish 75 (1974; F i g . 3) observed no reduction in SDA as swimming v e l o c i t y increased. Sablefish are constantly mobile, pelagic f i s h whereas largemouth bass are ambush predators with irregular bursts of a c t i v i t y . Perhaps such a shunting mechanism i s required only in species which constantly balance the double metabolic load of swimming and digestion within t h e i r metabolic scope. The indication of a physiological mechanism which allocates oxygen to swimming over digestion raises the question of what the mechanism may be. Studies by Daxboeck (1981) and Randall and Daxboeck (1982) suggest that swimming a c t i v i t y in Salmo gairdneri causes a reduction in blood flow to the l i v e r , spleen, and stomach while markedly increasing i t to red muscle t i s s u e . The factors leading to t h i s r e a l l o c a t i o n are unknown. The consequences of such a r e d i s t r i b u t i o n agree with the findings here. The stomach and l i v e r are the main s i t e s of digestion and metabolite catabolism, respectively, hence a reduction in blood flow could e a s i l y l i m i t the oxygen consumption attr i b u t a b l e to digestion. In summary, i t appears that a physiological mechanism exists whereby s a b l e f i s h are able to a l l o c a t e their oxygen supply to locomotion when the oxygen demand from both digestion and locomotion exceeds a threshold value. 76 CHAPTER 5: GENERAL DISCUSSION The relationships between ration and a c t i v i t y metabolism and ration and standard metabolic rate are of significance from both ecological and physiological perspectives. Although the existence of these relationships had been suspected, there were never d i r e c t tests of them. If f i s h , and other organisms, are considered as s e l f sustaining chemical reactions s t r i v i n g to maintain homeostasis in a variable environment, i t i s not surprising to find physiological energy p a r t i t i o n i n g mechanisms which d i r e c t limited supplies into areas y i e l d i n g the greatest sustaining return, either through conservation or expenditure. It i s , however, in s t r u c t i v e to consider the options that are pursued and their consequences. It i s impossible to relate the a c t i v i t y observed in the tanks to f i s h in nature. It is also currently impossible to preform t h i s detailed analysis on wild f i s h . The tanks in these experiments were d e l i b e r a t e l y large and the f i s h well acclimated to c a p t i v i t y in order that they might behave as naturally as possible when expressing their a c t i v i t y . For f i s h in c a p t i v i t y t h i s i s referred to as spontaneous a c t i v i t y , however the term i s somewhat misleading. Fish in nature are also spontaneously active, although i t i s usually i m p l i c i t l y assumed that their behavior i s directed ( i . e . foraging and escape) and that of captive f i s h i s not. Captive f i s h are, however, governed by the same physiological or biochemical systems regulating wild f i s h and therefore l i k e l y to respond as wild f i s h would, within the 77 l i m i t s of t h e i r constraint, given s p e c i f i c s t i m u l i . The infrequent feedings in these experiments were selected to permit completion of SDA in the highest ration treatment before administration of the next meal. This was necessary to define standard metabolism ( i . e . resting post-absorptive metabolism). Sullivan (1982) and Sullivan and Smith (1984) demonstrated that s a b l e f i s h could endure periods up to six months without food and may be adapted to infrequent, large meals. Further, most s a b l e f i s h taken in commercial traps have empty stomachs (McFarlane and Beamish 1983). Consequently, experimental feeding conditions can be considered as not unlike those experienced by wild s a b l e f i s h . Assuming that the s a b l e f i s h in these experiments were responding to endogenous physiological c o n t r o l l i n g mechanisms, the metabolic measurements r e f l e c t the natural energy p a r t i t i o n i n g strategy of wild s a b l e f i s h seeking food. A reduction of a c t i v i t y in response to food deprivation had been observed in a v a r i e t y of organisms. Brown (1946c) reported lethargic behavior of brown trout (Salmo trutta) which had been starved. The routine metabolic rate of brook trout ( S a l v e l l n u s fontinalis) and white suckers (Catostomas commersonii) was observed to decline over short-term starvation more ra p i d l y than standard metabolic rate (Beamish 1964a) i l l u s t r a t i n g a reduction of swimming a c t i v i t y . Dragon f l y larvae reduce a c t i v i t y when in poor feeding environments (Etienne 1972). Callow (1977) describes the reduced of a c t i v i t y in the Turbellarian Dendrocoelum lacteum in response to food deprivation. He reports similar r e s u l t s for the pulmonate gastropod Planozbis contortus 78 (Callow 1974). When starved, the t u r t l e , sternothaerus minor, becomes lethargi c , hardly moving except to breath (Belkin 1965). Although the reduction of a c t i v i t y in response to starvation has been well documented, i t i s of considerable importance that ration and a c t i v i t y metabolism appear to have a dose-response re l a t i o n s h i p (Fig. 2.9). It is d i f f i c u l t to be confident that the form of the curve in F i g . 2.9 i s sigmoid, although the low standard error of the plotted means supports t h i s form. Kerr (1982) suggested t h i s type of r e l a t i o n s h i p with a linear form, however, his work was based on published data collected for d i f f e r e n t purposes with a c t i v i t y estimated by difference and with unknown levels of error (Solomon and B r a f i e l d 1972). This re l a t i o n s h i p indicates that s a b l e f i s h have evolved to conserve energy by minimizing a c t i v i t y when faced with a low p r o b a b i l i t y of prey capture in a poor feeding environment. Sablefish feed on active, motile prey. Reducing a c t i v i t y may also reduce the p r o b a b i l i t y of prey encounter by decreasing the r e l a t i v e v e l o c i t y of prey and predator. Assuming natural selection for energy e f f i c i e n c y and predator and prey movements which are random beyond their respective sensory ranges, a random movement simulation model might demonstrate t h i s . However, i t i s Instructive to know that s a b l e f i s h have evolved to modulate a c t i v i t y in d i r e c t proportion to feeding opportunities. This would suggest that although there may be a reduction in the p r o b a b i l i t y of prey encounter with less a c t i v i t y , i t i s of less significance than the r e s u l t i n g energy saving. This p a r t i t i o n i n g of a c t i v i t y in proportion to food 79 a v a i l a b i l i t y i s done at a constant swimming speed. It can be demonstrated both empirically and with hydrodynamics theory that f i s h have optimal swimming speeds (Brett 1964, 1965, Ware 1975, 1978, Blake 1983). These speeds may d i f f e r depending on the parameter being optimized and arguments have been presented regarding which parameters are optimized (Rosen 1967, Kerr 1971c, Ware 1975), but the existence of optima i s well accepted. The constant swimming speed of s a b l e f i s h , observed in a l l treatments and at any time post-prandial supports t h i s . It means that because s a b l e f i s h regulate their energy expenditure in r e l a t i o n to food supply, they are doing so by regulating their periods of a c t i v i t y . A reduction in swimming v e l o c i t y rather than a c t i v i t y periods has been reported in starved tuna which also prey on contagiously d i s t r i b u t e d , motile prey (Magnuson 1969). However, these f i s h must swim continuously for hydrodynamic and v e n t i l a t o r y reasons (Magnuson 1966) and cannot a l t e r a c t i v i t y periods as can s a b l e f i s h . Longer periods of a c t i v i t y when prey is more abundant and shorter periods when prey i s scarce appears to be the foraging strategy s a b l e f i s h have evolved to optimize some energy parameter, probably growth (Ware 1975). Having recently fed, a sa b l e f i s h can benefit from the expenditure of additional energy seeking prey which may s t i l l be in i t s v i c i n i t y . Sablefish which have not fed for a longer period benefit more from waiting for prey to enter their area than swimming long distances searching for food. Even f i s h near their maintenance r a t i o n , fed only once every two weeks (Table 1.2), are not inactive (Fig. 2.2 and 2.9). Thus, although they appear to be spending a greater proportion of 80 t h e i r time waiting for food, they also probably search the immediate v i c i n i t y should th e i r motile prey be nearby. The standard metabolic rate of f i s h has been used to compare physiological changes in r e l a t i o n to environmental variables. Its d e f i n i t i o n , the energy expenditure of a res t i n g , post-absorptive f i s h , gives l i t t l e information regarding what constitutes the standard metabolic rate, but does provide a means of comparing f i s h experiencing d i f f e r e n t enviromnmental conditions (Fry 1947, 1957, 1971, Brett and Groves 1979). Standard metabolic rate has also been used in ecological models and i s usually assumed to be constant for any given temperature and size of f i s h (Ware 1975, Kerr 1982). When used as a physiological index, i t has been shown that the standard metabolic rate of f i s h changes in response to season (Beamish 1964b, Evans 1984) and starvation (Smith 1935a, b, Beamish 1964a) as well as temperature and weight (Saunders 1963, Beamish 1964c, Beamish and Mookherjii 1964, Brett 1964, 1965, Brett and Glass 1973, Brett and Groves 1979, Edwards et a l . 1972). The apparent rel a t i o n s h i p of standard matabolic rate with rati o n (Fig. 2.10) and days post-prandial (Fig. 2.7) adds further to the evidence that t h i s bioenergetic parameter should only be used in ecological models after c a r e f u l consideration. The Winberg rule, as defined by Mann 1978, and based on the work of Winberg (1956), states that the routine metabolism of f i s h in nature i s roughly twice the standard metabolic rate which in turn is assumed to be constant for a given temperature and f i s h s i z e . C l e arly the standard metabolic rate Is not constant even when 81 temperature and size are incorporated. The r e l a t i v e magnitude of a c t i v i t y metabolism compared to the standard metabolic rate i s low, at least in the captive sa b l e f i s h used here (Fig. 2.9 and 2.10). Similar r e s u l t s have been reported for wild brown trout (Young et a l . 1972) and pike (Esox lucius) (Diana et a l . 1977) on the basis of sonic tagging studies, although no d i r e c t metabolic measurements were made. In the pumpkinseed sunfish, Lepomis glbbosus, the annual energy budget based on laboratory studies consists of 87% standard metabolism and only 13% more for a c t i v i t y metabolism (Evans 1984). The proportion of t o t a l metabolism devoted to a c t i v i t y i s l i k e l y to be a function of the habits of the species examined. Thus, for an active species such as the tuna, Euthynnus a f i n i s , where swimming Is required to maintain hydrostatic equilibrium and provide ram v e n t i l a t i o n (Magnuson 1966, 1969) a c t i v i t y may be far more important in the t o t a l metabolic budget than for ambush predators such as pike or brown trout (Young et a l 1972, Diana et a l . 1977). Sablefish are a c t i v e l y predatory and, in the tanks, swam slowly and s t e a d i l y during the daylight when well fed. Despite t h i s r e l a t i v e l y constant a c t i v i t y , their swimming constituted only a minor f r a c t i o n of their t o t a l metabolic expenditures. Sablefish appear to have evloved e f f i c i e n t foraging behaviors and mechanisms well suited to optimizing returns from an inconsistent food supply. After consuming a large meal, sa b l e f i s h are p o t e n t i a l l y faced with an energy budgeting problem should the combined digestive, a c t i v i t y and standard metabolic loads exceed their aerobic metabolic l i m i t s . Presumably, the costs of standard 82 metabolism are fixed for any given feeding state and cannot change over the short term. Consequently, when digesting and assimilating a meal, sa b l e f i s h can only r e p a r t i t i o n the a c t i v i t y and digestive metabolic demands. It appears that they are capable of d i r e c t i n g t h e i r p h y s i o l o g i c a l l y available oxygen to a c t i v i t y metabolism when necessary (Fig. 3.2). I f , in nature, routine a c t i v i t y levels were high, they would c o n f l i c t with the normal digestion and processing of food. The results of the a c t i v i t y energy expenditure experiments indicate that t h i s i s not the case as routine a c t i v i t y energy expenditure is a small component of the t o t a l energy budget. This lends additional c r e d i b i l i t y to r e l a t i n g the low routine a c t i v i t y energy expenditures observed in the mass respirometers with that of wild f i s h . Further, the regulation of a c t i v i t y by modulating the periods of a c t i v i t y rather than i t s i n t e n s i t y allows periods of quiesence during which digestion can proceed with no competition from swimming a c t i v i t y . Periods of nocturnal i n a c t i v i t y also permit unhindered digestion, although i t i s not known i f wild s a b l e f i s h also display diurnal a c t i v i t y cycles. When the a c t i v i t y and standard metabolic rates of sablefish given d i f f e r e n t feeding opportunities are combined into a routine metabolic rate and expressed as a function of rat i o n (Fig. 2.11) the r e s u l t i n g sigmoid curve assumes a two state appearance. Fish fed every 14 days and starved f i s h have nearly equal routine metabolic rates which are about 25% lower that those of f i s h fed weekly and every four days. This two state system i s paralleled by a similar difference in the energy sources the two groups use 83 to power their metabolic expenditures. Starved f i s h and f i s h fed every two weeks use both exogenous and endogenous l i p i d s as their primary energy source (Fig. 1.5 and 1.6, Table 1.1). Conversely, the two better-fed groups of f i s h catabolize protein almost exclusively to meet the i r energy demands (Fig. 1.7 and 1.8) and r e t a i n the l i p i d s they aquire in their d i e t s . Because their diet contains more than s u f f i c i e n t protein to meet a l l th e i r energy demands, the f i s h fed every four days are also able to retain a portion of th e i r dietary protein. It would not be unreasonable to speculate that s a b l e f i s h fed more frequently than every four days would ret a i n an even greater proportion of their dietary prote i n . The l e v e l of nitrogen excretion i s generally considered to be a d i r e c t function of the rate of nitrogen consumption in f i s h (Gerking 1955, 1971, Birkett 1969, Savitz 1969, 1971). This i s also the pattern observed in s a b l e f i s h i f between-meal nitrogen excretion and ration are expressed on a d a i l y basis (from Table 2.1, ammonia excretion equals: 211 mg/day - 4-day i n t e r v a l , 182 mg/day - 7-day i n t e r v a l , 49 mg/day - 14-day i n t e r v a l ) . The difference between these results and those cited above concerns the nitrogen retention e f f i c i e n c y . On a meal to meal basis, f i s h fed every 14 days retained nitrogen the most e f f i c i e n t l y , f i s h fed every 7 days retained i t least e f f i c i e n t l y , and f i s h fed every fourth days were intermediate between these (Table 2.1). Gerking (1955, 1971) c l e a r l y demonstrated that b l u e g i l l , Lepomis macrochirus, r e t a i n a greater proportion of dietary nitrogen when fed at higher rates. Similar r e s u l t s have been observed in the p l a i c e , sole, and perch (Birkett 1969), and repeated for 84 b l u e g l l l by Savitz (1969, 1971). Gerking (1955) did note a p r e f e r e n t i a l retention of l i p i d s by his f i s h which were a l l fed a high l i p i d d i e t . This agrees with the l i p i d retention observed in well fed s a b l e f i s h . The most s i g n i f i c a n t methodological difference between th i s research and that c i t e d above concerns the means of administering d i f f e r e n t ration l e v e l s . In these experiments the meal size was constant and the i n t e r v a l varied. Gerking, Savitz, and Birkett a l l varied meal size and fed t h e i r f i s h on a d a i l y basis. It is conceivable that the ultimate reason these d i f f e r e n t approaches had d i f f e r e n t e f f e c t s was due to the amino acid pool or nitrogen resevoir (Brody 1945, p. 353). This consists of amino acids and proteins, normally in c i r c u l a t i o n or stored in tissues, which are in dynamic equilibrium with the protein in the diet and functioning proteins in the remainder of the body. As functional proteins become disabled they are replaced by new proteins synthesized from the amino acid pool and subsequently fractionated into amino acids and returned to the pool. When the pool becomes depleted, i t s contents are made up out of dietary protein. Long feeding intervals may deplete these stores r e s u l t i n g in a need to replentish them, whereas regular feeding might provide regular opportunities for amino acid replacement, even at low feeding l e v e l s . This would explain the protein retention e f f i c i e n c y differences i f the longer feeding interval also affected the rate of pool depletion. This could occur when infrequently used enzymes are catabolized between feedings after only a single use, whereas with frequent feeding they may be used 85 more frequently and e f f i c i e n t l y . The proximate reason for the difference in protein retention e f f i c i e n c y in s a b l e f i s h can be found in their use of l i p i d s as metabolic fuel when poorly fed (Table 1.1). The f i s h fed every 4 and 7 days meet metabolic demands with protein catabolism as did the f i s h studied by the other authors. As metabolic demands are r e l a t i v e l y constant, increased ration allows retention of greater amounts of protein giving greater protein conversion e f f i c i e n c y . However, by switching to a l i p i d based metabolism, the s a b l e f i s h fed every two weeks greatly improve their a b i l i t y to r e t a i n protein and presumably their protein reserves. This phenomena may be unique to infrequent feeders such as bathypelagic fishes (Sullivan 1982) or i t may be a resu l t of the ration administration methods used here and common in more fishes. It i s , however, clear that s a b l e f i s h are capable of conserving protein, when necessary, and basing metabolism on l i p i d s . 5.1 SUMMARY: Addressing, the hypotheses posed in chapter 1, from t h i s research the following conclusions can be drawn: 1) The a c t i v i t y metabolism of s a b l e f i s h i s not independent of ration history. A sigmoid function describes the dependence of a c t i v i t y metabolism on ration for captive s a b l e f i s h in large tanks when meal frequency is used to supply d i f f e r e n t levels of rat i o n . 2) The standard metabolic rate of captive s a b l e f i s h i s also a sigmoid function of ra t i o n . The f i s h appear to operate in at 86 least a two state system in which low rations produce consistently low standard metabolic rates while higher rations r e s u l t in up to at least a 25% increase in standard metabolic rate. 3) The feeding metabolism (SDA) of s a b l e f i s h i s r e l a t i v e l y constant regardless of ration history. However, in well fed f i s h the elevation of metabolism from feeding i s more intense and of shorter duration, while in poorly fed s a b l e f i s h the pattern of SDA i s a smaller increase of oxygen consumption over a longer period of time. 4) Feeding metabolism appears to r e s u l t primarily from both l i p i d and protein catabolism with a lesser contribution from protein anabolism. Protein balance i s d i r e c t l y correlated with feeding metabolism, but a high SDA occurs even when protein balance i s extrapolated to zero in the re l a t i o n s h i p , indicating minor importance from protein anabolism. 5) The s a b l e f i s h has physiological mechanisms which allow r e a l l o c a t i o n of metabolism between digestion and locomotion such that both can occur synchronously without exceeding the aerobic metabolic scope. 87 LITERATURE CITED Beamish, F.W.H. 1964a. Infleunce of starvation on standard and routine oxygen consumption. Trans. Am. Fish. Soc. 93:103-107. Beamish, F.W.H. 1964b. Seasonal changes in the standard rate of oxygen consumption on fish e s . Can. J. Zool. 42:189-194. Beamish, F.W.H. 1964c. Respiration of fishes with special emphasis on standard oxygen consumption. I I . Influence of weight and temperature on re s p i r a t i o n of several species. Can. J. Zool. 42:177-188. Beamish, F.W.H. 1970. Oxygen consumption of largemouth bass, Micropterus salmoides, in r e l a t i o n to swimming speed and temperature. Can. J. Zool. 48:1221-1228. Beamish, F.W.H. 1974. Apparent s p e c i f i c dynamic action of largemouth bass, Micropterus salmoides. J. Fish. Res. Bd. Canada 31:1763-1769. Beamish, F.W.H. and P.S. Mookherji. 1964. Respiration of fishes with special emphasis on standard oxygen consumption. I. Influence of weight and temperature on res p i r a t i o n of gold f i s h , Carassius auratus L. Can. J. Zool. 42-161-175. Beamish, F.W.H., A.J. Niimi, and P.F.K.P. Lett. 1975. Bioenergetics of teleost f i s h e s : Environmental influences. In Comparative Physiology - Functional Aspects of Structural Materials. (L. B o l i s , H.P. Maddrell and K. Schmidt-Nielsen eds.). North-Holland Publishing Co., Amsterdam, pp 187-209. Beamish, R.J. and D.E. Chilton. 1982. Preliminary evaluation of a method to determine the age of sa b l e f i s h . Can. J. Fish. Aquat. S c i . 39:277-287. Belkin, D.A. 1965. Reduction of metabolic rate in response to starvation in the t u r t l e Sternothaerus minor. Copeia 1965(3):367-368. Birkett, L. 1969. The nitrogen balance in p l a i c e , sole and perch. J . Exp. B i o l . 50:375-386. Blake, R.W. 1983. Fish Locomotion. Cambridge University Press, Cambridge. 208 p. Blaxter, J.H.S. 1979. The ef f e c t of hydrostatic pressure on fishes. in Environmental Physiology of Fishes (M.A. A l i ed.). Plenum Press, N.Y. pp 369-386. Bligh, E.G. and W.J. Dyer. 1959. A rapid method of t o t a l l i p i d extraction and p u r i f i c a t i o n . Can. J. Biochem. Physiol. 37:911-917. 88 B r a f i e l d , A.E. 1985. Laboratory studies of energy budgets, in Fish Energetics: New Perspectives (P. Tytler and P. Callow eds.). Croom Helm, London. 257-281 pp. Brett, J.R. 1964. The r e s s i r a t o r y metabolism and swimming performance of young sockeye salmon. J. Fish. Res. Bd. Canada 21:1183-1226. Brett, J.R. 1965. The r e l a t i o n of size to rate of oxygen consumption and sustained swimming speed of sockeye salmon {Oncozhynchus nezka). J. Fi s h . Res. Bd. Canada 22:1491-1501. Brett, J.R. 1976. Feeding metabolic rates of young sockeye salmon, Oncorhynchus nezka, in r e l a t i o n to ration l e v e l and temperature. Envt. Canada Fis h . Mar. Serv. Tech. Rept. No.675. 18 p. Brett, J.R. 1979. Environmental factors and growth. in Fish Physiology, Vol. VIII. (W.S. Hoar and D.J. Randall eds.). Academic Press, London, pp 599-675. Brett, J.R. 1985. Correction in use of o x y c a l o r i f i c equivalent. Can. J. Fish . Aquat. S c i . 42:1326-1327. Brett, J.R. and N.R. Glass. 1973. Metabolic rates and c r i t i c a l swimming speeds of sockeye salmon {Oncozhynchus nezka) in r e l a t i o n to size and temperature. J. Fish . Res. Bd. Canada 30:379-387. Brett, J.R. and T.D.D. Groves. 1979. Physiological energetics, in Fish Physiology, Vol VIII. (W.S. Hoar and D.J. Randall eds.). Academic Press, London, pp 279-352. Brody, S. 1945. Bioenergetics and growth. Reinhold, New York. 1923 p. Brown, M.E. 1946a. The growth of brown trout {Salmo t r u t t a Linn.). I. Factors influencing the growth of trout f r y . J. Exptl. B i o l . 22:118-129. Brown, M.E. 1946b. The growth of brown trout {Salmo t r u t t a Linn.). I I . Growth of 2-year-old brown trout at a constant temperature of 11.5 C. J. Exp. B i o l . 22:130-144. Brown, M.E. 1946c. The growth of brown trout {Salmo trutta Linn.). I I I . The e f f e c t of temperature on the growth of two-year-old trout. J. Exptl. B i o l . 22:145-155. Callow, P. 1974. Some observations on locomotory strategies and their metabolic e f f e c t s in two species of freshwater gastropods, Ancylus f l u v i a t u l i s Mull, and Planozbis contoztus Linn. Oecologia 16:149-161. 89 Callow, P. 1977. Ecology, evolution and energetics: a study in metabolic adaptation, in Advances in Ecological Research (A. MacFadyen ed.). Academic Press, London, pp 1-62. Callow, P. 1985. Adaptive aspects of energy a l l o c a t i o n , in Fish Energetics: New Perspectives. (P.Tytler and P. Callow eds.). Croom Helm, London, pp 13-31. Craig, J.F., M.J. Kenley and J.F. T a i l i n g . 1978. Comparative estimations of the energy content of f i s h tissue from bomb calorimetry, wet oxidation, and proximate analysis. Freshw. B i o l . 8:585-590. Davis, G.E. and C E . Warren. 1968. Estimation of food consumption rates. in IBP Handbook No. 3. (W.E. Ricker ed. ). Blackwell S c i e n t i f i c , Oxford, pp 205-225. Dawes, B. 1930. Growth and maintenance in pl a i c e . Part I I I . J. Mar. B i o l . Assn. N.S. 17:877-947. Daxboeck, C. 1981. A study of the cardiovascular system of f i s h (Salmo gairdneri) at rest and during swimming exercise. Ph.D. Thesis, University of B r i t i s h Columbia, Vancouver, B.C. Diana, J.S., W.C. MacKay, and M. Ehrman. 1977. Movements and habitat preference of northern pike (Esox lucius) in Lac Ste. Anne, Alberta. Trans. Am. Fish. Soc. 106-560-565. DuPreez, H.H., W. Strydom and P.E.D. Winter. 1986. Oxygen consumption of two marine te l e o s t s , Lithognathus mormyrus (Linnaeus, 1758) and Lithognathus lithognathus (Cuvier, 1830) ( T e l e o s t i : Sparidae). Comp. Biochem. Physiol. 85a:313-331. Edwards, R.C.C., D.M. Finlayson and J.H.Steele. 1972. An experimental study of the oxgyten consumption, growth, and metabolism of the cod (Gadus morhua L.). J. Exp. Mar. B i o l . Ecol. 8:279-300. Ege, R. and A. Krogh. 1914. On the r e l a t i o n between the temperature and the respiratory exchange in fishes. Int. Rev. Gesamten Hydrobiol. Hydrogr. 1:48-55. E l l i o t t , J.M. 1976. The energetics of feeding, metabolism and growth of brown trout (Salmo t r u t t a L.) in r e l a t i o n to body weight, water temperature and ration s i z e . Anim. Ecol. 45:923-948. E l l i o t t , J.M. 1976. Energy losses in the waste products of brown trout (Salmo t r u t t a L.). J . Anim. Ecol. 45:561-580. E l l i o t t , J.M. 1979. Energetics of freshwater f i s h . Symp. Zool. Soc. Lond. 44:29-61. 90 Etienne, A.S. 1972. The behavior of Aeschna. Anim. Behav. 20:724-731. Evans, D.O. 1984. Temperature independence of the annual cycle of standard metabolism in the pumpkinseed. Trans. Am. Fish. Soc. 113:494-512. Fry, F.E.J. 1947. E f f e c t s of the environment on animal a c t i v i t y . Univ. Toronto Stud. B i o l . Ser. 55:1-62. Fry, F.E.J. 1957. The aquatic r e s p i r a t i o n of f i s h , in Fish Physiology (M.E. Brown ed.). Academic Press, New York, pp. 1-63. Fry, F.E.J. 1971. The e f f e c t of environmental factors on the physiology of f i s h . In Fish Physiology, Vol VI. (W.S. Hoar and D.J. Randall eds.). Academic Press, New York pp 1-98. F u r n e l l , D.J. 1987. P a r t i t i o n i n g of locomotor and feeding metabolism in s a b l e f i s h (Anoplopoma fimbria). Can. J. Zool. 65:486-489. Gerking, S.D. 1955. Influence of rate of feeding on body composition and protein metabolism of b l u e g i l l sunfish. Physiol. Zool. 28:267-282. Gerking, S.D. 1971. Influence of rate of feeding and body weight on protein metabolism of b l u e g i l l sunfish. Physiol. Zool. 44:9-19. Glass, N.R. 1968. The e f f e c t of time of food deprivation on the routine oxygen consumption of largemouth black bass (Micropterus salmoides). Ecology 49:340-343. Hart, J.L. 1973. P a c i f i c Fishes of Canada. B u l l . 180, Fi s h . Res. Bd. Canada 740 p. Haywood, G.P. 1983. Ammonia t o x i c i t y in teleost fishes: a review. Can. Tech. Rept. f i s h . Aquat. S c i . No. 1177. 35 p. Holling, C S . 1959. The components of predation as revealed by a study of small-mammal predation of the European pine sawfly. Can. Entomol. 91:293-320 Hunter, J.R. and G.L. Thomas. 1974. E f f e c t of prey d i s t r i b u t i o n and density on the searching and feeding behavior of l a r v a l anchovy, Engraulis mordax Girard. In, The Early L i f e History of Fish (J.H.S. Blaxter ed.), Springer-Verlag, New York. pp 559-574. Ivlev, V.S. 1939. Energy balance of carps. Zool. Zh. 18:303-318. 91 Ivelv, V.S. 1945. The b i o l o g i c a l production of waters. Usp. Sovrem. B i o l . 19:98-120. (Fish. Res. Bd. Canada Transl. Ser. No. 23: 1727-1759 (1966)). Ivlev, V.S. 1960. On the u t i l i z a t i o n of food by planktophage fis h e s . B u l l . Math. Biophys. 22:371-389. Jones, D.R. 1971. Theoretical analysis of factors Which may l i m i t the maximum oxygen uptake of f i s h : the oxygen cost of the cardiac and branchial pumps. J. Theor.Biol. 32:341-349. Jones, R. 1978. Estimates of the food consumption of haddock (Melanogrammus aeglefinus) and cod (Gadus morhua). J. Cons. i n t . Explor. Mer, 38:18-27. Jobling, M. 1981. The influences of feeding on the metabolic rate of fis h e s : a short review. J. Fish B i o l . 18:385-400. Jobling, M. 1983. Towards an explanation of s p e c i f i c dynamic action (SDA). J. Fish . B i o l . 23:549-554. Jobling, M. 1985. Growth, in Fish Energetics: New Perspectives. (P. Tytler and P. Callow eds.). Croom Helm, London. 213-230 p. Jobling, M. 1980. Effects of feeding on the metabolic rate and the s p e c i f i c dynamic action in pl a i c e , Pleuronectes platessa L. J. Fish . B i o l . 16:629-638. Kelso, J.R.M. 1972. Conversion, maintenance, and assimilation for walleye, Stizostedion vitreum vitreum, as affected by si z e , d i e t , and temperature. J . Fi s h . Res. Bd. Canada 29:1181-1192. Kennedy, W.A. and F.T. Fletcher. 1968. The 1964-65 s a b l e f i s h study. Fi s h . Res. Bd. Canada Tech. Rept. 74. 24 p. Kennedy, W.A. 1969. Sablefish culture a preliminary report. Fish. Res. Bd. Canada Tech. Rept. 107. 20 p. Kennedy, W.A. 1970. Sablefish culture - progress in 1969. Fish. Res. Bd. Canada Tech. Rept. 189. 17 p. Kennedy, W.A. 1971. Sablefish culture - progress in 1970. Fish. Res. Bd. Canada Tech. Rept. 243. 18 p. Kerr, S.R. 1971a. Analysis of laboratory experiments on growth e f f i c i e n c y of fis h e s . J. Fish . Res. Bd. Canada 28:801-808. Kerr, S.R. 1971b. Prediction of f i s h growth e f f i c i e n c y in nature. J. Fi s h . Res. Bd. Canada 28:809-814. 92 Kerr, S.R. 1971c. A simulation model of lake trout growth. J. Fis h . Res. Bd. Canada. 28:815-819. Kerr, S.R. 1982. Estimating the energy budgets of a c t i v e l y predatory fishes. Can. J. Fi s h . Aquat. S c i . 39:371-379. K i t c h e l l , J.F. and D.J. Stewart. 1977. Applications of a bioenergetics model to yellow perch (Pezca flavescens) and walleye (Stizostedion vitreum vitreum). J. Fish. Res. Bd. Canada. 34:1922-1935. Kleiber, M. 1975. The F i r e of L i f e . An Introduction to Animal Energetics. R.E. Krieger Publishing, New York. 453 p. LeBrasseur, R.J. 1969. Growth of juvenile chum salmon {Oncozhynchus keta) under d i f f e r e n t feeding regimes. J. F i s h . Res. Bd. Canada 26:1631-1645. Maciolek, J.A. 1962. Limnological organic analysis by quantitative dichromate oxidation. Res. Rept. U.S. Fish Wildl. Serv. 60:1-61. Mackereth, F.J.H., J. Heron and J.F. T a i l i n g . 1978. Water analysis: some revised methods for limnologists. Freshwater B i o l . Assn. S c i . Pub. No. 36. Magnuson, J.J. 1962. An analysis of aggressive behavior, growth, and competition for food and space in medaka, Oryzias latip e s (Pices, Cyprinodontidae). Can. J. Zool. 40:313-363. Magnuson, J.J. 1966. A comparative study of the function of continuous swimming by scombrid f i s h e s . Proc. P a c i f i c S c i . Congr. 11(7):15. Magnuson, J.J. 1969. Swimming a c t i v i t y of the scombrid f i s h Euthynnus a f f i n i s as related to search for food. FAO Fish. Rept. No. 62(2):439-451. Majkowski, J. and K.G. Waiwood. 1981. A proceedure for evaluating the food biomass consumed by a f i s h population. Can. J. F i s h . Aquat. S c i . 38:1199-1208. Mann, K.H. 1965. Energy transportation from a population of f i s h in the River Thames. J. Anim. Ecol. 34:253-275. Mann, K.H. 1978. Estimating the food consumption of f i s h in nature. in Ecology of Freshwater Fish Production (S.D. Gerking ed. ) . Blackwell, Oxford, pp 250-273. McFarlane, G.A. and R.J. Beamish. 1983. Biology of adult s a b l e f i s h (Anoplopoma fimbria) in waters off western Canada. Proc. 2nd Lowell-Wakefield Fi s h . Symp., Anchorage, Alaska. Alaska Sea Grant Rept. 83-8. 93 Muir, B.S. and C P . Newcombe. 1974. Laboratory observations on f i l t e r feeding in A t a l n t i c mackerel, Scomber scombrus. Mar. Ecol. Lab. Dartmouth N.S. Muir, B.S. and A.J. Niimi. 1972. Oxygen consumption of the euryhaline f i s h aholehole (Kuhlia sandvicensis) with reference to s a l i n i t y , swimming and food consumption. J. Fish. Res. Bd. Canada 29:67-77. Paloheimo, J.E. and L.M. Dickie. 1965. Food and growth of fish e s . I. A growth curve derived from experimental data. J. F i s h . Res. Bd. Canada 22:521-542. Paloheimo, J.E. and L.M. Dickie. 1966a. Food and growth of fishes. I I . Effects of food and temperature on the re l a t i o n between metabolism and body weight. J. Fi s h . Res. Bd. Canada. 23:869-908. Paloheimo, J.E. and L.M. Dickie. 1966b. Food and growth of fish e s . I I I . Relations among food, body size and growth e f f i c i e n c y . J. Fish. Res. Bd. Canada 23:1209-1248. Pandian, T.J. 1967a. Food intake, absorption and conversion in the f i s h Ophlocephalus s t r i a t u s . Helgolander Wiss. Merresuntersuchung 15:637-647. Pandian, T.J. 1967b. Intake, digestion, absorption and conversion of food in the fishes Megalops cyprinoides and Ophiocephalus striatus. Mar. B i o l . 1:16-32. Pentelow, F.T.K. 1939. The rel a t i o n s between growth and food consumption in the browth trout (Salmo t r u t t a ) . J. Exp. B i o l . 16:446-473. Pierce, R.J. and T.E. Wissing. 1974. Energy cost of food u t i l i z a t i o n in the b l u e g i l l (Lepomis macrochirus). Trans. Am. Fish. Soc. 103:38-45. Priede, I.G. 1985. Metabolic scope in fishes, in Fish Energetics: New Perspectives (P. Tytler and P. Callow eds.). Croom Helm. London, pp. 33-64. Pyke, G.H., H.R. Pulliam and E.L. Charnov. 1977. Optimal foraging: a se l e c t i v e review of theory and tes t s . Quart. Rev. B i o l . 52:137-154. Randall, D.J. and C. Daxboeck. 1982. Cardiovascular changes in the rainbow trout (Salmo gairdnerl: Richardson) during exercise. Can. J. Zool. 60:1135-1140. Rosen, R. 1967. Optimality p r i n c i p l e s in biology. Butter-worth and Co., London. 198 p. Rubner, M. 1894. Die quelle der thierischen warme. B i o l . 30:73-142. 94 Rubner, M. 1902. Die Gesetze des Energieverbranchs b e i der Ernahrung. Deuticke, Vienna. Saunders, R.L. 1963. Respiration of the A t l a n t i c cod. J. Fish . Res. Bd. Canada 20:373-386. Savitz, J. 1969. Effects of temperature and body weight on endogenous nitrogen excretion in the b l u e g i l l sunfish (Lepomis macrochizus). J. Fish . Res. Bd. Canada 26:1813-1821. Savitz, J. 1971. Nitrogen excretion and protein consumption in the b l u e g i l l sunfish (Lepomis macrochirus). J. Fish. Res. Bd. Canada 28:449-451. Schoener, T.W. 1971. Theory of feeding strategies. Ann. Rev. Ecol. Syst. 11:369-404. Smith, H.W. 1935. The metabolism of the lungfish. I. General considerations of the fasting metabolism of the active f i s h . J. C e l l u l a r Comp. Physiol. 6:43-67. Smith, H.W. 1935. The metabolism of the lungfish. I I . E f f e c t of feeding meat on the metabolic rate. J. C e l l u l a r Comp. Physiol. 6:335-349. Soofiana, N.M. and A. D. Hawkins. 1982. Energetic costs at di f f e r e n t levels of feeding in juvenile cod, Gadus morhua L. J. Fi s h . B i o l . 21:577-592. Soofiana, N.M. and I.G. Priede. 1985. Aerobic metabolic scope and swimming preformance in juvenile cod Gadus morhua L. J. Fish. B i o l . 26:127-138. Solomon, D.J. and A.E. B r a f i e l d . 1972. The energetics of feeding, metabolism, and growth of perch (Perca f l u v i a t i l i s L.). J. Anim. Ecol. 41:699-718. Stauffer, G.D. 1973. A growth model for salmonids reared in hatchery environments. Ph.D. Thesis, Univ. Washington, Seattle. Strickland, J.D. and T.R. Parsons. 1972. A p r a c t i c a l handbook of seawater analysis. B u l l . F i s h . Res. Bd. Canada 167. 310 p. Sulliv a n , K.M. 1982. The bioenergetics of the sab l e f i s h Anoplopoma fimbria occurring off southern C a l i f o r n i a and energy alocation during low-frequency feeding in deep-l i v i n g benthopelagic fishes. Ph.D. Thesis. University of C a l i f o r n i a , San Diego. 237 p. Sull i v a n , K.M. and K.L. Smith. 1982. Energetics of sa b l e f i s h , Anoplopoma fimbria, under laboratory conditions. Can. J. F i s h . Aquat. S c i . 39:1012-1020. 95 Tandler, A. and F.W.H. Beamish. 1979. Mechanical and biochemical composition of apparent s p e c i f i c dynamic action in largemouth bass, Micropterus salmoides Lancepede. J. Fi s h . B i o l . 14:343-350. Tyler, A.V. and R.S. Dunn. 1976. Ration, growth, and measures of somatic and organ growth in r e l a t i o n to meal frequency in winter flounder, Pseudopleuronectes americanus, with hypotheses regarding population homeostasis. J. Fi s h . Res. Bd. Canada 33:63-75. Vahl, 0. and J. Davenport. 1979. Apparent s p e c i f i c dynamic action of food in the f i s h Blennius pholis. Mar. Ecol. Prog. Ser. 1:109-113. Ware, D.M. 1975. Growth, metabolism, and optimal swimming speed of a pelagic f i s h . J. Fish. Res. Bd. Canada. 32:33-41. Ware, D.M. 1978. Bioenergetics of pelagic f i s h : t h e o r e t i c a l change in swimming speed and ration with body s i z e . J. Fis h . Res. Bd. Canada 35:220-228. Ware, D.M. 1980. Bioenergetics of stock and recruitment. Can. J. F i s h . Aquat. S c i . 37:1012-1024. Warren, C.E. and G.E. Davis. 1967. Laboratory studies on the feeding bioenergetics and growth of fishes. In: The B i o l o g i c a l Basis of Freshwater Fish Production (S.D. Gerking ed.). Blackwell, Oxford, pp 175-214. Weatherly, A.H. 1972. Growth and ecology of f i s h populations. Academic Press. New York. 293 p. Webb, P.W. 1978. P a r t i t i o n i n g of energy into metabolism and growth, in Ecology of Freshwater Fish Production (S.D. Gerking ed.). Blackwell S c i e n t i f i c , London, pp 184-214. Weihs, D. 1974. Energetic advantages of burst swimming. J. Theor. B i o l . 48:215-229. Winberg, G.C. 1956. Rate of metabolism and food requirements of fishes. Beloruss. State Univ. Minsk. (Fish. Res. Bd. Canada Transl. Ser. No. 194 (I960)). Wohlschlag, D.E. 1960. Metabolism of the a n t a r c t i c f i s h and the phenomenon of cold adaptation. Ecology 41:287-292. Young, A.H., P. T y t l e r , F.G.T. Holliday and A. MacFarlane. 1972. A small sonic tag for measurement of locomotor behavior in f i s h . J . F i s h . B i o l . 4:57-65. 96 

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