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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 E F F E C T OF FEEDING FREQUENCY ON THE RESPIRATORY METABOLISM OF SABLEFISH (Anoplopoma fimbria)  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) S c . , The U n i v e r s i t y o f B r i t i s h C o l u m b i a , (1983) A THESIS SUBIMTTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR  THE DEGREE OF  DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE  STUDIES  Department of Z o o l o g y  We a c c e p t t h i s t h e s i s to  the required  as c o n f o r m i n g standard  THE UNIVERSITY OF BRITISH COLUMBIA April Donald  1987  James F u r n e l l , 1987  In  presenting  degree  at  this  the  thesis  in  University of  partial  fulfilment  of  British Columbia, I agree  freely available for reference and study. I further copying  of  department  this or  publication of  thesis for by  his  or  her  representatives.  requirements that the  for  an advanced  Library shall make it  agree that permission for extensive  scholarly purposes may be It  is  granted  by the  understood  that  head of copying  my or  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)  the  ABSTRACT: The of  three components of the a e r o b i c r e s p i r a t o r y  s a b l e f i s h , d i g e s t i o n (SDA), a c t i v i t y , and standard metabolism,  were  examined . s e p a r a t e l y  responding  8.5  - 9.5  4000  and together as  to the independent v a r i a b l e ,  f i s h were s i m i l a r  i n s i z e and  L mass r e s p i r o m e t e r s equipped  14 days.  and  oxygen  activity after  and  with a c t i v i t y meters and  were  consumption, monitored  acclimation  f e e d i n g components of and  protein  respirometer,  energy  activity  compared  were  and  to  ammonia  nitrogen before,  different  feeding  the  was  found are  and  the  metabolism,  catabolism.  before  after  In the  l e v e l s of Imposed  eating  t h a t swimming energy expenditures and  standard  f e e d i n g metabolism.  f u n c t i o n s of  ration  frequency.  r a t e s are a s s o c i a t e d with the greatest  with  the  most  least frequent  meals.  functions  ration history.  based on l i p i d  It  is  The  lowest metabolic  o x i d a t i o n as an energy source.  The  specific  dynamic  direct  rates  fish  p r o t e i n s to meet metabolic needs when on higher a l s o shown t h a t apparent  The  frequent  t o t a l and r o u t i n e metabolic r a t e s are a l s o  of  tunnel  examine  and  and  standard  to  a sigmoid  metabolic  lipid  total  Consequently,  oxidize  in a  continuously  expenditures a t s i m i l a r  r e p a r t i t i o n i n g of locomotor  feedings  both  T h i s permitted e s t i m a t i o n of t o t a l metabolism, the  metabolism,  lowest  F i s h were s t u d i e d i n  of  In  frequencies.  metabolism  All  A f o u r t h s e r i e s of s t a r v e d f i s h served as c o n t r o l s .  and  It  f e e d i n g frequency.  and  excretion,  activity  variables  I d e n t i c a l meals were g i v e n every 4, 7,  mass r e s p i r o m e t e r s ,  during,  dependent  h e l d w i t h i n a temperature range  C on a 12 hr photoperiod.  tunnel r e s p i r o m e t e r .  the  metabolism  are  primarily rations.  action  (SDA)  results  t o a g r e a t e r extent from c a t a b o l i c r a t h e r than  anabolic  processes. When threatens  the d u a l m e t a b o l i c load of locomotion t o exceed  physiological  to  active  component  metabolism  standard  a  single,  history.  whereby  locomotor  i n the mass  oxygen  fish,  supply  is  requirements.  respirometers,  i s generally less  the  than  a  When activity  25%  of the  metabolic r a t e and d i g e s t i o n and locomotion can proceed  synchronously. at  exists  shunted  spontaneously of  digestion  the a e r o b i c metabolic scope of the  mechanism  preferentially  and  When swimming spontaneously, probably optimal v e l o c i t y  the s a b l e f i s h move  regardless  The b e t t e r f e d f i s h i n the experiments  of  ration  were a c t i v e most  of the day d e s p i t e the low c o n t r i b u t i o n of the a c t i v i t y component to the r o u t i n e metabolic  rate.  These r e s u l t s have s i g n i f i c a n c e r e g a r d i n g assumptions made  i n b i o e n e r g e t i c models,  expenditures ration.  They  and  s p e c i f i c a l l y that a c t i v i t y  standard metabolic r a t e s a r e  reveal  an  adaptable  physiology  energy  independent  of  which  applies  the  changing  different  energy  metabolic  needs of f i s h i n a dynamic environment with a v a r i a b l e  food supply.  p a r t i t i o n i n g s t r a t e g i e s t o meet  often  TABLE OF CONTENTS: Contents  Page  Abstract  ii  L i s t of Tables  vi  L i s t of F i g u r e s . . .  v i i  Acknowledgements  ix  Chapter 1: General I n t r o d u c t i o n and Methods  1  1.0 I n t r o d u c t i o n  1  1.1 Feeding Metabolism  5  1.2 A c t i v i t y Metabolism  7  1.3 Standard M e t a b o l i c  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 N u t r i e n t P a r t i t i o n i n g S t r a t e g y and Feeding Metabolism (SDA) of s a b l e f i s h  15  2.0 I n t r o d u c t i o n  15  2.1 Methods  16  2.2 R e s u l t s  20  2.3 D i s c u s s i o n  31  Chapter 3: The E f f e c t of Ration  on the A c t i v i t y and  Standard Metabolism of S a b l e f i s h  39  3.0 I n t r o d u c t i o n  39  3.1 Methods  41  3.2 R e s u l t s  45  3.3 D i s c u s s i o n  61  iv  Chapter  4: P a r t i t i o n i n g of Locomotor and Metabolism 4.0  Chapter  66 66  4.1 Methods  67  4.2  Results  70  4.3  Discussion  74  5: General D i s c u s s i o n  77  5.0 6.0  Introduction  Feeding  Summary  86  Literature Cited  88  v  LIST OF TABLES: Table  Page  2.1  Energy, p r o t e i n and l i p i d budgets f o r s a b l e f i s h d i f f e r e n t feeding i n t e r v a l s  2.2  Estimates of SDA f o r s a b l e f i s h with d i f f e r e n t intervals  3.1  D e f i n i t i o n of pre and p o s t - a c c l i m a t i o n  3.2  Between meal d a i l y a c t i v i t y f o r s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s 56  vi  with  feeding  feedings  33 37 47  LIST OF FIGURES: F i g u r e Number  Title  Page  2.1 Oxygen consumption of s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s  21  2.2 Oxygen consumption and ammonia n i t r o g e n e x c r e t i o n of s a b l e f i s h d u r i n g a c c l i m a t i o n t o weekly meals  22  2.3 Oxygen consumption and ammonia n i t r o g e n e x c r e t i o n of s a b l e f i s h d u r i n g a c c l i m a t i o n t o meals every 4 days....23 2.4 Ammonia n i t r o g e n e x c r e t i o n of s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s  25  2.5 T o t a l and p r o t i e n dependent energy expenditures s a b l e f i s h during starvation  27  of  2.6 T o t a l and p r o t e i n dependent energy expenditures of s a b l e f i s h a f t e r a c c l i m a t i o n t o meals every 14 days....28 2.7 T o t a l and p r o t e i n dependent energy expenditures of s a b l e f i s h a f t e r a c c l i m a t i o n t o meals every 7 days 2.8 T o t a l and p r o t e i n dependent energy expenditures  29  of  s a b l e f i s h a f t e r a c c l i m a t i o n t o meals every 4 days 3.1 The a c t i v i t y meter  30 43  3.2 D a i l y a c t i v i t y counts f o r s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s 3.3 T o t a l metabolism of s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s  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 a c c l i m a t e d t o 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 a c c l i m a t e d t o 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 a c c l i m a t e d t o meals every 14 days  52  3.7 Standard and d i g e s t i v e metabolism of s a 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  54  3.8 A c t i v i t y metabolism of s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s  55  46  3.9 R e l a t i o n s h i p between a c t i v i t y metabolism and r a t i o n i n s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s . . . 57  vii  3.10  R e l a t i o n s h i p between standard metabolism and r a t i o n i n s a b l e f i s h a c c l i m a t e d to d i f f e r e n t f e e d i n g i n t e r v a l s  3.11 R e l a t i o n s h i p between r o u t i n e metabolism and r a t i o n i n s a b l e f i s h a c c l i m a t e d t o d i f f e r e n t feeding i n t e r v a l s  59 60  4.1  Oxygen consumption of s a b l e f i s h i n a 4000 L mass respirometer a f t e r a c c l i m a t i o n t o weekly meals  71  4.2  Oxygen consumption of s a b l e f i s h before and a f t e r feeding  73  viii  i n a tunnel  respirometer  ACKNOWLEDGEMENTS: Many this The  research  i n several organizations  contributed  and t h e i r a s s i s t a n c e i s g r e a t f u l l y  B r i t i s h Columbia Science C o u n c i l provided  to  acknowledged.  personal  support  Technology  Award.  N a t u r a l Sciences and E n g i n e e r i n g Research C o u n c i l of  Canada  with The  individuals  a  Graduate Research i n E n g i n e e r i n g and  provided  an  NSERC  Post-graduate  expenses  and equipment  Scholarship.  A l l research  were s u p p l i e d by the Canadian Department  of F i s h e r i e s and Oceans, P a c i f i c B i o l o g i c a l S t a t i o n . Academic Brett.  and  moral support  was given f r e e l y  by  H i s i n s i g h t s and enthusiasm were i n v a l u a b l e .  Dr. J.R. Drs. D.J.  R a n d a l l and A.V. T y l e r provided c r i t i c a l a p p r a i s a l of manuscripts and a d m i n i s t r a t i v e 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 S t a t i o n i n Nanaimo, B.C. and the s t a f f was of  great a s s i s t a n c e ,  White, H.  specifically,  G.A.  McFarlane,  Dr. C.C. Wood, Dr. C. C l a r k e , J . Blackburn,  Kreiberg,  W. Shaw, and M. Smith.  The remaining  Dr. Ian  J . Shelbourn, r e s e a r c h was  perfomed a t the Bamfield Marine S t a t i o n with a s s i s t a n c e from  Dr.  R. Foreman and J . G l a z i e r . For t h e i r p a t i e n c e and perserverence inconvenient  hours,  i n the face of long and  I a l s o 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 a r e r e f e r e d t o as  bioenergetics  (Beamish e t a l .  ( B r e t t and Groves 1979). i n homeotherms, Brody  (1945)  1975) or p h y s i o l o g i c a l e n e r g e t i c s  Rubner (1894, 1902) pioneered  the h i s t o r y of which i s e x t e n s i v e l y reviewed and  Kleiber  (1975).  The  foundation  b i o e n e r g e t i c s can be a t t r i b u t e d t o I v l e v (1939, earlier  publications  on the t o p i c appear  Dawes 1930, Pentlow 1939). as  fish  such work  culture  1945),  (Ege and  and a  theoretical  fish  although  Krogh  E n e r g e t i c s r e s e a r c h gained  developed  of  by  1914,  importance  background  for  understanding the r e l a t i o n s h i p s between feeding and growth became necessary. the  Concurrently,  management of w i l d f i s h stocks  1966b,  Kelso  1971a,  b,  studying adopt  1972,  c,  1982).  These  1966a,  Ware 1980,  of  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  rather  models.  The  fishery  management l i e s  is  than the more  difficulty  in  using  traditional  single  bioenergetics  for  i n t r a n s f e r r i n g l a b o r a t o r y estimates  parameters t o f i s h  activity  c o n t r i b u t i o n s provide  Kerr  a means  multi-species,  metabolic  (Paloheimo and D i c k i e  K i t c h e l l and Stewart 1977,  species  how  bioenergetics research contributed to  i n nature,  of  e s p e c i a l l y understanding  r e g u l a t e d and i t s importance i n  energy  flow.  T h i s r e s e a r c h addresses the r e g u l a t o r y r o l e t h a t r a t i o n may over  aspects  respiratory standard  of  the three g e n e r a l l y recognized  metabolism:  1)  activity,  or maintenance metabolism.  2)  to the i n t e r a c t i o n of the v a r i a b l e s d i g e s t i o n and  1  components  digestion,  Consideration  play  and  i s also activity,  of 3)  given and  the  energy sources used to power metabolism. The t h e o r e t i c a l  built  framework upon which b i o e n e r g e t i c models are  i s the balanced energy e q u a t i o n ,  form depending on a n l y t i c a l o b j e c t i v e s Warren  and  Davis 1967,  Groves  1979,  i n a more or l e s s ( I v l e v 1945, Winberg  Weatherly 1972,  Calow 1985).  complex  Webb 1978,  1956,  Brett  I t s e r v e s as an a c c o u n t i n g  of a l l  energy inputs and e x p e n d i t u r e s experienced by an organism, being  equated by the f i r s t  law of thermodynamics  constant heats ( K l e i b e r 1975). have  u n i t s of energy/time,  meal to meal b a s i s . International  and  these  and the law  The equation's v a r i a b l e s  of  usually  although they can be expressed on  a  The symbols and d e f i n i t i o n s below f o l l o w the  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 m a t e r i a l s excreted or  through the g i l l s  and  i n the  urine  skin  dB = T o t a l change i n energy value of body (growth) i n c l u d i n g both somatic and  materials reproductive  tissues Rs = Energy r e l e a s e d by the metabolism of unfed, resting fish Rd  (standard  metabolism)  = Energy r e l e a s e d d u r i n g assimilation,  storage,  consumption, and  digestion,  catabolism  m a t e r i a l s consumed Ra = Energy r e l e a s e d  i n swimming and other a c t i v i t y  2  of  Because metabolism v a r i e s with s i z e , the parameters are expressed  relative  to  weight  resulting  units  of  s p e c i f i c a l l y fishes,  the  energy/weight/time.  In heterotherms,  time  relationship  can  factors  (Fry  1947,  1971,  Body  size  and  scale  of  controlling temperature.  the  important v a r i a b l e s , relationship.  be  in  altered Brett  temperature  This has been demonstrated  are  the  such two  most  implies  that any experimental i n v e s t i g a t i o n must be designed  Within  the  representing Most  fish  for variations equation,  the input can  live,  Elliott  regression  (Wohlschlag  or c o n t r o l  i n body s i z e and  ration  is  a  temperature. factor  grow and reproduce over a wide  range  i n the equation depend on r a t i o n  extensively  to  organism.  hand  most  and  of environmental energy to the  however, the p r o p o r t i o n s  The  1976a)  limiting  ration levels, variables  as  i n f l u e n c i n g the  by m u l t i p l e  1973,  abiotic  anlysis  include  Stauffer  by  1979)  e x t r i n s i c to the e q u a t i o n ,  1960,  generally  studied  of  and magnitudes of r i g h t (Priede  1985).  i n t e r a c t i o n of r a t i o n with  right-  hand v a r i a b l e s concerns growth r a t e s and c o n v e r s i o n e f f i c i e n c i e s . Paloheimo general  and  Dickie  (1965) used the energy  equation  in  more  form. pR = T + dW  / dt  (2)  Where: R = R a t i o n p = Proportion equivalent T = Total  of r a t i o n  t o 1-((F+U)/C) (eq. 1)  metabolism;  equivalent dW  assimilated;  to Rd+Rs+Ra  (eq.l)  = Change i n weight or c a l o r i e s (dB i n eq. 1)  dt = Change i n time 3  They  express c o n v e r s i o n e f f i c i e n c y as I v l e v ' s (1945) f i r s t  order  term ( K l ) . -a K l = dW  -bR  / Rdt = e  (3)  Where: a and b are c o n s t a n t s Reviewing  f i s h growth l i t e r a t u r e ,  these authors  conclude  c o n v e r s i o n e f f i c i e n c y i s a d e c r e a s i n g f u n c t i o n of r a t i o n , linear  form  on a l o g a r i t h m i c p l o t as i n d i c a t e d by the  slope of the f a r r i g h t hand term slope  i n the e x p r e s s i o n .  simplified widely  energy  accepted  (Fry 1947,  equation  (eq.  2) which they  weight-power f u n c t i o n f o r  having negative  The  r e s u l t s from an i n c r e a s e i n the metabolic term  that  negative  (T) of  equate  standard  the  to  the  metabolism  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 a l l ranges  t h a t the exponent,  of weight,  b,  r a t i o n , and  t h a t changes i n the c o e f f i c i e n t , decrease  in  i s r e l a t i v e l y constant  over  l e v e l of metabolic a c t i v i t y a,  account  K l with i n c r e a s e d r a t i o n .  and  f o r the l o g a r i t h m i c  They do  not,  however,  s p e c u l a t e on the form of the r e l a t i o n s h i p between 'a' and  ration  because they lack d a t a . In and and  D i c k i e may  levels.  the r e l a t i o n s h i p proposed  be true (Labrasseur 1969,  i n many s p e c i e s  ration (T,  g e n e r a l terms,  a decrease  Paloheimo  Kerr 1971a, 1971b,  i n K l has been observed  at  1982) high  T h i s i s a t t r i b u t e d to e l e v a t e d t o t a l metabolism  equation 4) which i s e q u i v a l e n t to the sum  i n equation 1.  by  of Rs, Rd, and  I t i s t h e r e f o r e of both t h e o r e t i c a l and 4  Ra  practical  Interest  to  understand  the  relationship  between  the  metabolic subcomponents and the l e v e l of r a t i o n i n t a k e . because rate  important  to observe  conditions  metabolic 1.1  Further,  the l e v e l of t o t a l a e r o b i c metabolism i s l i m i t e d by  of oxygen uptake (Jones 1971,  normal  three  how  B r e t t and Groves 1979)  i t is  these subcomponents i n t e r a c t both  and when they t h r e a t e n to exceed  the  under aerobic  scope.  FEEDING METABOLISM, Rd: Feeding  metabolism,  encompasses  the  as  energy  used  expended  in  this  presentation,  capturing,  absorbing,  a s s i m i l a t i n g and c a t a b o l i z i n g food e x c l u s i v e of concurrent expenditures on swimming and standard metabolism. termed t h i s the apparent this as  the  i s observed increased  s p e c i f i c dynamic a c t i o n  of the e f f e c t appears  q u a l i t y and q u a n t i t y , rise  in  excitment  the  i n g e s t i n g food. expenditures little  to be a d i r e c t  immediately  mechanical  energy  fish,  measured and  The magnitude and f u n c t i o n of r a t i o n The  after eating, expended  is  initial due  to  obtaining  and  Tandler and Beamish (1979) have documented these  s e p a r a t e l y and  significance  expenditures.  In  feeding  in s i m i l a r l y acclimated f i s h .  metabolic r a t e , and  (SDA).  c o i n c i d e n t with  continuing for a s i g n i f i c a n t period afterward. duration  Beamish (1974)  as an e l e v a t i o n of energy expenditure,  oxygen consumption,  energy  By  found the mechanical  compared  giving  with  fish  the  c o s t s to be  overall  iso-caloric diets  of  of  feeding different  volume, estimates can a l s o be made of the energy expenditure made on  gut mechanics which are a g a i n not thought  to be  significant.  The c o s t of enzyme manufacture, d i g e s t i o n , and a b s o r p t i o n of food  5  from  the gut  separated costs  into c i r c u l a t i o n  i s not w e l l known nor has  from the c o s t s of c e l l u l a r  of  r e t a i n i n g metabolites  regarding  the  specifically  sources  of  as t i s s u e .  SDA  whether i t i s due  metabolite  it  been  c a t a l y s i s or  Controversy  subsequent  to  the  exists  absorption,  to c a t a b o l i c or a n a b o l i c  processes  or both. Traditionally,  SDA  was  thought to o r i g i n a t e p r i m a r i l y from  deamination of amino a c i d s i n the from  carbohydrate and  1975,  B r e t t and  associated 1981,  1985).  irreconcilable  differences  The  those  consumed.  If one maintain  fundamental  the way  comes  from  the  seemingly  metabolism  observation  the  state  utilization.  question  affects It  arises  is  of  structural  of  anabolic  integrity  of  how  the s t r a t e g y of  of n u t r i e n t s may and  to 6  a  SDA.  well  ration the  to from  current (i.e.  the  f a t e of  feeding absorbed  require a d i f f e r e n t  c a t a b o l i c processes  compared  catabolism  metabolite  s t a t e or r e c e n t r a t i o n h i s t o r y of a f i s h on the  partitioning  being  systems attempting  i s important to c o n s i d e r  A f i s h deprived  maximum  maximum growth  or the other as the primary cause of  d e s p i t e a v a r i a b l e supply  is that  maximum growth a l s o d i s p l a y the  the c o n d i t i o n s which support  homeostasis  nutrients.  (Jobling  and  feeding  views f i s h as dynamic chemical  physiological  Kleiber  i n which the g r e a t e s t amount of food  environment,  energy)  1974,  Thus i t i s d i f f i c u l t to decouple growth and  to i d e n t i f y one  the  are  in  contention  Unfortunately, also  (Beamish  More r e c e n t l y , some authors have  These  c o n d i t i o n s which support  are  lesser contributions  with the a n a b o l i c d e p o s i t i o n of t i s s u e  1983,  SDA.  catabolism  Groves 1979).  SDA  viewed.  lipid  l i v e r with  fed  to  maintain  fish.  The  controversy  surrounding  metabolism  may  be  approached  comparing the metabolic catabolism  (i.e.  the cause of apparent using  this  SDA  or  feeding  perspective.  response as w e l l as the l e v e l of  nitrogen  excretion)  shown  by  By  protein  fish  given  i d e n t i c a l meals a f t e r e x p e r i e n c i n g d i f f e r e n t r a t i o n h i s t o r i e s which  p a r t i t i o n i n g of anabolism  some understanding 1.2  c a t a b o l i s m may  of the cause of SDA  may  be  different,  be p o s s i b l e .  ACTIVITY METABOLISM, Ra: The  will  term a c t i v i t y metabolism,  refer  concurrent  standard  energetic  hypothetically  have only been  (Kerr 1971b,  c,  1982)  Kerr's  v a r i a b l e s by  of r a t i o n .  metabolic  dealt  with  with  components  data.  difference  e r r o r s i n the remainders (Solomon r e s u l t s suggest  of  e x c l u s i v e of the  d i f f e r e n c e from p u b l i s h e d growth  of  differences  The  i n r e l a t i o n to r a t i o n ,  equation  exclusive  p o s s i b l e SDA.  of food d i g e s t i o n ,  energy  compounding  function  Ra,  for f i s h  by  estimating  1972),  metabolism and  Rs and costs  estimated  as used i n t h i s p r e s e n t a t i o n ,  to the energy a f i s h expends swimming  components,  and  and  in  and  Although leads  to  Brafield  t h a t f o r a g i n g a c t i v i t y may  be  a  T h i s r a i s e s the q u e s t i o n of whether r a t i o n  cause a c t i v i t y d i f f e r e n c e s and  i f so what  the  form  magnitude of the r e l a t i o n s h i p i s . Active  important pelagic  swimming energy  species  while  expenditure (Kerr  r e p r o d u c t i v e behavior,  foraging of  1982).  is  predatory Other  t e r r i t o r y defense,  escape  from  level,  e s p e c i a l l y i n sedentary  probably fishes,  social  7  most  especially  activities  p r e d a t i o n a l s o c o n t r i b u t e to the territorial  the  such  as  i n t e r a c t i o n , or  active  fishes.  metabolic  However, f o r  p e l a g i c , predatory  s p e c i e s , t h e i r magnitude, i n the  not of great s i g n i f i c a n c e (Schoener 1971, 1982).  A change i n a c t i v i t y has  duration.  A  a c t i v e over  f i s h may  periods  (1975,  which  f o r a g i n g speed.  discusses  difficult  to  fishes. could  apply  changes mackerel Thomas  of  swimming  c r u i s i n g speed  and gives  Although c o n c e p t u a l l y  distinct,  naturally  it  is  occurring  f o r prey when hungry; hence, f o r a g i n g speed long d i s t a n c e s  or c r u i s i n g  while  c o n t a g i o u s l y d i s t r i b u t e d prey.  prey  response  advantages  suggests there are two  Optimal f o r a g i n g speed i s thought to i n c r e a s e with  and  l a t t e r the g r e a t e s t c a l o r i c r e t u r n , at  apply to f i s h t r a v e l l i n g  seeking  the s e l e c t i v e  these d i s t i n c t i o n s to  F i s h search  be  both.  For each u n i t of energy spent, the former  given prey d e n s i t y .  and  swimming speed and  be s e l e c t i v e l y optimized,  the g r e a t e s t d i s t a n c e , the a  intensity  of a c t i v i t y , or i t can do  1978)  may  components;  Kerr  i t can a l t e r swimming speed  swimming at d i f f e r e n t speeds and speeds  Pyke et a l . 1977,  a constant  d i f f e r e n t periods,  r e t a i n constant Ware  maintain  two  long term, i s  density  (Ware 1975,  ( H o l l i n g 1959). in  1978)  Further  in a  typical  1974).  Newcombe 1974)  This  functional  evidence t h a t f o r a g i n g  response to prey d e n s i t y i s found  (Muir and  asymptotically  and  in  the  anchovy l a r v a e  suggests t h a t i t may  be a  speed  Atlantic  (Hunter  change  in  and the  i n t e n s i t y component of f o r a g i n g r a t h e r than d u r a t i o n which causes the  increase  i n the a c t i v i t y component of metabolism at  ration levels. distributed  These o b s e r v a t i o n s  prey.  It  is  are,  possible  however, that  environment with c o n t a g i o u s l y d i s t r i b u t e d ,  8  a  for  predator  higher  uniformly in  an  m o t i l e prey would  do  well and  to i n c r e a s e the time spent s e a r c h i n g had prey were i n i t s v i c i n i t y ,  and  reduce search time  starvation.  By  and  i t when prey were s c a r c e ,  reducing  i t r e c e n t l y eaten,  i n c r e a s i n g search time when prey were  density.  reduced  Evidence  t h i s comes  ration  B e l k i n 1965,  Glass 1968).  a c c l i m a t i z a t i o n may  serve as a  optimize f o r a g i n g a c t i v i t y energy  of  observations  of  a c t i v i t y can be d i v i d e d i n t o two and e a t i n g prey,  and  Recent r a t i o n cueing  history  mechanism  i t i s apparent  that  a r e a s : 1) energy spent c a p t u r i n g  The  be r e l a t e d to immediate and  long term  extent to which r a t i o n r e l a t e d changes  efficiency Dickie  at  (1966a),  responding data  They  proper with  and  provide  f o r other purposes.  f i s h with a  by  Consequently,  of  they  kowledge of r e s u l t i n g e r r o r magnitudes  ration  l e v e l s on a c t i v i t y and  total  conversion  Paloheimo  means  The  metabolism.  devoted  both  4)  and  optimally The  only  are  been  without  r e q u i r e a p p l i c a t i o n of u n c e r t a i n assumptions  1966a).  energy  observed  in  a v a i l a b l e to examine t h i s p o s s i b i l i t y have  Dickie  of  f o r the d e c l i n e  high r a t i o n l e v e l s ,  c o n t r o l s and no  account  to changes i n prey d e n s i t y and d i s t r i b u t i o n .  currently  collected  may  in  eq.  1  unknown.  to  foraging  a c t i v i t y c o n t r i b u t e to the l e v e l of t o t a l metabolism ('a , is  1962,  2) energy spent p o s t - f e e d i n g when s e a r c h i n g  for prey, both of which may history.  Magnuson  expenditures.  From the f o r e g o i n g d i s c u s s i o n ,  ration  from  operate  regardless  a c t i v i t y d u r i n g s t a r v a t i o n (Brown 1946a,  Beamish 1964a, or  of  abundant  a predator might  more e f f i c i e n t l y than by making equal expenditures prey  following  present r e s e a r c h examines  (Paloheimo the  effect  t h e i r combined e f f e c t on the  T h i s should provide i n f o r m a t i o n to s e a r c h i n g f o r and 9  consuming  and of  level  on  the  prey  and  establish  i f these expenditures are r e l a t e d to e i t h e r long  term  or immediate r a t i o n h i s t o r y . 1.3  STANDARD METABOLIC RATE, Standard  metabolism i s d e f i n e d  a r e s t i n g , post-absorptive assumed  to  measured  be in  constituted also  constant  as the energy expenditure of  f i s h a t a s p e c i f i e d temperature. I t i s i n any  post-absorptive  feeding fish.  the sum  r a t e under  a  different  or  is  it  associated  with n e u r a l  in  on s u b s t r a t e  part,  ration  history  may  standard  definition specific has  the  acetylcholine  of standard  standard  but not  For  esterase  in  muscle  metabolic  rate  Many r e a c t i o n r a t e s depend,  concentration.  Immediate and  concentration  such as amino a c i d s and  metabolic r a t e .  long  of  routinely  hence, may  Much of the problem l i e s  affect in  the  describing  energy-consuming f u n c t i o n s the contemporary  definition  has  measurements  little  metabolic r a t e .  term  Rather than  Relatively  but  l i m i t e d p r e d i c t i v e value.  work has  on the standard of  been done on the e f f e c t s  metabolic r a t e  metabolism are u s u a l l y not  with a c t i v i t y m o n i t o r i n g . activity  of  i n f l u e n c e the  comparative v a l u e ,  history  part  functioning?  c i r c u l a t i n g metabolites the  and  is  difficulty  conditions.  locomotor c o s t of the nervous work done  contraction  rate  reactions  T h i s leads to  example, i s the cost of a c e t y l c h o l i n e synthesis  only  r e s p i r a t o r y mechanics,  or locomotion.  the standard  although  standard  of a l l endothermic enzyme  with feeding  predicting  state, The  i n p a r t by c i r c u l a t o r y and  includes  associated  Rs:  metabolism  from  of  fishes  made  It i s therefore d i f f i c u l t total 10  metabolism  to  ration because  synchronously to  eliminate  estimate  Rs.  Further, this  standard metabolic r a t e ,  component  regardless  of  examination (1964a) white  of  total  as normally d e f i n e d ,  energy  expenditure  the f i s h e s ' c o n d i t i o n and  is  therefore  assumes constant,  requires  beyond documentation at the d e f i n e d l e v e l .  reports  a  suckers  decrease  (Catastomus  Beamish  i n the standard metabolic commezsonii)  and  rate  brook  ( S a l v e l i n u s f o n t i n a l i s ) with s t a r v a t i o n over two days. no  work  d e a l i n g with a dose-response  standard  metabolic  consideration  discussed  surprising. fish  rate,  curve between  although  given  research  ration  the  and  enzymatic  therefore  be  on e n e r g e t i c s modeling  dependent o n l y on temperature  metabolic r a t e ,  trout  above such a r e l a t i o n s h i p would not  T h i s would have an impact  will  of  There i s  p o p u l a t i o n s where the standard metabolic r a t e i s  considered  no  and  body  examine the response  of  as normally d e f i n e d and measured,  of  generally  mass. the  This  standard  to  different  l e v e l s of food consumption and the p r o p o r t i o n of t o t a l  metabolism  i t represents. 1.4  SUMMARY: The  upon Rs,  following presentation  examines the impact  the three r e c o g n i z e d components of r e s p i r a t o r y Rd,  and  Ra.  T h i s w i l l provide i n s i g h t s i n t o  ration  metabolism, the  p a r t i t i o n i n g s t r a t e g i e s s a b l e f i s h use when i n t e r a c t i n g with environment  and  i t s v a r i a b l e food s u p p l y .  Specific  has  energy their  hypotheses  are: 1) A c t i v i t y metabolism i s independent 2) Standard ration  metabolism,  of r a t i o n  as c u r r e n t l y d e f i n e d ,  history. 11  history. i s independent  of  3)  Feeding  metabolism,  resulting  independent of r a t i o n 4) Feeding  from  identical  meals,  history.  metabolism i s a r e s u l t of both a n a b o l i c and  processes  which can be  5) Changing metabolic  is  catabolic  separated.  demands can r e p a r t i t i o n energy s u p p l y among  the r e s p i r a t o r y metabolic  components.  These questions w i l l be addressed  i n separate  chapters w r i t t e n as  independent s t u d i e s with a preceding general methods s e c t i o n  and  d i s c u s s e d as a whole i n a f i n a l g e n e r a l d i s c u s s i o n . 1.5  THE  STUDY SPECIES:  The 1973), found  s a b l e f i s h or blackcod, was  chosen f o r experiments.  It i s a bathypelagic  o f f the north e a s t e r n P a c i f i c c o a s t .  abundantly  near  sablefish depth.  is  700m  easily  Because  importance and  Anoplopoma f i m b r i a P a l l a s (Hart  it  intensively  managed.  include  taken a l i v e is  Kennedy 1969,  swim  of  1970,  from  considerable  1) hardiness  (Beamish and  C h i l t o n 1982),  i n the  the great  commercial  domestication 1971),  most  bladder,  (Kennedy  sablefish  Advantages of t h i s s p e c i e s as a  Smith 1982),  pers.  a  occur  i n good c o n d i t i o n  a species  S u l l i v a n and  amenable  Lacking  with e x c e l l e n t p o t e n t i a l f o r  F l e t c h e r 1968,  subject  depth.  Adults  fish  are  research  laboratory (Sullivan  2) the l a r g e range of s i z e s 3) i t s h a b i t of slow steady  1982,  available swimming  to t u n n e l r e s p i r o m e t r y with low v a r i a n c e r e s u l t s  (Brett  comm.), 4) r e s i s t a n c e to d i s t u r b a n c e s , 5) t o l e r a n c e of  oxygen  c o n c e n t r a t i o n s t y p i c a l of b a t h y p e l a g i c  1979),  and  species  (Blaxter  6) ready acceptance of a great v a r i e t y of foods  in c a p t i v i t y .  A l l f i s h used i n t h i s study were approximately 12  low  while one  kg i n weight and s e x u a l l y immature. on  its  availability  equipment. least  All  suitability  to  s e l e c t e d based  the  experimental for  at  s i x months p r i o r to experiments and a c c l i m a t e d t o a 12  hr  photoperiod per  and  T h i s s i z e was  s a b l e f i s h used were held i n c a p t i v i t y  a t 8° - 9° C.  They were fed 50 g of chopped  f i s h weekly with o c c a s i o n a l 50 g meals of squid  herring  i n place  of  herr i n g . 1.6 GENERAL METHODS: Estimating analysis.  energy equation v a r i a b l e s r e q u i r e s  These  experiments  employed  two  calorimetric  types  calorimetry  to  measure  m e t a b o l i c energy and  calorimetry  to  estimate the energy of food given  of  direct to  indirect oxidative sablefish  d u r i n g the experiments. Indirect organism,  c a l o r i m e t e r s monitor the oxygen consumption  which  can  be  converted to the  applying o x y c a l o r i f i c equivalents 1985).  The  living  oxygen  Pierce  W i s s i n g 1974).  (Saunders 1963,  Solomom and  Each  mechano-electric synchronously  1979,  Brett mass  consumption  Brafield  activity,  and  from  digestive  mass r e s p i r o m e t e r was a l s o equipped with activity  with  meters  respiratory  to  record  fish  measurements.  from 1972,  The c a l c u l a t e d energy r e l e a s e  a system i s the sum of standard,  metabolism.  by  i n l a r g e c o n t a i n e r s while i s o l a t e d  atmospheric  such  released  T h i s c o n t i n u o u s l y measures the oxygen  groups of f i s h  and  ( B r e t t and Groves  an  primary i n d i r e c t c a l o r i m e t r i c method used was  respirometry. of  energy  of  two  activity Two  mass  r e s p i r o m e t e r s were used with groups of 5 u n i f o r m s i z e f i s h having approximately  5  kg  total  biomass a c c l i m a t e d 13  to  four  ration  levels.  Details  of r e s p i r o m e t e r o p e r a t i o n are provided i n the  methods s e c t i o n s of the f o l l o w i n g c h a p t e r s . The 1.5  m  mass r e s p i r o m e t e r s c o n s i s t e d of l a r g e o v a l deep  and  4000 L volume) f i b e r g l a s s  tanks  t r a n s l u c e n t , f l o a t i n g PVC b l a n k e t s which extended water s u r f a c e and excluded atmospheric oxygen. constructed  from  plastic  bubbles  between two 0.4 mm sheets of PVC. use,  heat exchangers  blankets  to  of 8.5°+0.5°C.  exclude atmospheric  oxygen  made  concentration t o operate.  concentration  mg/L)  over a f i v e - d a y p e r i o d ; Further,  f o r b a c t e r i a l o x i d a t i o n with no f i s h  water.  i n d i v i d u a l experiments,  Again  concentration azide  2.0  over  there  examined  (nitrogen  and  allowing  the in  experiments  c o n t r o l t e s t s were  i n the  tanks,  u s i n g oxygen  was no d e t e c t a b l e  24 hours.  fish  by  purged  No d e t e c t a b l e change was observed  over o n l y 24 hours.  before and a f t e r sea  of  The e f f i c a c y of was  oxygen  were conducted  sandwiched  When the r e s p i r o m e t e r s were i n  to  oxygen  with  over the e n t i r e  diameter)  the tanks with oxygen-stripped sea water  respirometer  fitted  X  The b l a n k e t s were  filling an  2.7  with c i r c u l a t i n g pumps (800 L/hr) mixed the  water and maintained a temperature the  (5mm  (4 X  change  both  saturated in  oxygen  A l l oxygen a n a l y s i s was  by the  m o d i f i e d Winkler t i t r a t i o n method ( S t r i c k l a n d and  Parsons  1972); d u p l i c a t e t i t r a t i o n s of two samples determination confidence  with  (n=4) c o n s t i t u t e d  an a n a l y t i c a l p r e c i s i o n of +.0.02  interval).  14  mg/L  each (95%  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 a c t i o n  increment, among  have  a l l been used  SDA, heat  thermogenesis,  t o d e s c r i b e the e l e v a t i o n  expenditure a s s o c i a t e d with i n g e s t i o n of food i n  (Brody 1945,  Beamish 1974,  J o b l i n g 1981). mean  apparent  f e e d i n g metabolism and d i e t a r y induced  others,  energy  (SDA),  elevation  concurrent here.  presented;  K l e i b e r 1975, B r e t t and Groves 1979,  i n equation 1 (chapter 1 ) ,  of  standard  The  animals  In t h i s p r e s e n t a t i o n these terms w i l l be taken to  Rd as presented  actual  of  energy  expenditure,  (Rs) and a c t i v i t y  hence o n l y  exclusive  (Ra) c o s t s i s  the  considered  c o n t r o v e r s y surrounding the cause of SDA  has  some c o n s i d e r SDA t o r e s u l t from c a t a b o l i c  others from anabolism  of  the  been  processes,  or both.  G e n e r a l l y , s t u d i e s have examined SDA u s i n g f i s h e s a c c l i m a t e d to  regularly  fed  meals  of  sizes.  of  consistent.  Energy c o s t s a r e u s u a l l y found to be a  1974,  Davenport 1979).  strikingly f u n c t i o n of  Niimi  Tandler and Beamish 1979,  1972,  Vahl  U n f o r t u n a t e l y , the r a t i o n of f r e e l i v i n g  and  fishes  not match t h a t of l a b o r a t o r y specimens i n e i t h e r q u a l i t y or  regularity. wild  B r e t t 1976,  resulting  are  q u a n t i t y and composition of the meal (Muir and  Beamish  does  metabolic processes  The  measurements  the  digestive  different  Given  the v a r i a b l e s u p p l y of energy  f i s h e s i t would seem reasonable t o suspect  15  available that  to  different  physiological processes, metabolic  in  would be used to a s s i g n  metabolites  e i t h e r c a t a b o l i c or a n a b o l i c , f u l f i l l i n g the need.  specimens, may,  pathways  Differences  i n the d i e t a r y h i s t o r y of  r e s u l t i n g i n d i f f e r e n t metabolite  part,  underlie  the c o n t r o v e r s y  greatest  laboratory  processing  in  the  to  pathways  literature  on  feeding metabolism. This with  study  different  was  initiated  feeding  frequencies  differently  to  experiments  the t o t a l metabolic  by  oxygen  meals  to examine the  (as  measured  followed  before,  feeding  intervals. the  different 2.1  ammonia  and  and  the  measured  to  protein  excretion)  after acclimation  catabolic  In  (as  due  nitrogen  In t h i s manner, i t was  respond  quality.  energy expenditure  that  to  was  different  hoped to gain i n s i g h t s  anabolic  strategies  given  opportunities.  METHODS: The  metabolic  expenditures  of s a b l e f i s h were examined  groups of 5 i n d i v i d u a l s maintained fish  were  0.164  kg S.D.,  held  in  Before 12  and  energy expenditure  by  during,  species' feeding  the s a b l e f i s h might  similar size  consumption) and  catabolism  into  of  possibility  hr  approximately one n=50),  i n the mass r e s p i r o m e t e r s . A l l  kg i n wet  body  s e x u a l l y immature,  weight  (X=1.125  h e a l t h y , and  c a p t i v i t y f o r at l e a s t 6 months p r i o r  and  to  water temperatures at 8.5°+ 0.5° C.  f i s h were fed chopped h e r r i n g and sablefish experiments,  stomachs however,  (McFarlane only  squid, and  Beamish fed.  During  holding,  1983); All  been  kept at  prey commonly found  h e r r i n g was  16  had  +_  experiments.  d u r i n g experiments, photoperiods were normally  and  using  meals  in  during were  approximately feeding  5% o£ the f i s h e s ' wet  frequency  opportunities.  altered  to  body weight ( i . e . simulate  50 g) with  different  feeding  The meals were below the maximum s i n g l e meal s i z e  which v a r i e d i n p r o p o r t i o n to the p r e c e d i n g s t a r v a t i o n time as i s commonly  observed  (Pandian  1967a,  T y l e r and  Dunn 1976).  These  submaximum meals were given because a l l f i s h fed a g g r e s s i v e l y this  level resulting  five  i n d i v i d u a l s i n each r e s p i r o m e t e r .  individuals continued food.  tended  i n an equal d i s t r i b u t i o n of food among  to become sated more q u i c k l y ,  feeding,  for  acclimating  to  because  f e e d i n g frequency  others  began.  The  o b s e r v a t i o n s to be made while the  fish  the d i f f e r e n t r a t i o n  one  Smith  oxygen 1982),  the were  treatment  was  of the experimental  treatments  the same  as  and  the  was  holding  stock.  To e l i m i n a t e the p o t e n t i a l f o r metabolic compensation reduced  some  the f i s h  3 weeks (500 hr) before an experiment  s t a r v a t i o n p e r i o d enabled  necessary  while  the  r e s u l t i n g i n an unequal d i s t r i b u t i o n of  Meals were given weekly d u r i n g h o l d i n g and  starved  were  With l a r g e r meals  at  consumption) a t low oxygen l e v e l s  (i.e.  (Sullivan  the biomass i n each respirometer was  and  selected  to  l i m i t oxygen d e p l e t i o n to not more than 75% of the i n f l o w water's air-saturated  concentration.  During  d e t e r m i n a t i o n , water flow to the tanks was and  consumption  estimates  based on  d i f f e r e n c e between the average of two samples. the  temperatures.  preventing The  sablefish  stratification,  24-hour are  oxygen  consumption  curtailed  f o r 24 hours  oxygen  active  f i n a l water  water pumps c i r c u l a t e d and  maintained  determination period  diurnally  concentration  i n i t i a l and two  Heat exchangers with submersible  water,  because  the  an  and  for  was  water  selected comparative  purposes  I t was  necessary t o keep a c t i v i t y metabolism as constant  as p o s s i b l e between d e t e r m i n a t i o n s . During the same p e r i o d , i n i t i a l taken  1972)  analysis  values.  bottles  contamination,  washed,  rinsed  with  or b a c t e r i a l o x i d a t i o n were made,  No s i g n i f i c a n t d i f f e r e n c e was  initial  and  initial  concentration.  final  contributed  to  during  first  limits  and  concentrations  The  minimizing  respirometer  (Elliott  discontinued after The  these  herring  50  24  hour  monitored  1972),  1979);  between of  the  biases.  the  likely  Further,  differences by  in  urease  urea  method  but were found to be below  consequently  such  of  the  excrete  sampling  was  obtained i n  two  days.  used as experimental  experimental p e r i o d ,  content  each  temperatures  potential  food was  l o t s from a s i n g l e s u p p l i e r and maintained the  found  of d e t e c t i o n even i n s t a r v i n g f i s h which tend to urea  of  regardless  low experimental  were  Parsons  f i s h in  low s u r f a c e to volume r e l a t i o n s  experiments,  concentration  (Strickland  more  ammonia  l a r g e r e s p i r o m e t e r s and  nitrogen  copious  without  by comparing ammonia c o n c e n t r a t i o n s of  experimental s e r i e s .  the  sample  then f l u s h e d twice with sample water  water samples taken 24 hr apart a t the beginning and end  such  over  Tests of the mass r e s p i r o m e t e r s f o r p o s s i b l e ammonia  contamination tanks,  To minimize  were a c i d  amounts of d e i o n i z e d water, before use.  (Strickland  c a l i b r a t e d to ammonium c h l o r i d e standards  the range of expected  the  f i n a l water samples were  f o r ammonia a n a l y s i s by the indophenol method  and Parsons  and  and  the proximate was  f r o z e n a t -30  composition and  of  the  herring  determined  consistency  and  permit e s t i m a t i o n of n u t r i e n t 18  reqularly  C.  Over  caloric  to  check  budgets.  Water  content and the wet  c a l o r i c v a l u e s were determined by  oxidation  method r e s p e c t i v e l y using  f i s h homogenates f o r a c i d d i g e s t i o n 1978,  Mackereth et a l .  made  following  Bligh  chloroform,  water  homogenate.  After  500  lipid  justified tissue  by  agreement  and  the  1979) after  (1959)  The  separation  a of  d r i e d residue  weighed. i t s ash  and  was  methanol, whole  The  was  dried  then ashed  weight  content was  was  fish  difference  considered  an  This approach  is  content  of  fish  checked by comparing proximate  kcal/g,  to those from wet  lipid  = 9.45  oxidation.  c o r r e c t i n g f o r the d i f f e r e n t  expenditure and  four r a t i o n treatments: fish  (this  kcal/g, Both  Brett  were  nitrogenous  f o r proximate values and  nitrogen  in end-  ammonia f o r  2) 1.25%/day,  to r a t i o n s of  nitrogen  excretion  acclimation pattern,  hr) had  fast.  Results  been reached,  as  :  1) 0% of 4)  wet  0.36%/day).  f i s h ) f o l l o w i n g an daily  5 to 7  feedings.  the  initial 3 and  i n d i c a t e d by a c o n s i s t e n t  were continued f o r a f u r t h e r 19  herring  a n a l y s i s began with  were t a b u l a t e d  in  4) every 14 days  3) 0.71%/day, and  f i r s t meal (or only meal f o r s t a r v e d (500  were examined  2) 50 g chopped  3) every 7 days, and  i s approximately e q u i v a l e n t  Oxygen consumption and  excretion  1) s t a r v a t i o n ,  fed every 4 days,  body weight/day,  week  using  digestion). Energy  per  content were  i n s i g n i f i c a n t carbohydrate  products (molecular n i t r o g e n acid  Estimates of l i p i d  food's crude p r o t e i n content.  ( C r a i g et a l . 1978)  Groves  C r a i g et a l .  and  the ash  c a l o r i c v a l u e s ( p r o t e i n = 5.66 and  l y o p h i l i z e d whole  e x t r a c t i o n , the s o l i d r e s i d u e  the d r i e d r e s i d u e  estimate of the  the  and  (Maciolek 1962,  Dyer  weighed.  C f o r 24 hr and  between  and  extraction  a t 95 C f o r 48 hr and at  1978).  lyophilization  after SDA  2.2 RESULTS: Oxygen  consumption  acclimation, data.  Starved  days SDA  show  ,  4 days,  the  every  45  14  due to  t h i s response subsided a f t e r  a 30 mg/kg/hr i n c r e a s e i n  oxygen  returned to a constant r o u t i n e r a t e of 60  only  in  7 days  mg/kg/hr.  f i s h a c c l i m a t e d to feedings every four or seven  experienced  which  days  the  ration  i n c r e a s e i n oxygen consumption r a t e ,  a constant or r o u t i n e l e v e l of about  Conversely, days  after  two d i s t i n c t p a t t e r n s appeared  of about 15 mg/kg/hr; reached  2.1),  (Fig  f i s h and f i s h a c c l i m a t e d t o food once  had an i n i t i a l  and  in  that  rates  although  consumption  mg/kg/hr  t h i s r o u t i n e r a t e c o u l d only be  after  confirmed  the weekly fed f i s h where a steady s t a t e was reached  after  4  ( F i g . 2.1). Maximum oxygen consumption occurred  before  and a f t e r r a t i o n a c c l i m a t i o n .  i n the f i r s t However,  24 hr  both  the maximum f o r  f i s h a c c l i m a t e d t o meals every 4 and 7 days was approximately  50%  greater  and  than f o r the same f i s h  following i n i t i a l  those a c c l i m a t e d t o meals every 14 days. later, routine energy  starvation  T o t a l SDA,  r e f e r r e d to  i s the area under the oxygen consumption curve above  the  oxygen consumption r a t e ( F i g . 2.1) and represented  the  expended  on  food p r o c e s s i n g e x c l u s i v e of  standard  and  a c t i v i t y metabolism. Oxygen consumption r a t e s d u r i n g the a c c l i m a t i o n p e r i o d ( F i g . 2.2A and 2.3A, were  feedings 2,  intermediate  condition.  in  3,  and 4) showed SDA p a t t e r n s which  magnitude to the s t a r v e d  and  acclimated  The high v a r i a b i l i t y of these means r e s u l t e d  gradual t r a n s i t i o n between  feeding  20  states.  Changes,  from the resulting  1  2  3  U 5 6  7  8  9 10 11 12 13 14  Days Post-prandial  Figure 2.1. Oxygen consumption of s a b l e f i s h acclimated to different feeding intervals (4, 7, 14 days and s t a r v e d ) . V e r t i c a l l i n e s through each mean equal one S.D. and sample s i z e s correspond t o those i n F i g s . 2.5-2.8. 21  Figure 2.2. Oxygen consumption (A) and ammonia nitrogen excretion (B) of s a b l e f i s h before (dots: feeding 1 ) , during (triangles: feedings 2-4), and a f t e r (squares: feedings 5-9) a c c l i m a t i o n t o weekly meals. V e r t i c a l l i n e s equal one S.D. and numbers correspond t o sample s i z e s and are the same i n A and B. 22  1 2  3  4  1 2 Days  3  4  Post-prandial  Figure 2.3. Oxygen consumption (A) and ammonia n i t r o g e n excretion (B) of s a b l e f i s h before (dots: f e e d i n g 1), during (triangles: feedings 2-4), and a f t e r (squares: feedings 5-9) a c c l i m a t i o n 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 s i z e s and are the same i n A and B. 23  from  acclimation,  ration  o n l y be  treatments as the  with the s t a r v e d fish  can  before  condition  a  f o r the  14-day treatment showed ( F i g . 2.1).  fed every 7 days ( F i g .  time  Illustrated  constant  2.2A)  there was  routine  rate  was  reached.  consumption became constant  however,  fasted  and  decrease over a week-long p e r i o d Ammonia consumption  rates  (r =0.94,  fish  two and  n=289), latter  consequently they  (Fig.  fed every 14 days and  2) f i s h  2.4):  weekly fish  i s r e l a t i v e l y greater. first  nitrogen  fish  d i f f e r e n c e occurred fish  excretion rates  acclimated  to three  to meals  consumption energy  1)  2.4).  starved and  during  f a i r l y constant of  (cal  total  two  occured  = 3.25  expenditure due  X mg  day  meals  after In  Another 4 days f o r  these  level,  fish  whereas  markedly on the seventh  expenditure  to p r o t e i n c a t a b o l i s m  day  3 days. based  oxygen consumed,  24  to  weeks.  2.2B).  f o r the preceding energy  of  times those f o r starved  every  to weekly meals ( F i g .  7 SDA  effect  acclimated  i n the r o u t i n e r a t e achieved  ammonia n i t r o g e n e x c r e t i o n d e c l i n e d  Estimates  and  the  oxygen consumption a t t a i n e d a r e l a t i v e l y constant  a f t e r being  followed  Maximum r a t e s again  excretion rates in f i s h  acclimated  to  oxygen  24 hours f o l l o w i n g i n g e s t i o n , however, f i r s t  or every 4 days were two or  days;  fed every 4  the p a t t e r n of oxygen consumption r a t e s ,  ammonia  nitrogen  (Fig.  2.3B,  shared  the  ammonia  2.2B,  Although  during  4  ( F i g . 2.2A).  days.  acclimation  after  f i s h the r a t e continued  data groupings were evident fish  the  After  e x c r e t i o n r a t e s were h i g h l y c o r r e l a t e d with 2  much the same p a t t e r n as the Again,  difference  a l s o a change i n the  oxygen  acclimating  no  7-day  During a c c l i m a t i o n of  acclimation, in  4 and  on  oxygen  B r e t t 1985)  (cal =  mg  and  ammonia  1  2  3  U 5 Days  6  7  8  9 10 11 12 13 \U  Post-prandial  Figure 2.4. Ammonia n i t r o g e n e x c r e t i o n of s a b l e f i s h a c c l i m a t e d to d i f f e r e n t f e e d i n g 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 s i z e s correspond t o those i n F i g s . 2.52.8 25  n i t r o g e n X 6.25 mg p r o t e i n / mg ammonia n i t r o g e n X 4.70 c a l / protein,  Brett  difference excretion  and  Groves  1979)  between  oxygen  consumption  was  and  always  much  appeared  greater  than  that  to  remain f a i r l y constant  energy expenditure  attributable  For  expenditure to  fuel  2.8).  by p r o t e i n  protein  catabolism  total  although  the  constant.  a much g r e a t e r  p r o p o r t i o n of the  from  expenditure  suggested protein  that,  first  than f o r s t a r v e d  however,  on  days, values second  accounted f o r by  i t remained much greater  f i s h and those fed every 14 days.  26  two  Beyond the  the p r o p o r t i o n of t o t a l energy expenditure  2.7  slightly  of p r o t e i n energy  i n d i c a t e d t h i s d i f f e r e n c e might not be r e a l .  declined,  based  catabolism  f o r the  r e l a t i v e l y high v a r i a n c e  catabolism  total  fed weekly and every 4 days ( F i g .  energy  energy  starvation.  i n c r e a s e d s l i g h t l y while  both cases the data  excretion,  exceeded  provided  i n the f i s h  In  u n t i l day 24 of  remained r e l a t i v e l y  Protein catabolism  protein  fate  T h i s f r a c t i o n d e c l i n e d s t e a d i l y over 14 days then  Beyond 24 days p r o t e i n c a t a b o l i s m  metabolic  nitrogen  ( F i g . 2.5 and 2.6). Immediately f o l l o w i n g feeding the  was g r e a t e s t .  day,  ammonia  feeding o p p o r t u n i t i e s .  p r o p o r t i o n of t o t a l metabolism represented  ammonia  proportional  f i s h and f i s h fed every 14 days, t o t a l energy  catabolism  and  the  r a t e s and were compared t o examine the metabolic  of n u t r i e n t s i n f i s h given d i f f e r e n t starved  reflected  mg  Figure 2.5. Total energy expenditure (based on oxygen consumption: squares) compared t o t h a t a t t r i b u t a b l e t o p r o t e i n catabolism (based on ammonia nitrogen excretion: triangles) d u r i n g s t a r v a t i o n f o l l o w i n g a s i n g l e meal. V e r t i c a l l i n e s equal one S.D. and numbers are sample s i z e s which are the same f o r c o r r e s p o n d i n g means. 27  '  •  t  I  1  2  3  U  I  I  I  I  I  5 6 7 8 9 Days Post-prandial  I  I  I  )  I  10 11 12 13 14  Figure 2.6. Total energy expenditure (based on oxygen consumption: squares) compared t o t h a t a t t r i b u t a b l e t o p r o t e i n c a t a b o l i s m (based on ammonia n i t r o g e n e x c r e t i o n : t r i a n g l e s ) a f t e r acclimation to meals every 14 days. Vertical lines equal one S.D. and a l l sample s i z e s are 7. 28  400  320  JZ  "5 240' u cu D  TO  ccu  Q. X  LU  160'  c? (D C LU  80  1 Days  2 3 Post-prandial  Figure 2.7. Total energy expenditure (based on oxygen consumption: squares) compared to that a t t r i b u t a b l e t o protein c a t a b o l i s m (based on ammonia n i t r o g e n e x c r e t i o n : t r i a n g l e s ) a f t e r a c c l i m a t i o n 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 s i z e s are 7. 29  4 0 0 i  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 t o t h a t a t t r i b u t a b l e t o p r o t e i n c a t a b o l i s m (based on ammonia n i t r o g e n e x c r e t i o n : t r i a n g l e s ) a f t e r a c c l i m a t i o n t o weekly meals. V e r t i c a l l i n e s equal one S.D. and a l l sample s i z e s a r e 5. 30  2.3  DISCUSSION: Changes  long  term  1964a,  in routine food  metabolic  deprivation  Mann 1965, this  oxygen  consumption d e c l i n i n g  fed  once  physiological  every  expenditure (Fig.  not  only  fed  deprived match  an  fish of  food of  Situations  response  Dickie It  state  an a d e q u a t e  (1966a) may  and K e r r be  argued that  weekly  every  metabolites  The c o n s t a n t  routine  unprocessed  2.1),  the  fish  same  and 2 . 3 ) . feeding food  than  were  in  again  fall  to  manner  as  This  suggests  opportunities.  supply  activity  for  growth  i n which food  is  and c o n s e r v a t i o n  of  hypothesized  is  the  by P a l o h e i m o and  elevation  routine  s i m p l y due t o  from i n c o m p l e t e  rate,  achieved  indicates  metabolites  apparent  SDA and a t  4 days,  unprocessed  (Fig.  subsequent  (1982).  both d u r i n g  and  seventh  would g r a d u a l l y  whereas t h o s e  as  energy  starvation  but  these  those  total  f o u r t h and  i n much t h e 2.2  state  and  of  to  routine  considerably greater  different  supplies,  consumption,  weekly  is  (Fig.  metabolic  energy  every  (Beamish  with  of  with  appear  fish  16 d a y s  Presumably i f  to  2.1)  metabolism,  require c u r t a i l e d metabolic  restricted  (Fig.  about  individuals  provide  Sablefish  decline  meals  metabolic  starved  p e r m i t an e l e v a t e d  the  2.1).  their  which  to  species  in starving  This  digestive  acclimation occurred  adaptive  limited  steadily  metabolism  (Fig.  1986).  stop after  initial  routine  that  gradual  to  been a s s o c i a t e d  fish  characteristic  Once a c c l i m a t e d  nondigestive poorly  al.  weeks.  appears  2.5).  day,  two  have  in several  DuPreez et  share  rates  on t h e  this  accumulated,  31  is one  an  SDA  rate,  of  oxygen  in fish  fed  accumulation  of  between  feedings.  f o u r t h d a y by f i s h not  the  case.  would e x p e c t a  fed Had  steady  d e c l i n e i n oxygen consumption u n t i l the next if  metabolites  consumptions constant  or  to  rise  of  this  mitochondrial may  maximum  SDA  as  prolonged  fish  600 mg  f o r higher SDA,  SDA  rather  (Elliott  f e d weekly,  reach rate  a  for  (Furnell  although  cellular  that  oxygen  1979).  If  but r a t h e r have  information  presented  e l e v a t i o n i n t o t a l metabolism  uptake cellular  then i t i s  the  i n chapter  maximum  SDA  metabolites. 3,  collected  suggests that much of the  i s due t o i n c r e a s e d  standard  and  metabolism.  The  change  opportunities,  i n metabolic  status,  with  i s p a r a l l e l e d by a s h i f t  t o power metabolism.  different  i n the  energy  feeding sources  The s m a l l p r o p o r t i o n of t o t a l  expenditure from p r o t e i n c a t a b o l i s m i n p o o r l y f e d f i s h and  oxygen  f e d every 4 days would have the same d e c l i n e  synchronously d u r i n g these experiments,  used  not  oxygen/kg/hr  beyond 24 hours to e l i m i n a t e the s u r p l u s  activity  activity  and  i s l i m i t i n g and m e t a b o l i t e s accumulated,  not l i k e l y t h a t f i s h  The  i s about  catabolic rates,  limit  catabolism  t h a t observed  As the a c t i v e metabolic  there i s c l e a r l y scope  rates,  in  beyond  size  Further,  one might expect the maximum  low-variance mean.  sablefish 1987),  accumulated  feeding.  energy  (Fig.  2.5  2.6) becomes v i r t u a l l y the o n l y source i n f i s h f e d weekly and  every f o u r t h day ( F i g . sablefish inverse  have  a  2.7 and 2.8).  p o s i t i v e energy  proportion  energy  accumulation,  feeding  treatments.  At a l l f e e d i n g l e v e l s the balance  which  t o the f e e d i n g i n t e r v a l  (Table  however,  differs  In the f o l l o w i n g d i s c u s s i o n ,  32  declines 2.1).  i n composition  in This  between  i t has been assumed, a p r i o r i ,  Table basis,  2.1. Energy, p r o t e i n and l i p i d b u d g e t s , on a p e r for s a b l e f i s h with d i f f e r e n t feeding opportunities.  meal  Feeding Interval 4 days 7 days 14 d a y s  Parameter 1)  P r o x i m a t e c o m p o s i t i o n of f o o d : i) Protein a)g/meal b)kca1/mea1 i i) Lipid a)g/meal b)kcal/meal iii) Total Energy (kcal/meal)  8 . 10 45 . 85 2 . 00 18 . 90 64 . 7 5  8 . 10 4 5 . 85 2 . 00 18 . 90 64 . 75  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 intake) : i) Protein a)g/meal b)kcal/meal ii) Lipid a)g/meal b)kcal/meal iii) Total Energy (kcal/meal)  0 . 41 2 . 29 0 . 10 0 . 95 3 . 23  0 . 41 2 . 29 0 . 10 0 . 95 3 . 23  0 . 41 2 . 29 0 .10 0 .95 3 . 23  0 . 842 5 . 00  1. 271 7 . 55  0 .675 4 .03  8 .10 45 . 8 5 2 .00 18 . 9 0 64 . 7 5  2)  3)  E x c r e t o r y l o s s (based excretion) : i ) Ammonia N e x c r e t e d  5)  6)  7)  ammonia  a)g/meal b)kcal/meal (g X 5 . 9 4 ) a)g/meal b)kcal/meal  5 . 26 24 . 72  7 . 94 37 . 32  4 .24 19 . 9 3  M e t a b o l i c energy expended (based 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  11866 38 . 56  16277 52 . 90  Protein balance (ration catabolized protein): i) g/meal ii) kcal/meal  2.43 13.75  -0.25 -1.42  3.45 19.53  ii) 4)  on  Protein catabolized ( g a m m o n i a N :X 6 . 2 5 )  -  faecal  Energy balance (ration - faecal ammonia - m e t a b o l i c e n e r g y ) : i) kcal/meal  -  -  L i p i d balance (diet - faecal l i p i d (metabolic - protein energy)): i) kcal/meal ii) g/meal  33  32.26  15.41  4 . 59  18.41 1.95  16.71 1.77  -15.02 -1.59  that and  f i s h are m e t a b o l i z i n g a mixed l i p i d and an  o x y c a l o r i f i c e q u i v a l e n t of 3.25  applies that and  ( B r e t t 1985).  the  exactly correct.  cal/mg  substrate,  oxygen  i s a f u n c t i o n of  ration  o x y c a l o r i f i c e q u i v a l e n t of  treatment  3.25  F o r t u n a t e l y , the e r r o r i s not great assuming an e q u i v a l e n t of 3.28  and  Brafield  for protein,  conclusions  1985)  fed  fish  c a t a b o l i z e the  d e r i v e much of t h e i r energy from l i p i d the lower between-meal, two  nitrogen others  (Gerking  faeces  a  g  five  gain  kcal.  of 3.45  least  every  two  combination  the  protein  and  t o t a l ammonia e x c r e t i o n seen i n f i s h  fed  A similar relationship  excretion 1971,  o x i d a t i o n as  p a t t e r n has been  S a v i t z 1969,  1971,  l o s s of p r o t e i n and  b,  Gerking  1955,  g from each 8.1  Elliot  1971),  however,  and weeks of  by  1976b).  energy  there  g i n a meal f o r  in  i s a net fish  fed (3.45  the t o t a l energy g a i n i s only  4.59  to be  endogenous  the  kcal  i s consuming i t s appear  in  observed  lipid  T h i s means t h a t the f i s h has a negative kcal  affect  T h i s r e p r e s e n t s an energy g a i n of 19.5  kcal/g),  -15.0  lipid  by  percent  1967a,  14 days.  X 5.66  for  indicated  (Table 2.1).  1955,  (Pandian  protein every  weeks  consumption,  Assuming  does not  not  reached.  Infrequently  every  and  is  (1 - 2% of  t o t a l energy expenditure 3.19  consumed  Based on t h i s assumption, i t becomes c l e a r  the l i p i d : p r o t e i n r a t i o consequently  protein  lipid  body r e s e r v e s . sparing  and  The  protein  exogenous  balance fish  and  lipids  fed  using to  of  a  power  metabolism. Conversely, but  a  weekly fed f i s h show a negative  t o t a l energy g a i n t h a t i s an order  than f i s h fed every two  weeks.  The 34  of  negative  protein  balance,  magnitude  greater  p r o t e i n balance  may  be  an  artifact  of the high n i t r o g e n e x c r e t i o n observed  first  two days post p r a n d i a l f o r the two higher  (Fig.  2.4). Energy expenditure estimated from ammonia e x c r e t i o n  (i.e.  protein  oxygen fish  catabolism)  consumption  (Fig.  greater  fed  i n the  than t h a t  treatments  calculated  2.7 and 2.8) cannot occur  unless  operate a n e r o b i c a l l y i n v o l v i n g gluconeogenesis from  acids,  followed  by  glycolysis,  is  also  an  little  unlikely  and  process.  There  metabolism  g i v e n the low l e v e l of metabolic a c t i v i t y  and high oxygen c o n c e n t r a t i o n s .  reason  to  from the  ammino  inefficient  expect  anerobic  (Fig.  2.1)  A more l i k e l y e x p l a n a t i o n i s the  methodological r e s u l t of anomalous water a n a l y s i s a t high ammonia c o n c e n t r a t i o n s , which were e x t r a p o l a t e d because standards i n the c a l i b r a t i o n curve. basis,  weekly  fed  fish  do  they exceeded the  None-the-less, on a per meal  appear  to  have  a  lower  r e t e n t i o n e f f i c i e n c y than the other two treatments.  Despite the  low or negative p r o t e i n balance of weekly fed f i s h , positive fish  lipid  fed  available  every  balance of approximately the same four  days and almost equal to  i n the d i e t .  protein  they have magnitude  a l l the  a as  lipid  With weekly feedings the f i s h appear  to  have s u f f i c i e n t s u r p l u s p r o t e i n such t h a t excess can be used as a metabolic energy source while l i p i d  becomes the p r e f e r r e d storage  mater i a l . F i s h fed every f o u r t h day e l a b o r a t e t i s s u e both from and  p r o t e i n i n the d i e t .  represents energy  The p o s i t i v e p r o t e i n balance  13.8 k c a l of energy,  balance.  Again  i t is  18.5 k c a l l e s s than likely  the  ammonia  lipids (2.43 g)  the  total  analysis  underestimated p r o t e i n r e t e n t i o n which may r e p r e s e n t the 0.5 k c a l of  energy  balance  unaccounted 35  f o r by  protein  retention  and  dietary lipid  energy.  It  difficult  is  physiological intake  to s p e c u l a t e  strategies  i n the d i f f e r e n t  on the  significance  used by s a b l e f i s h to p a r t i t i o n f e e d i n g environments.  of e l a b o r a t i o n i n w e l l - f e d  fish  when  s u f f i c i e n t p r o t e i n i s a v a i l a b l e i n the d i e t .  energy e x p e n d i t u r e s . is  retained  increase (Fig.  in  2.5)  greater  and  energy that  i s the p r e f e r r e d s u b s t r a t e  every 4 days,  protein catabolism  In f i s h  are used  to  power  reserves  protein  metabolism.  ammonia e x c r e t i o n i n f i s h s t a r v e d suggests t h a t as l i p i d  fed  can account f o r most  As f e e d i n g becomes l e s s frequent,  lipids  the  I t appears  lipid  weekly and  of  beyond  become  The  24  days  depleted,  p r o p o r t i o n of t o t a l energy i s again d e r i v e d  a  from p r o t e i n  catabolism. The rates  c o r r e l a t i o n of oxygen consumption and  suggests t h a t SDA  amino a c i d deamination. after  acclimation,  energy  balance,  argues  against  source  of  correlated  The  t o t a l SDA  growth r a t e s ,  the hypothesis  SDA. 2  with  2.2),  although the  total  different.  This  are q u i t e  the  SDA  protein  observed  is  protein  difference  balance  between  r e l a t i n g p r o t e i n balance  account f o r some  36  It  show  a  Consequently, (Y),  great the  (Y = 16.68(X) +  the  should,  r e l a t i v e difference in  calculations  (X) to SDA  directly  l i p i d , may  is l i t t l e  tretments.  the  indicating  of the p o s t - p r a n d i a l e l e v a t i o n of oxygen consumption.  while  are  balance,  a s s i m i l a t i o n of p r o t e i n , although not  however, be noted t h a t there  or  i n a l l r a t i o n treatments,  t h a t a n a b o l i c processes  Conversely,  (r =0.83)  excretion  i s a s s o c i a t e d with p r o t e i n c a t a b o l i s m  i s s i m i l a r (Table  or  ammonia  SDA  relative equation 1539),  Table 2.2. Estimates of SDA and r o u t i n e metabolic r a t e , on a per meal b a s i s , f o r s a b l e f i s h with d i f f e r e n t feeding o p p o r t u n i t i e s . Feeding  Interval  4 days  7 days  Routine oxygen consumption r a t e (mg/kg/hr)  64.5  61.5  43.7  SDA - t o t a l oxygen consumption above the r o u t i n e r a t e between meals (mg)  1563  1539  1608  SDA - as a percent of food energy consumed (assuming 3.25 cal/mg oxygen)  7.8  7.7  8.1  indicates  that  significant routine that  SDA  p r o t e i n balance  consumption  metabolic r a t e .  catabolic  minor two  when  of 1539  That  for  catabolism  is  i s zero there i s mg  of  From t h i s evidence,  oxygen  derived  weekly  The  SDA  from both p r o t e i n and  fed  fish  results  of  primarily  the  with  f o r f i s h fed lipid  a  conclude  SDA  a  every  catabolism.  from  with a minor c o n t r i b u t i o n from l i p i d s .  fed every f o u r t h day  still  above  one would  processes are the primary cause  c o n t r i b u t i o n from anabolism. weeks  14 days  protein  SDA  i s a t t r i b u t e d almost e x c l u s i v e l y to  in  fish  protein  catabolism. In  summary,  metabolite  these r e s u l t s i l l u s t r a t e the dynamic nature of  h a n d l i n g and  experimental  animals.  respond  similar  to  importance ration  of  i t s dependence on the feeding Feeding h i s t o r y determines  meals.  T h i s study a l s o  i s achieved and v a l i d 37  to  metabolic  of  sablefish  demonstrates  monitoring experimental parameters  acclimation  how  state  know  the when  comparisons  can be made. reached  over  these. to  Further,  the r e l a t i v e l y s h o r t term of experiments  Obviously  deplete  acclimated,  i t cannot be concluded t h a t a c c l i m a t i o n i s  the  their would  f i s h fed every two lipid  have to e v e n t u a l l y pursue another  metabolite  indefinately  elaborate  these  Simlarly, tissue  and,  fish  i n the  fed weekly form  of  could  lipid  a p o i n t of imbalance i n proximate composition. acclimation  states  are  stability  dependent  on the past  level  nutrition  and  of  continue  apparently  strategy.  reaching  weeks could not  as  although  partitioning  reserves  such  transient feeding  phases history,  f u t u r e maintenance  viability.  38  of  the  not  without Clearly  of  relative  the  current  organism's  CHAPTER  3:  THE EFFECT OF RATION ON THE A C T I V I T Y AND STANDARD METABOLISM OF SABLEFISH  3.0  INTRODUCTION: The  r e s p i r a t o r y metabolism of  as  consisting  3)  standard  of  three  metabolism.  metabolism  are  Davis  F r y 1971,  1967,  energy  referred  expenditure  digestive  components:  of  metabolic  rates  The  metabolic  an  to  as  Vahl  of  active  additional  level  been  of  activity  measurements.  The a d v a n t a g e  of  on  they a l s o  activity  recorded (Brett for  fish 1965,  spontaneously  Mookherjii variable The terms  of  different to  exclusive  for  1964,  yield  a  have  fish  component  in  of  1964b, to  metabolism fish  is  in a tunnel  respirometer.  39  document, consumption data  fish  are  spending  This  is  usually  forced  c, an  activity but  rarely  Beamish  and  independent  usually described  velocities  an e s t i m a t e  to  it  level.  of  no a c t i v i t y  because  B e a m i s h 1970)  expenditure  of  1987).  of  energy  level  and D u P r e e z e  these a d d i t i o n a l  relation  the  (eg.  oxygen  levels  or r a t i o n  and  reported  energy  (Beamish  especially  (Warren  studied  and  1973,  standard  and  been  less  the  and  The r o u t i n e  standard rate.  B r e t t and G l a s s  temperature  activity the  the  of  under d i f f e r e n t  1964)  s u c h as  of  active  fish.  collecting  estimates  and  experimentation  synchronous  that  digestion,  which r e p r e s e n t s  and D a v e n p o r t 1979, has  recognized  metabolism  many f i s h  rate  2)  activity  routine  specifically,  is  generally  activity,  Together,  spontaneously  1972,  requires  1)  is  B r e t t and G r o v e s 1979)  M u i r and N i i m i standard  fish  swimming a t  can then  a series  in of  By e x t r a p o l a t i n g be made  of  the  standard metabolic r a t e , absorptive relative  fish to  efficient  energy  swimming  swimming energy 1978,  (Fry  the energy 1947).  By  consumption, speeds.  r e l e a s e d by a r e s t i n g , p o s t examining one  can  T h i s leads to  expenditures of w i l d f i s h  estimate  the  hypotheses  (Ware 1975,  most  on  1978,  the Jones  1982).  information  about  expenditures  of  spontaneously  a c t i v e f i s h nor what c o n t r o l s t h e i r a c t i v i t y .  It  at  of  overall  energy  speeds g i v i n g the g r e a t e s t e n e r g e t i c e f f i c i e n c y if  they  do not swim c o n t i n u o u s l y ,  the  temporal  density  of  where  distribution  swimming  (Ware  no estimate can  of energy,  accumulation  (Ware 1975).  would  Although  was  to  environmental  intake  primary  the and  of  f i s h spent swimming e s p e c i a l l y i f  activity  expenditure  1982).  t h i s has been examined f o r f i s h a c t i v e l y f e e d i n g  (Hunter  c o n s i d e r a t i o n must a l s o be given t o the  spent seeking prey between meals. Such a s i t u a t i o n may s c h o o l i n g prey where p r e d a t o r y behavior while  for  contagiously distributed  than  when f e e d i n g on them.  while r e s t i n g and w a i t i n g . of  food  (Kerr  Thomas 1974),  mobile,  the  be reasonable t o assume t h a t the a v a i l a b i l i t y  the  be  details  Further,  but a l s o the r a t e of energy  prey might i n f l u e n c e the energy foraging  activity.  be r e l a t e d  1978).  swimming a t d i f f e r e n t speeds not o n l y v a r i e s  expenditure  It  may  of  little  foraging  of t h e i r t o t a l a c t i v i t y energy expenditure without  efficiency  and  approach g i v e s  been shown t h a t w i l d f i s h would optimize growth by  However, made  the  this  velocity  Kerr  has  Unfortunately,  swimming  the study was  s c h o o l s would be Alternatively,  The  quite  time  occur with searching different  prey can be l o c a t e d  primary o b j e c t i v e of t h i s p o r t i o n  t o examine the energy 40  that s a b l e f i s h  routinely  expend on locomotion  3.1  when given d i f f e r e n t  feeding opportunities.  Methods: Activity  metabolic rates  measurements  were  made  synchronously  measurements d e s c r i b e d i n chapter  2.  with  Fish  metabolic  are o f t e n measured i n s m a l l c o n t a i n e r s which r e s t r i c t  f i s h e s ' movements and do not a l l o w the f u l l activity mass  to occur.  only  meters.  five,  one  opportunity  to  scope of  spontaneous  each The  kg  equipped  with  two  o b j e c t i v e i n using such l a r g e  fish  display  per  tank  was  spontaneous  eliptical  negotiate  shape presented  to  allow  activity  and  tanks  for  them  full  avoid  the  the  varying  contour  The  f o r the  fish  i n t h e i r normal c i r c u l a r swimming p a t t e r n s .  Observerations showed  no abrupt  L  mechano-electric  r e s t l e s s d a r t i n g and a g i t a t i o n o f t e n seen i n c o n f i n e d f i s h . tank's  the  These experiments were conducted i n 4000  respirometers  activity  to  the  made while doing t a i l  f i s h to be r e l a x e d ,  usually  p e r i o d s up to 30 minutes,  beat  frequency  swimmming  counts  slowly  for  then r e s t i n g f o r a s h o r t time  on the bottom before resuming swimming. T a i l b e a t f r e q u e n c i e s were recorded, a f t e r the PVC to  blanket c o v e r i n g the s u r f a c e was  compare swimming speeds between treatments.  tank  were covered  disturbances.  pattern.  A b r i e f a c c e l e r a t i o n of 1-6  a  coasting  glide.  The  fish  swam i n a  in  burst  I n d i v i d u a l o b s e r v a t i o n s were  p a r t c o n t r o l l e d by the d u r a t i o n  41  The of  and  eliminated and  t a i l b e a t s would be  random l e n g t h s of time u s i n g a stopwatch. was  observer  by a black p o l y e t h y l e n e t e n t which  external  by  The  removed,  glide  followed made  for  observation period activity.  If  the  observed  fish  r e s t e d 15 sec or l e s s a f t e r a count s t a r t e d  the  r e s u l t was ignored as i t was d i f f i c u l t t o make a c c u r a t e counts of short  duration.  minutes and  Individual  i n duration  15  r e c o r d i n g s were  (X = 1.63 + 0.31 S.E.  individual  observations  were  generally  n = 1445). made  1  - 3  Between 5  during  a  24  hr  exper iment. A c t i v i t y data i n t h i s paper are r e p o r t e d as counts per day. T h i s r e p r e s e n t s the sum of counts f o r both meters activity salt  meters used  water,  sensitivity  and (Fig.  The  reliable  near  were designed t o be simple, easily  adjusted  3.1).  s t e e l rod suspended  i n a tank.  to  increase  or  The meter was simply a n i c k e l  i n s i d e a copper tube.  which  bottom. line the  lead weight of 15 g was a t t a c h e d t o the end  and kept i t t a u t . water near i t ,  pendulum  the were  completed.  Both the  part  which  of  the  mass  line,  of  single  the  the  circuit  tube  the  lead  satisfactory.  weight  of the meter could be lead  weight  diameter of the  of the pendulum.  daytime a c t i v i t y , g  a  sensitivity  r e l i a b l y showed l i t t l e  15  swirled  the n i c k e l p l a t e d pendulum was d e f l e c t e d and  copper tube s u r r o u n d i n g i t .  The  monofilament thickness  When a f i s h s t r u c k the l i n e or  of the  event  adjusted  suspended copper  and  contact  Contacts were recorded on an E a s t e r l i n e Angus  recorder. altering  monofilament  hung i n the tank from the s u r f a c e t o one cm o f f the  A  contacted  plated  The end of the rod or  pendulum was a t t a c h e d to a 0.5 kg breaking s t r e n g t h line  decrese  tube,  from  by the  or the  The best c o n f i g u r a t i o n of the meter  or no n o c t u r n a l a c t i v i t y ,  but s u b s t a n t i a l  a p a t t e r n confirmed by v i s u a l o b s e r v a t i o n . with a 1.25  By u s i n g two meters 42  cm  diameter  i n each tank,  copper  tube  A was  more counts per  LEAD WIRES BEDDED IN SILICONE SEALANT  HOUSING  1.25cm DIA. COPPER TUBE EVENT RECORDER JACKS  -PENDULUM 2.5cm HOOK  WATER S U R F A C E MONOFILAMENT LINE  L E A D WEIGHT BOTTOM  gure 3.1. The a c t i v i t y meter.  day c o u l d be recorded without u s i n g e x c e s s i v e l y s e n s i t i v e meters. The each  two  other  identical might the  mass with  the  positions.  have  produced  swimming  a c t i v i t y  fish  treatment  differences to  To  the  in  v a r i a b i l i t y  of  as  tank  the  of  equipment  in  both  data,  was  rate  used  to  feeding  slight  experiments, not  the  intertank  experimental If  by  with  against  tanks.  the  configuration  space  encounter  each  during  images  equipment  way  for  mirror  other  protect  from  unnoticed  in  their  counts  equally  up  and  the  further  activity  occur  set  differences  influenced  recorded  did  were meters  differences and  the  were  activity  Minor  meters.  differences,  added  respirometers  meter  they  only  intertreatment  differences. Activity water for  samples half  the  an  surface  the  were hour  showed  no  introduced  a l l  before  a l l  the  before  did  Tanks  were  direct  room  the  room  observed  did  not  did for  not  t a i l  fish  produce cause beat  were  the  to  with  apparent  44  were  in  to  12  the  end  of  a l l  was (1  -  The  tanks  in  black room  photoperiod.  so  in  that  tank  hr  water.  the  it  the  floor,  place  herring  eat  in  in  last  manipulations  enclosed  responses  counts.  By  engaged.  a  the  order  chopped  a c t i v i t y  the  in  cover  the  maintain  vibrations  frequency  to  completely  other  on  fish.  allowed  meters  contact  any  the  after  generally  turned  fed,  fish  were  and  was  habituated  prevent  the  were  agitate  fish  equipment  disturbing  the  not  and  immediately  PVC cover  a c t i v i t y  to  on  meters  were  tanks  from  in  the  When  tents  not  The  fish  the  ancillary  polyethylene  switched  taken.  alarm.  into  minutes)  and  were  disturbance  experiments  and  2  meters  movements  in  Activity  in  the  fish  when  The g  fish  i n each tank were fed meals of chopped h e r r i n g (50  per f i s h ) .  Meal frequency was a l t e r e d t o simulate  feeding o p o r t u n i t i e s . every 7 days,  Meal f r e q u e n c i e s  3) every 14 days,  of f i s h s t a r v e d  were: 1) every 4 days, 2)  and a r e p l i c a t e d c o n t r o l s e r i e s  f o r 8 weeks a f t e r the f i r s t meal.  meals was the same as i n chapter  different  The number of  2 ( F i g . 3.2).  3.2 RESULTS: Before starved  for  monitored  feeding  counts  3.2)  increased every  activity  weeks.  taken  illustrate  excretion.  fed  three  individual  from the f i r s t  Activity  (Fig.  beginning  experiments  Their  activity  was  feeding t o the end of from the f i r s t  a l l fish  to the  a p e r i o d of a c c l i m a t i o n i n  continuously  the  experiment.  third  or  spontaneous  swimming a c t i v i t y  i n a l l treatments a t an equal two  weeks reached a p l a t e a u  counts per day by t h e i r t h i r d  fourth  activity  s i m i l a r to those f o r oxygen consumption and Initially,  were  levels ammonia  gradually  rate  (per f e e d i n g ) .  Fish  of  approximately  1100  feeding  (i.e.  6  weeks).  T h i s l e v e l d i d 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. fed  The d a i l y spontaneous a c t i v i t y of the  every four and seven days continued  more v a r i a b l e .  By the f i f t h  feeding  t o i n c r e a s e and  fish  become  ( i . e . 5 weeks), the f i s h fed  every seven days reached a p l a t e a u of 1761 counts per day whereas the  f i s h fed every four days  day  a f t e r 3 weeks ( F i g . 3.2).  recorded  D i s c u s s i o n of the metabolic requires  defining  when  an average 2134 counts per  parameters i n r e l a t i o n t o r a t i o n  a c c l i m a t i o n has occurred  45  so  that  only  2800  LU to  2400-  +1  a  2000-  or LU a. to  1600  • 11-  o o  1200  < 2 < LU  FEEDING INTERVAL O 14 DAYS N= 14 • 7 DAYS N=7 * 4 DAYS N=4  800 0+  400  3  4  5  6  7  8  9  10 11 12  FEEDING NUMBER  F i g u r e 3.2. Average d a i l y a c t i v i t y counts f o r the 14, 7, and 4 day feeding intervals from the f i r s t feeding until the experiments ended. 46  post-acclimation observed, daily  are a n a l y z e d .  the  reach  final  ration  of each treatment.  asymptotes first  effect  in Fig.  3.2.  A  The counts per day  which can be c o n s i d e r e d the a c c l i m a t e d  feedings.  acclimation each  3.1  gives  the  treatment.  In the  feedings  discussion  Interval  for  Pre-acclimation Feedings  Post-acclimation 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  1, 2  3, 4, 5, 6, 7  Because an  an i n c r e a s e i n d a i l y counts c o u l d be caused  increase  activity  at  tailbeat experiment.  i n swimming v e l o c i t y or by  constant  frequencies No  velocity, in  P(F  observations  47  made  throughout between  of of the days  group (P(F = 0.51) > 0.25, DF  P(F = 0.77) > 0.25,  = 1.21) > 0.25,  either  periods  were  s i g n i f i c a n t d i f f e r e n c e was found  3,24 - 4 day i n t e r v a l ;  interval;  longer  a l l treatments  p o s t - p r a n d i a l w i t h i n each treatment =  of  e f f e c t s , only p o s t - a c c l i m a t i o n data were c o n s i d e r e d .  14 days  by  in  of p r e -  Table 3.1. D e f i n i t i o n of pre and p o s t - a c c l i m a t i o n feedings d a i l y a c t i v i t y count data i n the three r a t i o n treatments. Feeding  have  values  number  following  state. to  feedings and the number of p o s t - a c c l i m a t i o n ration  treatment  Table  from  eventually  was t h a t which gave both g r e a t e r and l e s s e r  subsequent  gradual  feedings  f e e d i n g a t which a c c l i m a t i o n was considered  occurred  is  The e f f e c t of a c c l i m a t i o n on the mean  i n counts per day occurs with c o n s e c u t i v e  the beginning  for  where  a c t i v i t y counts can be observed  increase  The  values,  DF = 13,56 - 14  DF = 6,28 - 7 day day  interval).  Similarly,  when  the  results  f o r a l l days  pooled to g i v e a mean f o r each treatment treatments  compared,  frequency the  average  effect of  was  (Fig.  activity  found  group and the  significant difference  (P(F = 0.95)  > 0.25,  3.2), or  estimate  but t a i l b e a t  was  beat  Because  a  treatment  frequency d i d not, the d u r a t i o n  number of a c t i v i t y bouts per u n i t time  were  a  l e v e l , but not the swimming v e l o c i t y . a c t i v i t y energy  the sum  metabolic r a t e s ( F i g . estimate and  tail  DF = 2,130).  expenditure,  both the  consumption and a c t i v i t y of the f i s h were recorded. consumption  were  different  in  d a i l y number of a c t i v i t y counts showed  f u n c t i o n of r a t i o n To  no  post-prandial  of  3.3).  activity,  digestive  I t was,  therefore,  oxygen  T o t a l oxygen and  standard  necessary  to  s u b t r a c t standard and d i g e s t i v e metabolism from the  t o t a l to c a l c u l a t e the a c t i v i t y component of metabolism. The obtained  sum  of the d i g e s t i v e and standard metabolic r a t e s  by r e g r e s s i n g the a c t i v i t y counts per day  corresponding oxygen consumptions examination each  was  treatment,  ( F i g . 3.4,  made s e p a r a t e l y f o r each day  3.5,  against  and  3.6).  not  This  g r a d u a l l y d i m i n i s h e d to zero s e v e r a l days f o l l o w i n g a  The  oxygen consumption i n t e r c e p t of each r e g r e s s i o n  the  combined  made d i g e s t i n g  in  constant,  but  expenditure  the  post-prandial,  because d i g e s t i v e metabolism was  energy  was  meal.  represented food  and  on  standard metabolism ( i . e . a c t i v i t y equals 0 a t the Y - i n t e r c e p t ) . After  digestion  finished,  the i n t e r c e p t became  constant  r e p r e s e n t e d the standard metabolic r a t e o n l y (Line 4, L i n e 4, F i g . 3.5, and  each  Fig.  and 3.4;  and L i n e 7, F i g 3.6). For each r a t i o n  treatment  day p o s t - p r a n d i a l the combined d i g e s t i v e and  standard  48  100  10'  U  t  1  2  l  l  3  l  4  5  l  t  l  l  l  l  l  l  l  l  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) f o r sablefish, each day p o s t - p r a n d i a l , when a c c l i m a t e d t o i d e n t i c a l meals f e d every 4, 7, and 14 days. 49  100  1000 2000 ACTIVITY COUNTS PER DAY  Figure 3.4. Regressions of oxygen consumption counts over the d i g e s t i v e p e r i o d f o r s a b l e f i s h meals every 4 days. 50  300C  and activity acclimated to  1001  —I  —  1000 ACTIVITY  1 2000  COUNTS  ' 3000  P E RDAY  Figure 3.5. Regressions of oxygen consumption and a c t i v i t y counts over the d i g e s t i v e p e r i o d and afterward for sablefish a c c l i m a t e d to meals every 7 days. The r e g r e s s i o n s f o r days 4 to 7 p o s t - p r a n d i a l are i d e n t i c a l and pooled. 51  80  Figure 3.6. Regressions of oxygen consumption and activity counts over the d i g e s t i v e p e r i o d f o r s a b l e f i s h acclimated to meals every 14 days. The r e g r e s s i o n s f o r days 7 to 14 have been pooled as d i g e s t i o n was complete. Also included i s the r e g r e s s i o n f o r the l a s t month of o b s e r v a t i o n s on s t a r v e d f i s h . 52  metabolic  r a t e s are  in  figure  this  intercepts had  a  (Fig.  illustrated  were  the standard  3.4,  3.5,  considerably  p r a n d i a l than f i s h were s i m i l a r . (Fig.  and  fed every four and  the  activity  examining  the  with time s i n c e feeding  (Table  every four and  7 day  was  the case f o r the a  feeding  estimated  activity  given  levels  seven days demonstrated t h a t  only two credible  data S.E.  changed  f i s h fed every two  the  weeks.  mean  =  6,28  No  These  fish  tenth  day  (Table  feeding,  variation.  the  T h i s , however,  a c t i v i t y u n t i l the  first  of  post-prandial  3.2).  showed  low  values  were  f i s h p r i o r to 20 days p o s t - p r a n d i a l because  p o i n t s were a v a i l a b l e f o r each day and could  whether  P(F = 0.864) = 0.534, DF  with c o n s i d e r a b l e  f o r the s t a r v e d  metabolism  treatment,  intervals respectively).  each  3.8).  A n a l y s i s of v a r i a n c e  s t a r v e d a f t e r the  turn  for  (Fig.  p o s t - p r a n d i a l a f t e r which a marked decrease occurred  activity  post-  which i n  metabolism  w i t h i n each 3.2).  weeks  day  of i n t e r e s t to c o n s i d e r  r e l a t i v e l y constant  Control f i s h ,  regression  given  counts per day were the same on a l l days  for 4 and  displayed  the  from t o t a l metabolism  differences in  (P(F = 0.173) = 0.932, DF = 3,24;  not  of  errors  F i s h fed every two  of  p o s t - p r a n d i a l was  the mean d a i l y a c t i v i t y counts,  activity  standard  seven days,  component  between r a t i o n treatments, i t was  fed  3.6).  The  lower combined r a t e on any  treatment i n each day  fish  errors  By s u b t r a c t i n g these values  3.3),  Before  i n F i g . 3.7.  be computed.  The  two-point  therefore means  no  were,  however, s i m i l a r to those a f t e r 20 days p o s t - p r a n d i a l . The the  a c t i v i t y component of t o t a l metabolism,  d i f f e r e n c e between t o t a l metabolism ( F i g 3.2)  d i g e s t i v e and  standard  metabolism ( F i g . 53  3.7),  calculated  as  and  of  the sum  is illustrated  for  100  90-  801  70-  g  _i o  6 0  '  < u. 501 2£  Lo 40' 30'  F E E D I N G INTERVAL O • •  20 < 3  4 DAYS 7 DAYS 14 DAYS  n=7 n=5 n=5  10H  »  V  4  5 DAYS  I  6  I  |  7  l  8  l  9  l  t  |  l  l  10 11 12 13 14 15  POST-PRANDIAL  Figure 3.7. Standard and d i g e s t i v e metabolism of sablefish a c c l i m a t e d t o meals every 4, 7, and 14 days over the between meal period. Data p o i n t s are the i n t e r c e p t s of r e g r e s s i o n l i n e s i n Fig. 3.4-3.6 with the S.E. of the i n t e r c e p t . Sample s i z e s (n) are the number of p o i n t s used i n the r e g r e s s i o n . 54  15' FEEDING INTERVAL O U DAYS • 7 DAYS • H DAYS  U13' 12' „ 11 or  \  Q.  o  to  o  <£ 6i LU  s  51  >t= 4i  2' 1. 5 6 7 8 9 10 11 12 13 U 15 DAYS POST-PRANDIAL  F i g u r e 3.8. A c t i v i t y component of t o t a l metabolism i n s a b l e f i s h a c c l i m a t e d t o meals every 4, 7, and 14 days over the between meal period. Data p o i n t s represent the d i f f e r e n c e between p o i n t s i n F i g . 3.3 and 3.7. 55  Table 3.2. Mean a c t i v i t y counts per day f o r each day p o s t prandial i n the three r a t i o n treatments and f o r days 20-52 postprandial for starved f i s h . Days P o s t Prandial  Mean A c t i v i t y Counts per Day (+_ S.E.) Feeding 4 days (n = 7)  1 2 3 4 5 6 7 8 9 10 11 12 13 14 20 22 24 26 28 30 32 34 40 44 48 52 each  2192 2158 2145 2041  -  7 days (n= 5)  (64) (214) (147) (164)  1803 1591 2063 1636 1973 1772 1506  -  ration  treatment  in Fig.  counts per day p o s t - p r a n d i a l , every  14  days,  metabolism points ration,  Interval  was r e f l e c t e d  14 days (n = 5)  1213 1263 1050 1270 1300 1111 1217 1126 1578 1327 911 752 487 795  (231) (285) (275) (137) (107) (178) (250)  -  -  -  -  3.8.  observed  The d e c l i n e  calculated  expressed  i n the d i s t r i b u t i o n  in  (102) (223) (152) (101) (64) (189) (281) (285) (124) (224) (170) (130)  activity  of  activity  I f the means of these  f o r each treatment and  i n conventional d a i l y units  56  531 791 482 223 996 545 1078 661 701 814 600 290  i n Table 3.2 f o r f i s h fed  measurements between f e e d i n g s .  were  (49) (157) (173) (131) (164) (62) (156) (163) (201) (141) (128) (150) (133) (204)  Starved  plotted (Fig.  against  3.9), i t i s  121  "1  0.2  I  •  r  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 s a b l e f i s h ^ a b o l i s m when s t a r v e d and when a c c l i m a t e d t o meals every 4, 7, and 14 days as a lunctton of r a t i o n expressed on a d a i l y b a s i s . Means are from the data i n F i g . 3.8. 57  apparent  t h a t r a t i o n d i r e c t l y i n f l u e n c e d the l e v e l of  Also  in  t h i s f i g u r e were estimates f o r the s t a r v e d  were  not i n c l u d e d i n F i g .  3.8  activity. fish  as they g i v e an unwieldy  which abcissa  ( i . e . up t o 52 days p o s t p r a n d i a l ) . Of  note was  devoted was  the p r o p o r t i o n of t o t a l metabolism  to a c t i v i t y  less  than  ( F i g . 3.9).  20% of the  (Fig.  3.3)  In a l l cases a c t i v i t y metabolism  average  hourly  expenditure.  This  occurred d e s p i t e o b s e r v a t i o n s t h a t the f i s h were g e n e r a l l y a c t i v e throughout  the day,  the tank bottom.  spending  The  relatively l i t t l e  f i s h were,  however,  time r e s t i n g  on  diurnally active  and  showed  only s l i g h t nocturnal  activity.  hourly  oxygen consumption was  measured as a 24 hour average  the  photoperiod  while  the  fish  illustrated The  was  the a c t i v i t y energy  were a c t u a l l y swimming  in F i g .  standard  12 hours,  Consequently,  was  because and  expenditure  about  twice  that  3.9. metabolic  rate  rate  the oxygen consumption i n t e r c e p t of the lowest l i n e  no  longer  appeared  contributed  considered  (Fig.  to  3.10)  constant  The standard  measured a f t e r d i g e s t i o n was total  metabolism.  to e x e r t a s t r o n g c o n t r o l l i n g  metabolism  Standard  3.6.  also  from F i g s . 3.4,  these f i g u r e s which was  and  could  estimated was  3.5,  of the f i s h  given  one  fish  size  over  ration standard  and  usually  temperature.  metabolic r a t e c o n s t i t u t e d a much l a r g e r p r o p o r t i o n  of  expenditures.  Estimates of r o u t i n e metabolic r a t e ( F i g .  3.11)  were simply  of a c t i v i t y and standard metabolism or the average  metabolism a f t e r d i g e s t i o n had stopped 58  in  complete and  d e s p i t e the f a c t t h a t t h i s was  the t o t a l metabolism than a c t i v i t y  the sum  metabolic  Again,  influence  be  ( F i g . 3.2).  The  total  e f f e c t of  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 s t a r v e d f i s h as a f u n c t i o n of ration expressed on a d a i l y b a s i s . Means are based on the i n t e r c e p t s of p o s t - d i g e s t i v e r e g r e s s i o n s i n F i g . 3.4 - 3.6. Data for s t a r v e d f i s h are f o r days 20 - 52 p o s t - p r a n d i a l ( F i g . 3.6). 59  F i g u r e 3.11. Routine metabolism of s a b l e f i s h a c c l i m a t e d to meals every 4, 7, and 14 days and s t a r v e d f i s h as a f u n c t i o n of r a t i o n expressed on a d a i l y b a s i s . Means are based on the sum of data p o i n t s used t o estimate the means presented i n F i g . 3.9 and 3.10. 60  ration  on  observed  the for  r o u t i n e metabolic r a t e i s of the a c t i v i t y and  3.3  metabolism,  form  as  although  the  The t h e o r e t i c a l swimming energy expenditures of p e l a g i c  fish  c u r v a t u r e of the l i n e  standard  same  i s r e l a t i v e l y greater.  DISCUSSION:  have been examined by Ware (1975,  1978).  He suggests two  levels  of  1) c r u i s i n g speed which  gives  a c t i v i t y may  the  greatest  which  optimize growth:  d i s t a n c e per u n i t energy,  and 2)  g i v e s the g r e a t e s t net energy g a i n .  foraging latter  includes  not o n l y v a r i a b l e s f o r the swimming energy e x p e n d i t u r e ,  but a l s o  the  prey  concentration.  distinctions  to  is  difficult  s a b l e f i s h which have  l a r g e prey items i n f r e q u e n t l y time  It  The  speed  been  to  apply  reported  these  consuming  ( S u l l i v a n and Smith 1982).  Is the  spent s e a r c h i n g between meals best d e s c r i b e d as c r u i s i n g or  foraging? density  From  Ware's  decreases,  converge.  the  a n a l y s i s i t i s apparent optimal  c r u i s i n g and  that  as  foraging  prey speeds  Consequently there i s l i k e l y l i t t l e d i f f e r e n c e between  these values f o r i n f r e q u e n t l y fed s a b l e f i s h . The  lack  of  difference in t a i l  beat  frequencies,  between  days p o s t - p r a n d i a l w i t h i n r a t i o n treatments  ration  treatments,  experiments  moved  frequencies  were  tunnel applied these  indicates at  that  a constant  speed.  sablefish Although  between in  these  tail  beat  recorded f o r d i f f e r e n t known v e l o c i t i e s  r e s p i r o m e t e r ( F u r n e l l 1987), to  the  or  s a b l e f i s h swimming i n the  in  these v e l o c i t i e s cannot mass  respirometers.  l a r g e tanks the f i s h swam with a b u r s t and g l i d e  in the swimming t u n n e l the f i s h used a steady t a i l  61  either  beat.  a be In  pattern; Burst  and  glide  swimming  is  swimming (Weihs 1974,  Blake 1983).  estimate swimming speed frequencies  or r e l a t e  It  efficient  than  I t i s t h e r e f o r e impossible to  i n the mass r e s p i r o m e t e r s from t a i l  It i s ,  that  sablefish  pursuing a s i n g l e , varied This  activity  beat  however, s i g n i f i c a n t that the  f r e q u e n c i e s were the same i n a l l treatments a t appears  steady  i t to c o r r e s p o n d i n g energy expenditures i n  the swimming t u n n e l . beat  up t o 50% more  perhaps periods  i n the  different  all  tail  times.  treatments  were  optimal c r u i s i n g speed and t h a t  they  to change t h e i r  energy  would suggest that i n the presence of more  expenditures. abundant  food,  s a b l e f i s h have evolved t o b e n e f i t from more p e r s i s t e n t s e a r c h i n g , but of  a t a speed which g i v e s the g r e a t e s t d i s t a n c e or prey encounter The  over days,  (i.e.  counts per day) d i d not d i f f e r  f e e d i n g i n t e r v a l f o r the f i s h fed once every 4  but  those  a c t i v i t y toward This  f o r the energy expended.  l e v e l of a c t i v i t y  the  probability  fed  every 14 days  displayed  the end of the i n t e r v a l  (Table  a  decrease  3.2,  Fig.  f u r t h e r 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  between  treatments.  r e s u l t s presented i n chapter 2 i n d i c a t e that f i s h  two  weeks  had a s l i g h t l y p o s i t i v e energy balance  energy balance may  in  observed  t o conserve l i m i t e d energy  The  7  3.8).  The d e c l i n e of a c t i v i t y i n f i s h fed  two weeks suggests an attempt  Their  and  every stores.  fed  every  (Table  2.1).  have been negative had they not reduced  a c t i v i t y d u r i n g the l a t t e r part of the two week f e e d i n g i n t e r v a l . Much existence  theoretical  has  been  given  of a r e l a t i o n s h i p between a c t i v i t y and r a t i o n  (Kerr 1971a, Majkowski  consideration  and  1971b,  1971c,  Waiwood  Ware 1972,  1981).  1975,  1978,  Kerr (1982) suggested 62  to  the  in  fish  Jones a  1978, direct  proportionality  between  food  intake and  activity  expenditures.  Ware (1978) hypothesized a r e l a t i o n s h i p between prey d e n s i t y swimming there  speed as  implied by Jones (1978).  i s an assumption of f a i r l y constant  (1975)  estimated  Ivlev's  (1960)  suggested constant  the  in  as  suggested  as have r a t e s as low as 1.5  activity  their activity routine than  high  activity  standard  the day,  for a c t i v i t y  times standard  More importantly,  and  r a t e when w e l l fed  considerably  2 4 hours ( F i g 3.3  should,  noted  be  difficult  to  that  and  have  been  metabolism of  the  modulating the average  of  not  more  fish  are  most  3.7).  These  Poorly  those i n the w i l d .  sablefish  were by no means i n a c t i v e .  a c t i v e l y swimming the m a j o r i t y  active  rate.  and low  might be a t t r i b u t e d to the d i f f e r e n c e between i n c a p t i v i t y and  when  was  l e s s when p o o r l y fed  spontaneously a c t i v e f i s h  beat f r e q u e n c i e s .  rate  of  (1956)  metabolic  metabolism i s on the order  i s averaged over  respirometers  Winberg  i s the s a b l e f i s h ' s primary means of  energy expenditure.  however,  reanalysis  experiments i n d i c a t e that c o n t r o l  times the standard  active during  a  four times the standard  post-digestive  1.4  values  as  These  period  in  although Ware  r o u t i n e energy expenditure of w i l d f i s h  approximately twice the  1978).  activity,  Alburnus.  Esitmates  (Ware  In these approaches  p e r i o d of a c t i v i t y  data on f o r a g i n g  that at  the  and  The  in  the  w e l l fed f i s h were  frequently,  were i n d i s t i n g u i s h a b l e from w e l l fed f i s h . b e l i e v e that  w e l l fed w i l d f i s h could  more f r e q u e n t l y than w e l l fed experimental f i s h unless also active a l l night.  mass  of the time when observed for  fed f i s h r e s t e d more  It  be they  It  tail but is  active were  I t i s p o s s i b l e t h a t w i l d f i s h swim f a s t e r  63  giving  routine  T h i s would, speed  to standard metabolic r a t e r a t i o s of 2 or  however,  not be i n agreement with optimal  t h e o r y nor the constant swimming speeds observed  experiments.  Thus,  nature  as much energy swimming as c a p t i v e f i s h  spend  mass r e s p i r o m e t e r s The rate  it  between r a t i o n and the r o u t i n e  state  the  2 ( F i g 3.11).  metabolism has a near  ( F i g 3.9)  as proposed  level  of  The  by Kerr  linear relationship  (1982).  c i r c u l a t i n g and c e l l u l a r m e t a b o l i t e s ,  sablefish  (as standard metabolism i s d e f i n e d ) i s a  metabolism  metabolic  however,  useful  ration  circulating  and in  to the  post-  function  of  the  temperature  on  i s r e q u i r e d f o r comparison.  They  i n an e c o l o g i c a l context without  some  g i v e n to what c o n s t i t u t e s a standard r a t e .  I t i s apparent  ( F i g 3.7),  state,  with  r a t e s are u s e f u l f o r i n v e s t i g a t i n g  r e s u l t s r a i s e the q u e s t i o n ; state?  3.10).  history.  where some standard  consideration  two  p o s t - d i g e s t i v e metabolic r a t e of  of e x t e r n a l v a r i a b l e s such as weight and  are not,  the  (Fig.  even  fish.  Standard  The r e s t i n g ,  rate  I t i s not unreasonable  digestive  effect  metabolic  r e l a t i o n s h i p between standard metabolic r a t e  long term r a t i o n  in  large  routine  i n the standard r a t e  Activity  a  in  a c t i v i t y and standard components and  system i s most obvious  expect  these  form t h a t the m e t a b o l i t e p r o c e s s i n g  showed i n chapter  of  in  i s e n t i r e l y possible that s a b l e f i s h  has the same, two-state  consists  swimming  (Jones 1978).  relationship  information  more.  when i s a f i s h  These  in a post-absorptive  when the primary process of d i g e s t i o n ends  but not when the b i o c h e m i c a l consequences of e l e v a t e d metabolites  i f ever.  and probably hormones  The d i f f e r e n c e 64  reach  a  steady  i n the standard metabolic r a t e s  of  w e l l and  tissue  p o o r l y fed f i s h may  turnover  metabolism).  The  d i g e s t i v e metabolic further  argues  r e f l e c t a d i f f e r e n c e i n r a t e s of  (i.e.  combined  catabolic  gradual  d e c l i n e of the combined standard  r a t e s , i n f i s h fed every two  the  d i f f i c u l t y of  defining  a  and  anabolic  weeks ( F i g  and 3.7),  post-absorptive  state. In total  summary,  i t i s apparent t h a t the a c t i v i t y component  metabolism may  p l a y a much l e s s s i g n i f i c a n t p a r t  budgeting than p r e v i o u s l y thought and Further, situations  standard and  t o t a l metabolic  metabolism  expenditure.  i n energy  i t i s a f u n c t i o n of r a t i o n .  i s not constant  can represent  of  all  feeding  a l a r g e p r o p o r t i o n of the  fishes  The  modeling of s a b l e f i s h e n e r g e t i c s  65  in  impact of these f i n d i n g s on i s considerable.  the  CHAPTER 4: PARTITIONING OF LOCOMOTOR AND FEEDING METABOLISM IN SABLEFISH 4.0 INTRODUCTION: It  i s widely  recognized t h a t the  f i s h e s can be separated  aerobic  metabolism  of  i n t o three g e n e r a l components:  R = Rs + Rd + Ra ( B r e t t and Groves 1979, Priede 1985) where R i s t o t a l metabolism  (mg oxygen/kg/hr).  metabolism  ( R s ) , the  The minimum l e v e l of r e s p i r a t o r y  standard metabolic r a t e ,  consumption of a r e s t i n g , unfed, u n s t r e s s e d upper  limit  (Brett  limits  is  periods cannot  fish  is  the  the  and Groves 1979). fish's  metabolic  of  The d i f f e r e n c e between scope  ( F r y 1947).  g r e a t e r than the metabolic scope can occur  when a n e r o b i c metabolism i s used, usually  be  maintained  however,  f o r long and an  oxygen  ( F r y 1947).  i s d e f i n e d as the maximum s u s t a i n e d r a t e  uptake  production  respiratory  The  oxygen these Energy  for short this  oxygen  state  debt  is  g e n e r a l l y made up a f t e r w a r d . The  term SDA (Rd) has a p l e t h o r a of f u n c t i o n s a s c r i b e d to i t  (Muir and N i i m i 1972,  Beamish 1974,  Tandler and Beamish 1979). who  concluded  biochemical  K l e i b e r 1975,  These a r e reviewed  of  of  m e t a b o l i t e s and  protein.  Regardless  elevation  of oxygen consumption immediately  i t s cause,  c o n t i n u i n g f o r v a r i o u s p e r i o d s of time. oxygen  by J o b l i n g (1981)  t h a t the m a j o r i t y of SDA energy  degradation  SDA  B r e t t 1976,  is the  is  expended  on  synthesis  of  observed  as  an  f o l l o w i n g a meal and  The t o t a l e l e v a t i o n  of  consumption and the d u r a t i o n of the e f f e c t are c o r r e l a t e d  66  with  ration  size,  temperature Davenport maximum  (Saunders 1979,  (especially  1963,  Muir  and  protein Niimi  J o b l i n g and Davies 1980).  content)  1972,  and  Vahl  and  In most f i s h e s  the  l e v e l of SDA i s between 1.5 and 2.5 times  metabolic r a t e large  quality  the  standard  ( J o b l i n g 1981) and i n some s p e c i e s can r e p r e s e n t a  proportion  of the metabolic scope  (Soofiani  and  Hawkins  1982). Activity  metabolism can account f o r a l l the metabolic scope  i n many s p e c i e s ( B r e t t 1964, it  B r e t t and Groves  i n others ( S o o f i a n i and P r i e d e 1985).  with  1979) and most  C l e a r l y , f i s h are faced  a budgeting problem when the demands from SDA and  exceed  the  allocation proposed these  a e r o b i c metabolic scope mechanisms  such as f e e d i n g then  opportunistic  circumstances permit. f o l l o w i n g a meal, physiological locomotion. possible  (Priede  i n nature and can  Faced with a need  Behavioral  resting  have  mechanism The  allocating  objective  1979),  only  been  however,  operate  for activity  i t would be advantageous  activity  1985).  f o r some s p e c i e s (Vahl and Davenport  are  of  when  immediately  f o r a f i s h to have a  aerobic  of t h i s study was  metabolism to  e x i s t e n c e of such a mechanism by imposing  examine  to the  simultaneous  SDA and swimming m e t a b o l i c l o a d s .  4.1 METHODS: To d e f i n e the d u r a t i o n of SDA, =  0.993  kg  +  0.012 S.E.  f i v e preweighed  N = 10) were  placed  s a b l e f i s h ("X  in  each  mass  respirometer and held a t t h e i r p r e s c r i b e d a c c l i m a t i o n  temperature  and  of  chopped  the  plastic  photoperiod.  herring  per  fish.  They  were fed weekly with 50  To determine m e t a b o l i c 67  rate,  g  covers  were p l a c e d over the tanks,  heat exchangers the  engaged.  Oxygen consumption  d i f f e r e n c e between an i n i t i a l  hours  later.  (Indophenol exceed  method,  This  marine  ppm is  fishes  i n these  was  determined  oxygen sample and  24  S t r i c k l a n d and Parsons 1972);  they d i d not  t o t a l ammonia and were u s u a l l y l e s s below a l e v e l c o n s i d e r e d  (Haywood 1983)  chronically  than  0.1  toxic  in  and no t o x i c symptoms were observed  experiments.  establish  the  standard  three f i s h were t e s t e d Brett  (1964)  Initially, to  from  another  To impose the dual metabolic load of a c t i v i t y and SDA  by  and  Ammonia c o n c e n t r a t i o n s were synchronously monitored  0.46  ppm.  the water flow c u r t a i l e d  metabolic r a t e i n the  classic  i n the same t u n n e l r e s p i r o m e t e r  a t a l l but the e a r l i e s t  and to  described  of  digestion.  i n the swimming t u n n e l experiments, a f t e r  acclimation  weekly meals,  post-digestive  each f i s h was  state),  stage  manner,  s t a r v e d f o r 300 hr (to ensure  anesthetized  (2-phenoxy  ethanol)  a and  weighed, p l a c e d i n the r e s p i r o m e t e r , and allowed to a c c l i m a t e f o r 24 hours.  I t s oxygen consumption  was  hour runs a t d i f f e r e n t swimming speeds. made f o r i n a c t i v e f i s h . a  swim  often  bladder,  rest  on  velocities observed locomotor and Fish  T h i s was  Determinations were a l s o  p o s s i b l e because  sablefish  are consequently n e g a t i v e l y buoyant the  bottom of the  up to 15 cm/sec. continuously movement was  current  then measured i n o n e - h a l f -  stopped  were brought  and  tunnel  chamber  During these runs, the run r e s t a r t e d  observed.  for at l e a s t  if  and at  the f i s h the  will  current were  slightest  The r e s p i r o m e t e r was one-half-hour  lack  between  flushed runs.  up to the t e s t v e l o c i t y and held there f o r  68  15  min  before  the  water s u p p l y was c l o s e d and Data from these unfed  the  sample  taken.  f i s h ensured  oxygen  consumption f o r f i s h with o n l y the metabolic  first  oxygen  o b t a i n i n g the demands  of  swimming a c t i v i t y . Following fish  was  hours, The  runs,  each of the  g i v e n a 50 g meal of chopped h e r r i n g  anesthetized  based  on  allowed  18  the meal.  hours  the p o s s i b i l i t y of f i s h  C a l c u l a t i o n of oxygen consumption  to  acclimate  runs s t a r t e d  to  24 hours a f t e r  the  Every  was  fish  respirometer  feeding.  fish  f o r c e d t o swim a t four d i f f e r e n t  highest  was and  i n the  speeds,  one-half-hour, and i t s oxygen consumption determined. d e t e r m i n a t i o n s were a l s o made f o r the f i s h while  was  Each day f o r  s i x days ( i . e . 150 hr p o s t - p r a n d i a l ) the  respirometer  original  and, a f t e r s i x  the p r e - f e e d i n g weight of the f i s h .  experimental to  three  and t r a n s f e r r e d t o the t u n n e l r e s p i r o m e t e r .  s i x - h o u r d e l a y was intended to reduce  regurgitating  up  these i n i t i a l  for  As b e f o r e ,  inactive.  imposed swimming v e l o c i t y was s e l e c t e d on the  The  criterion  t h a t v e n t i l a t o r y r a t e r e t u r n e d t o the normal r e s t i n g s t a t e w i t h i n one  minute  of the run's end.  equivalent metabolic  to approximately rate.  consumption  rates  significantly  digestive  oxygen  consumption  Data facing  (15  - 120 from  state.  throughout  double  min  post-run)  t o be  sustained  post-run showed  well rested inactive  oxygen  them not fish  I t was t h e r e f o r e assumed  r a t e s represented a e r o b i c  from these experiments the  60 percent of the maximum  Subsequent monitoring of the  different  similar  T h i s was l a t e r determined  that a l l  metabolism  gave the oxygen consumption of  metabolic load of SDA  and  forced  in a  only. fish  activity  the d i g e s t i v e process and f o r a s h o r t time a f t e r w a r d .  69  4.2  RESULTS: Information  from  c o l l e c t e d before and the  previous  the  mass  respirometers  independently  4.1),  of t h a t f o r weekly fed f i s h i n of  SDA  (corresponding to a weekly 50 g meal of chopped h e r r i n g per  fish)  spanned  chapters,  (Fig.  approximately  demonstrated  4 days.  the  course  While i n the mass  respirometers  the f i s h swam s t e a d i l y and s l o w l y d u r i n g the day with a burst and glide  p a t t e r n showing a s l i g h t decrease  after  feeding.  12-hr  night.  Swimming a c t i v i t y was  i n swimming  immediately  g r e a t l y reduced  d u r i n g the  A n a l y s i s of v a r i a n c e i n d i c a t e d there was  a highly  s i g n i f i c a n t d i f f e r e n c e between mean oxygen consumption data broken hour  i n t o 20-hr p o s t - p r a n d i a l b l o c k s  The  20-  blocks were s e l e c t e d as they gave s i m i l a r sample s i z e s  for  each b l o c k . There was, means,  of  however, no s i g n i f i c a n t d i f f e r e n c e between  20-hr time b l o c k s ,  (0.10>P(F)>0.05).  (P(F)<0.0005).  when  The  grand  from 100  to 180  hr  post-prandial  mean of these l a s t four time  oxygen/kg/hr (+.0.81 S.E.  was  62.0  mg  as  the  24-hr r o u t i n e metabolic r a t e c o n s i s t i n g of standard  r o u t i n e swimming oxygen demands. was mg  observed  i n the f i r s t  oxygen/kg/hr (+.1.6 S.E.  oxygen  consumption  routine rate. exceeded such  t h i s can be  N=4).  f e e d i n g and was  and  89.4  Hence the maximum e l e v a t i o n of  was  approximately  1.4  I t i s l i k e l y t h a t the maximum oxygen  t h i s but was  taken  The maximum oxygen consumption  time block a f t e r  to SDA  and  times  the  consumption  of too s h o r t d u r a t i o n to be determined  in  large respirometers. The  1)  due  N=18)  blocks  r e s u l t s from the tunnel respirometer were intended  provide  operating  a comparison between the oxygen consumption of with  o n l y a locomotor 70  oxygen demand and  fish  to, fish  facing  0)  cn  o20 10  20  AO  60 80 100 120 Hours Post-prandial  140  160  180  Figure 4.1. Oxygen consumption of s a b l e f i s h i n a 4000 L mass respirometer a t 8.5 C f o l l o w i n g a 50 g meal of chopped herring. The activity component of metabolism i s the d i f f e r e n c e between the routine p o s t - p r a n d i a l r a t e of oxygen consumption and the standard r a t e . 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  metabolic  rate  to  respirometers. respirometer, data  have  The  with  duration  therefore  and  oxygen  been separated  fish  standard  in  the  mass  determined i n  the  mass  into  Swimming  two  categories:  i n f l u e n c e d by SDA from 24 to 100  2) n o n - d i g e s t i v e — f o r  hr  f i s h not i n f l u e n c e d  ( F i g . 4.2).  tunnel 1)  post-  by  SDA  For each c a t e g o r y a  r e g r e s s i o n was preformed using the n a t u r a l l o g a r i t h m of consumption  velocity plotted  obtained  of SDA,  from 101 t o 300 hr p o s t - p r a n d i a l separate  that  i n d i c a t e d when d i g e s t i o n ended.  digestive--for prandial  compare  a  as  the  as  dependent  variable  independent v a r i a b l e .  i n F i g . 4.2.  These  and are  swimming the  lines  S t a t i s t i c s f o r the two r e g r e s s i o n s a r e :  1) Non-digestive Ln  the  fish  (mg oxygen/kg/hr) = 3.395 ( v e l o c i t y (m/sec)) + 4.058  Zero v e l o c i t y i n t e r c e p t = 57.9 (52.5 - 63.8 = 95% C.I.) 2 r = 0.936 N = 38 2) D i g e s t i v e Ln  fish  (mg oxygen/kg/hr) = 2.685 ( v e l o c i t y (m/sec)) + 4.426  Zero v e l o c i t y i n t e r c e p t = 83.6 (78.2 - 89.4 = 95% C.I.) 2 r The  = 0.937 slopes  N = 43  of the two r e g r e s s i o n s  are h i g h l y  significantly  different  (P(t)<0.001) as are the i n t e r c e p t s (P(t)<0.001).  regression  l i n e s i n t e r s e c t a t an oxygen consumption r a t e of 335.8  mg/kg/hr one the  and a swimming v e l o c i t y of 0.518  body l e n g t h per s e c ) . oxygen  prandial  was  The standard  mg/kg/hr (+2.2  72  (approximately  metabolic r a t e , based on  consumption of i n a c t i v e f i s h 52.8  m/sec  The  S.E.  from 100-300 N=ll).  This  hr  postis  5.1  Figure 4.2. Oxygen consumption of s a b l e f i s h i n a tunnel respirometer a t 8.5 C. Open c i r c l e s r e p r e s e n t f i s h s t a r v e d f o r >100 hr ( n o n - d i g e s t i v e ) and dots r e p r e s e n t f i s h from 24-100 hr post-prandial (digestive). L i n e s A and B represent the n a t u r a l log linear regressions for non-digestive and d i g e s t i v e fish respectively. Zero v e l o c i t y data are g i v e n as means with one S.D. Data are f o r three f i s h and 81 separate d e t e r m i n a t i o n s . 73  mg/kg/hr l e s s than the zero v e l o c i t y oxygen consumption of  the  regression for non-digestive f i s h ,  estimated  in  chapter  respirometer metabolic  and  3  for f i s h  comparable  fed every week  probably a b e t t e r estimate of  standard  metabolic  rate  (52.8  superimposed on the mass respirometer data  that  the  mass  actual  mg/kg/hr)  standard  i n the mass r e s p i r o m e t e r s  mg/kg/hr,  represents  the  has  ( F i g . 4.1).  s u b t r a c t e d from the r o u t i n e metabolic r a t e of  fish  in  to  rate.  The  is  intercept  been  When t h i s  post-digestive  (62 mg/kg/hr) the d i f f e r e n c e ,  oxygen  consumption  due  to  9.2  routine  swimming a c t i v i t y over 24 hr and agrees w e l l with the r e s u l t s chapter 3.  in  As the f i s h were r e l a t i v e l y i n a c t i v e d u r i n g the 12 hr  of darkness,  little  energy was  expended swimming.  consumption  while  spontaneously  double  24-hr  activity  the  swimming i s  metabolic  Hence, oxygen  likely  component  or  closer  to  about  18  mg/kg/hr.  4.3  DISCUSSION: One  the  of  the most noteworthy f i n d i n g s of t h i s experiment  intersection  of  velocity  curves  for  sablefish  (Fig.  4.2).  the  oxygen  digestive If  consumption compared  versus  with  Rd and Ra were  is  swimming  non-digestive  additive  over  the  metabolic scope of s a b l e f i s h , no i n t e r s e c t i o n would occur and lines  would be c l e a r l y d i s t i n g u i s h a b l e .  consumption was of  the  equal,  two  consumption  is,  when  p l o t t e d a g a i n s t swimming v e l o c i t y , the  r e g r e s s i o n s would d i f f e r ,  giving  That  identical corresponding  but the s l o p e s  the  average  SDA.  oxygen  intercepts would  curves separated by a constant to  the  In  be  oxygen these  experiments, the r e g r e s s i o n s f o r n o n - d i g e s t i v e and d i g e s t i v e 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 d e t e r m i n a t i o n a  swimming  The  scope. the  N=5)  fish  used  swimming  body lengths per sec ( B r e t t , unpublished in  these experiments,  this  corresponds  power preformance  curves f a l l s w i t h i n t h i s  a  seems  digestive  i t would not be p o s s i b l e f o r a r o u t i n e l y a c t i v e i t s food.  routine  activity  as  be argued t h a t i f swimming metabolism reduced  a c t i v i t y metabolism  digestion  data  it  velocity.  digest  under  actually  taken much beyond the i n t e r s e c t i o n  metabolism, to  and  range,  Although  t h i s cannot be r e f u t e d by the present  one datum was may  rate  velocities  non-digestive f i s h  higher oxygen demand than d i g e s t i v e f i s h . unlikely,  a  rate.  i n t e r s e c t i o n of these curves i m p l i e s that a t  g r e a t e r than the i n t e r s e c t i o n p o i n t ,  (+  to  C l e a r l y , the i n t e r s e c t i o n of the d i g e s t i v e  o c c u r r i n g a t 57% of the a c t i v e oxygen consumption The  at  data).  v e l o c i t y of 0.685 m/sec and an oxygen consumption  non-digestive  only  to  examined corresponds t o a v e l o c i t y of 1.37  of 592 mg/kg/hr.  have  allocated  The a c t i v e metabolic r a t e f o r s i m i l a r s i z e s a b l e f i s h  S.E.  For  the p r o p o r t i o n  decreases u n t i l swimming consumes a l l of the metabolic  temperatures  0.07  i n both  i n t e r s e c t i o n of these l i n e s would suggest t h a t as  oxygen demand i n c r e a s e s ,  digestion  It  indicating  l o g l i n e a r r e l a t i o n s h i p e x p l a i n e d 94% of the v a r i a t i o n  data s e t s .  fish  however,  ( F i g 3.9 and  conditions,  could was  I t must,  occur  required,  4.1)  be noted that  i s v e r y low.  both normal  synchronously.  swimming When  experiments with largemouth bass  75  routine  Consequently, activity  greater  d i g e s t i o n would d i m i n i s h .  fish  In  and  swimming similar  ( M i c r o p t e r u s s a l m o i d e s ) , Beamish  (1974;  F i g . 3) observed  no r e d u c t i o n i n SDA  as swimming v e l o c i t y  increased.  S a b l e f i s h are c o n s t a n t l y mobile,  p e l a g i c f i s h whereas  largemouth  bass  activity.  Perhaps such a s h u n t i n g mechanism i s r e q u i r e d only i n  species  which  are ambush predators with i r r e g u l a r  c o n s t a n t l y balance  the double  swimming and d i g e s t i o n w i t h i n t h e i r metabolic The  bursts  metabolic  load  of  of  scope.  i n d i c a t i o n of a p h y s i o l o g i c a l mechanism which  allocates  oxygen to swimming over d i g e s t i o n r a i s e s the q u e s t i o n of what the mechanism  may  be.  Studies by Daxboeck (1981) and R a n d a l l  Daxboeck (1982) suggest causes  a  stomach  r e d u c t i o n i n blood flow  leading  consequences The  of  to  the  liver,  this  reallocation  are  spleen,  unknown.  such a r e d i s t r i b u t i o n agree with  stomach and  metabolite catabolism, flow  to  gairdneri  while markedly i n c r e a s i n g i t to red muscle t i s s u e .  factors  here.  t h a t swimming a c t i v i t y i n Salmo  the  and  and The The  findings  l i v e r are the main s i t e s of d i g e s t i o n and respectively,  hence a r e d u c t i o n i n blood  c o u l d e a s i l y l i m i t the oxygen consumption  attributable  to  digestion. In summary, i t appears t h a t a p h y s i o l o g i c a l mechanism e x i s t s whereby  sablefish  locomotion locomotion  when  are able to a l l o c a t e t h e i r oxygen the  oxygen  demand  exceeds a t h r e s h o l d v a l u e .  76  from  both  supply  digestion  to and  CHAPTER 5: GENERAL DISCUSSION The  r e l a t i o n s h i p s between r a t i o n and a c t i v i t y metabolism and  r a t i o n and standard metabolic r a t e are ecological  and  existence never  d i r e c t t e s t s of them.  maintain  as  If f i s h ,  self sustaining  homeostasis  surprising which  perspectives.  Although  of these r e l a t i o n s h i p s had been suspected,  considered  in  a  direct  and other organisms, are  chemical  variable  limited supplies  return,  i s , however,  reactions  striving  environment,  t o consider  to  i t i s not mechanisms  i n t o areas y i e l d i n g the  e i t h e r through c o n s e r v a t i o n instructive  the  there were  t o f i n d p h y s i o l o g i c a l energy p a r t i t i o n i n g  sustaining It  physiological  of s i g n i f i c a n c e from both  or  greatest  expenditure.  the options t h a t  are  pursued and t h e i r consequences. It tanks  is to  impossible t o r e l a t e the a c t i v i t y  fish  i n nature.  It i s also currently  preform t h i s d e t a i l e d a n a l y s i s on w i l d experiments to  fish.  to  The tanks i n these  i n order that they might behave  when e x p r e s s i n g t h e i r a c t i v i t y .  i n the  impossible  were d e l i b e r a t e l y l a r g e and the f i s h w e l l  captivity  possible  observed  as  acclimated  naturally  For f i s h  as  in captivity  t h i s i s r e f e r r e d t o as spontaneous a c t i v i t y ,  however the term i s  somewhat  also  active, behavior captive same and  misleading. although  i n nature  i t i s usually  i s directed fish  Fish  i s not.  are  spontaneously  i m p l i c i t l y assumed  ( i . e . foraging Captive f i s h a r e ,  and escape) and  l i k e l y t o respond as w i l d  77  their  that  of  however, governed by the  p h y s i o l o g i c a l or b i o c h e m i c a l systems r e g u l a t i n g therefore  that  f i s h would,  wild  fish  within  the  l i m i t s of t h e i r c o n s t r a i n t , given s p e c i f i c The to  infrequent  permit  before  feedings  completion  stimuli.  i n these experiments were  of SDA  i n the  highest  a d m i n i s t r a t i o n of the next meal.  define  standard  metabolism).  metabolism  Sullivan  (i.e.  (1982)  and  selected  ration  T h i s was resting  treatment  necessary  to  post-absorptive  S u l l i v a n and  Smith  (1984)  demonstrated t h a t s a b l e f i s h could endure periods up to s i x months without  food  Further,  and  most  stomachs  sablefish  feeding  those experienced Assuming responding  to  partitioning  observed  the  of  Beamish  1983).  have  empty  Consequently, as not  sablefish  in  these  unlike  experiments  of  reflect  wild  the  sablefish  in  a v a r i e t y of  organisms.  natural  seeking  of brown t r o u t (Salmo  r o u t i n e metabolic  and  white  suckers  energy  food.  rate  feeding the  (1946c)  t r u t t a ) which had  (Catostomas  (Etienne of  activity  commersonii)  was  reduction  reduce a c t i v i t y when i n 1972). in  Callow the  r e s u l t s f o r the pulmonate gastropod Planozbis 78  been  s t a r v a t i o n more r a p i d l y than  Dragon f l y l a r v a e  reduced  been  reported  (Beamish 1964a) i l l u s t r a t i n g a  environments  A  r a t e of brook t r o u t ( S a l v e l l n u s  to d e c l i n e over short-term metabolic  Brown  were  mechanisms,  (1977)  Turbellarian  Dendrocoelum lacteum i n response to food d e p r i v a t i o n . similar  meals.  a c t i v i t y i n response to food d e p r i v a t i o n had  of swimming a c t i v i t y .  describes  and  strategy  The  poor  taken i n commercial t r a p s  measurements  starved.  standard  large  endogenous p h y s i o l o g i c a l c o n t r o l l i n g  behavior  observed  infrequent,  by w i l d s a b l e f i s h .  lethargic  fontinalis)  to  c o n d i t i o n s can be considered  that  metabolic  reduction  be adapted  (McFarlane  experimental  the  may  He  reports contortus  (Callow 1974).  When s t a r v e d ,  becomes l e t h a r g i c ,  the t u r t l e ,  s t e r n o t h a e r u s minor,  h a r d l y moving except to breath ( B e l k i n  1965).  Although the r e d u c t i o n of a c t i v i t y i n response to s t a r v a t i o n has been w e l l documented, ration  and  i t i s of c o n s i d e r a b l e importance  a c t i v i t y metabolism appear  relationship  (Fig.  2.9).  It i s d i f f i c u l t  the form of the curve i n F i g . standard (1982)  error  to have  2.9  a  dose-response  to be c o n f i d e n t that  i s sigmoid,  although the  of the p l o t t e d means supports t h i s  suggested t h i s type of r e l a t i o n s h i p with a  however,  his  work  was  that  based on p u b l i s h e d data  low  form.  Kerr  linear  form,  collected  for  d i f f e r e n t purposes with a c t i v i t y estimated by d i f f e r e n c e and with unknown  levels  relationship  of  error  indicates  (Solomon  and  Brafield  1972).  that s a b l e f i s h have evolved to  energy by m i n i m i z i n g a c t i v i t y  when faced with a low  This  conserve  probability  of prey capture i n a poor f e e d i n g environment.  S a b l e f i s h feed on  active,  also  motile  prey.  Reducing  a c t i v i t y may  reduce  p r o b a b i l i t y of prey encounter by d e c r e a s i n g the r e l a t i v e of  prey  and p r e d a t o r .  efficiency beyond  and  their  simulation  activity would  predator respective  model  Instructive  Assuming  to  might know  sensory  suggest  probability  that  ranges,  demonstrate  feeding  although there may  which a  this.  that s a b l e f i s h have  i n d i r e c t proportion to  velocity  natural s e l e c t i o n for  and prey movements  energy  are  random  random movement  However, evolved  it  to  reduction  of prey encounter with l e s s a c t i v i t y ,  is  modulate  opportunities.  be a  the  This in  the  i t i s of l e s s  s i g n i f i c a n c e than the r e s u l t i n g energy s a v i n g . This  partitioning  of  activity  79  in  proportion  to  food  availability  i s done a t a constant swimming speed.  demonstrated  both e m p i r i c a l l y and with hydrodynamics theory t h a t  f i s h have optimal swimming speeds ( B r e t t 1964, 1978,  Blake  parameter  1983).  being  These speeds may  optimized  1975),  and arguments  at  have  been  (Rosen 1967,  observed  any time p o s t - p r a n d i a l supports  because  to food supply,  periods  has  been  these  continuously  fish  must  Kerr 1971c,  parameter,  this.  It  means in  (Magnuson 1966)  and  for  activity prey  cannot  on  However,  hydrodynamic alter  and  activity  abundant  when prey i s s c a r c e appears to be the  sablefish  have  evolved  to  probably growth (Ware 1975).  optimize  be  energy  Having r e c e n t l y f e d ,  can b e n e f i t from the expenditure still  and  foraging  some  of a d d i t i o n a l  in i t s v i c i n i t y .  a  energy  S a b l e f i s h which  have  not  prey  to enter t h e i r area than swimming long d i s t a n c e s  every two  that  relation  (Magnuson 1969).  p e r i o d s of a c t i v i t y when prey i s more  seeking prey which may  f o r food.  The  sablefish.  periods  strategy  swim  reasons  p e r i o d s as can  sablefish  presented  r e p o r t e d i n s t a r v e d tuna which a l s o m o t i l e prey  Longer  the  they are doing so by r e g u l a t i n g t h e i r p e r i o d s of  contagiously distributed,  shorter  on  A r e d u c t i o n i n swimming v e l o c i t y r a t h e r than  ventilatory  1975,  i n a l l treatments  s a b l e f i s h r e g u l a t e t h e i r energy expenditure  activity.  Ware  be  but the e x i s t e n c e of optima i s w e l l accepted.  constant swimming speed of s a b l e f i s h , and  1965,  can  d i f f e r depending  r e g a r d i n g which parameters are optimized Ware  It  fed f o r a longer p e r i o d b e n e f i t more from w a i t i n g  for  searching  Even f i s h near t h e i r maintenance r a t i o n , fed only once weeks (Table 1.2), are not  inactive  Thus, although they appear to be spending 80  ( F i g . 2.2  and  2.9).  a g r e a t e r p r o p o r t i o n of  their  time  w a i t i n g f o r food,  immediate v i c i n i t y The  also  probably  search  the  should t h e i r m o t i l e prey be nearby.  standard metabolic r a t e of f i s h has been used t o compare  physiological Its  they  changes  definition,  absorptive  the  fish,  i n r e l a t i o n to  environmental  energy expenditure gives  little  of  a  information  variables.  resting,  post-  regarding  what  c o n s t i t u t e s the standard metabolic r a t e , but does provide a means of  comparing  conditions Standard and  fish  (Fry  experiencing  1947,  1957,  1971,  different  enviromnmental  Brett  Groves  1979).  in ecological  models  metabolic r a t e has a l s o been used  and  i s u s u a l l y assumed to be constant f o r any g i v e n  and s i z e of f i s h When  (Ware 1975,  temperature  Kerr 1982).  used as a p h y s i o l o g i c a l  index,  i t has been shown t h a t  the standard metabolic r a t e of f i s h changes i n response (Beamish  1964b,  Beamish  and  1972).  to  and s t a r v a t i o n  Glass 1973,  ( F i g . 2.10)  (Smith  season  1935a,  and weight (Saunders  Beamish and M o o k h e r j i i 1964,  The apparent  ration  1984)  1964a) as w e l l as temperature  Beamish 1964c, Brett  Evans  to  Brett  B r e t t and Groves 1979,  1963,  1964,  Edwards  1965, et  al.  r e l a t i o n s h i p of standard matabolic r a t e with  and days p o s t - p r a n d i a l ( F i g . 2.7)  adds f u r t h e r  the evidence t h a t t h i s b i o e n e r g e t i c parameter should only  used  in  e c o l o g i c a l models  Winberg r u l e , Winberg nature  after  careful  as d e f i n e d by Mann 1978,  (1956),  states  consideration.  and based  be The  on the work of  t h a t the r o u t i n e metabolism of f i s h  in  i s roughly twice the standard metabolic r a t e which i n t u r n  i s assumed to be constant f o r a given temperature Clearly  b,  the  and  standard metabolic r a t e Is not constant  81  fish even  size. when  temperature The the  and  r e l a t i v e magnitude of a c t i v i t y metabolism  standard  sablefish been  s i z e are i n c o r p o r a t e d .  metabolic r a t e i s low,  used  here  (Fig.  2.9  and  2.10).  r e p o r t e d f o r w i l d brown t r o u t  (Esox l u c i u s )  (Diana et a l .  1977)  at least  compared  in  the  captive  Similar results  (Young et a l .  to  1972)  have  and  on the b a s i s of s o n i c  pike  tagging  s t u d i e s , although no d i r e c t metabolic measurements were made. the  pumpkinseed  budget  based  sunfish,  on  Lepomis glbbosus,  the annual  laboratory studies consists only  13% more f o r  activity  of  metabolism  and  1984).  The  p r o p o r t i o n of t o t a l metabolism devoted  likely  to be a f u n c t i o n of the h a b i t s of the  Thus,  f o r an a c t i v e s p e c i e s such as the tuna,  where  swimming  f a r more important  (Magnuson 1966,  swam  Despite  and  this  constituted expenditures. foraging  species  examined.  Euthynnus a f i n i s ,  1969)  equilibrium  a c t i v i t y may  (Young et a l 1972,  s t e a d i l y d u r i n g the d a y l i g h t  relatively  only  (Evans  to a c t i v i t y i s  S a b l e f i s h are a c t i v e l y predatory and,  slowly  standard  i n the t o t a l metabolic budget than f o r  predators such as pike or brown t r o u t 1977).  energy  metabolism  Is r e q u i r e d to maintain h y d r o s t a t i c  and provide ram v e n t i l a t i o n  al.  87%  a  minor f r a c t i o n  Sablefish  behaviors  constant  and  appear  to  their have  mechanisms w e l l  Diana et  well  their  be  ambush  i n the  when  activity, of  In  tanks, fed.  swimming  total  metabolic  evloved  efficient  suited  to  optimizing  r e t u r n s from an i n c o n s i s t e n t food s u p p l y . After faced  with  digestive, aerobic  consuming an  a l a r g e meal,  energy  activity  budgeting  and  metabolic l i m i t s .  sablefish  problem  are  should  potentially the  combined  standard metabolic loads exceed Presumably, 82  the c o s t s  of  their  standard  metabolism change  are  fixed  over the s h o r t term.  a s s i m i l a t i n g a meal, and  f o r any g i v e n f e e d i n g  digestive  capable  of  Consequently,  and  metabolic  demands.  cannot  when d i g e s t i n g  s a b l e f i s h can o n l y r e p a r t i t i o n the I t appears  that  and  activity they  are  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 a v a i l a b l e oxygen  a c t i v i t y metabolism when necessary r o u t i n e a c t i v i t y l e v e l s were h i g h , normal  state  digestion  and  (Fig.  3.2).  If,  i n nature,  they would c o n f l i c t with  p r o c e s s i n g of food.  The  to  results  the  of  the  a c t i v i t y energy expenditure experiments  i n d i c a t e t h a t t h i s i s not  the  expenditure  case  as  r o u t i n e a c t i v i t y energy  component  of  the t o t a l energy  credibility  to  relating  expenditures observed fish.  Further,  periods  low  routine  lends  small  additional  activity  energy  i n the mass r e s p i r o m e t e r s with t h a t of w i l d r e g u l a t i o n of a c t i v i t y by  modulating  d u r i n g which d i g e s t i o n can proceed with no  swimming a c t i v i t y .  permit  the  This  a  of a c t i v i t y r a t h e r than i t s i n t e n s i t y a l l o w s p e r i o d s  quiesence from  the  budget.  is  unhindered  P e r i o d s of n o c t u r n a l  digestion,  although  sablefish also display diurnal a c t i v i t y  the of  competition  inactivity  i t i s not known i f  also wild  cycles.  When the a c t i v i t y and standard metabolic r a t e s of  sablefish  given 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 are combined i n t o a r o u t i n e metabolic r a t e and expressed  as a f u n c t i o n of r a t i o n  the r e s u l t i n g sigmoid curve assumes a two fed  every  14  days and  weekly and every four days. a similar difference  2.11)  s t a t e appearance.  Fish  s t a r v e d f i s h have n e a r l y  metabolic r a t e s which are about 25% lower  by  (Fig.  equal  routine  t h a t those of f i s h  fed  T h i s two  s t a t e system i s p a r a l l e l e d  i n the energy  sources the two groups use  83  to power t h e i r metabolic e x p e n d i t u r e s .  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 t h e i r primary energy source  ( F i g . 1.5  the  groups of f i s h  two  better-fed  and 1.6,  Table 1.1).  catabolize  e x c l u s i v e l y to meet t h e i r energy demands ( F i g . r e t a i n the l i p i d s they a q u i r e i n t h e i r d i e t s .  Conversely,  protein 1.7  almost  and 1.8)  and  Because t h e i r  diet  contains  more  demands,  the f i s h fed every four days are a l s o able to r e t a i n  portion to  than s u f f i c i e n t p r o t e i n to meet a l l t h e i r  of t h e i r d i e t a r y p r o t e i n .  I t would not be  energy  unreasonable  s p e c u l a t e t h a t s a b l e f i s h fed more f r e q u e n t l y than every  days  would  r e t a i n an even g r e a t e r p r o p o r t i o n of  a  their  four  dietary  prote i n . The  l e v e l of n i t r o g e n e x c r e t i o n i s g e n e r a l l y c o n s i d e r e d  be a d i r e c t  f u n c t i o n of the r a t e of n i t r o g e n consumption i n  (Gerking 1955, also  1971,  B i r k e t t 1969,  the p a t t e r n observed  excretion 2.1,  and r a t i o n are expressed  - 7-day  difference  interval,  49 mg/day  - 14-day  every 14 days r e t a i n e d n i t r o g e n the most  fed  every  Gerking  (1955,  macrochirus,  retain  plaice,  sole,  Table  and  182 The  concerns  efficiently,  i t least e f f i c i e n t l y ,  c l e a r l y demonstrated  fish  (Table  fish fish fed 2.1).  t h a t b l u e g i l l , Lepomis  a g r e a t e r p r o p o r t i o n of  when fed a t higher r a t e s . the  interval).  days were i n t e r m e d i a t e between these 1971)  nitrogen  On a meal to meal b a s i s ,  fed  fourth  This i s  on a d a i l y b a s i s (from  between these r e s u l t s and those c i t e d above  7 days r e t a i n e d  fish  211 mg/day - 4-day i n t e r v a l ,  the n i t r o g e n r e t e n t i o n e f f i c i e n c y .  every  1971).  i n s a b l e f i s h i f between-meal  ammonia e x c r e t i o n e q u a l s :  mg/day  S a v i t z 1969,  to  dietary  nitrogen  S i m i l a r r e s u l t s have been observed i n  and perch  ( B i r k e t t 1969), 84  and repeated  for  blueglll  by  S a v i t z (1969,  1971).  Gerking  (1955) d i d  note  a  p r e f e r e n t i a l r e t e n t i o n of l i p i d s by h i s f i s h which were a l l fed a high  lipid  diet.  T h i s agrees with the  lipid  r e t e n t i o n observed  i n w e l l fed s a b l e f i s h . The  most s i g n i f i c a n t methodological  r e s e a r c h and  t h a t c i t e d above concerns the means of  different ration levels. constant  and  the  conceivable  Gerking,  (Brody 1945,  dynamic  due  nitrogen  T h i s c o n s i s t s of amino a c i d s  i n c i r c u l a t i o n or s t o r e d  equilibrium  It i s  approaches  to the amino a c i d pool or  p. 353).  with  the  was  S a v i t z , and B i r k e t t  t h a t the u l t i m a t e reason these d i f f e r e n t  p r o t e i n s , normally in  administering  fed t h e i r f i s h on a d a i l y b a s i s .  d i f f e r e n t e f f e c t s was  resevoir  this  In these experiments the meal s i z e  interval varied.  a l l v a r i e d meal s i z e and  had  d i f f e r e n c e between  and  i n t i s s u e s , which are  protein  in  the  diet  and  f u n c t i o n i n g p r o t e i n s i n the remainder of the body.  As f u n c t i o n a l  proteins  new  become  synthesized  from  fractionated pool  resulting  even  the  Long  retention  are r e p l a c e d  amino  acid  feeding  pool  returned  i t s contents intervals  low  may  and  deplete  feeding  levels.  T h i s would  a l s o a f f e c t e d the r a t e of pool d e p l e t i o n .  proteins  subsequently  to the p o o l .  When the dietary  these  stores  whereas r e g u l a r  feeding  r e g u l a r o p p o r t u n i t i e s f o r amino a c i d  e f f i c i e n c y d i f f e r e n c e s i f the  infrequently  by  are made up out of  i n a need to r e p l e n t i s h them,  provide at  they  i n t o amino a c i d s and  becomes d e p l e t e d ,  protein.  might  disabled  explain  longer  replacement, the  feeding  protein interval  T h i s c o u l d occur when  used enzymes are c a t a b o l i z e d between feedings a f t e r  only a s i n g l e use,  whereas with  frequent  85  feeding they may  be used  more f r e q u e n t l y and e f f i c i e n t l y . The proximate efficiency  reason f o r the d i f f e r e n c e i n p r o t e i n  i n s a b l e f i s h can be found  i n t h e i r use of  metabolic f u e l when p o o r l y fed (Table 1.1). and  lipids  as  The f i s h f e d every 4  7 days meet metabolic demands with p r o t e i n c a t a b o l i s m as d i d  the f i s h s t u d i e d by the other a u t h o r s . relatively greater  constant,  amounts  efficiency. the to  retention  of  increased  As metabolic demands are  ration  allows  protein giving greater  However,  retention  protein  by s w i t c h i n g t o a l i p i d  based  conversion metabolism,  s a b l e f i s h fed every two weeks g r e a t l y improve t h e i r r e t a i n p r o t e i n and presumably t h e i r p r o t e i n  phenomena  may  be  bathypelagic fishes ration  unique  It  conserving  methods  i s , however,  protein,  infrequent  ability  reserves.  feeders  This  such  as  ( S u l l i v a n 1982) or i t may be a r e s u l t of  administration  fishes.  to  of  used  here and  common  in  the more  c l e a r t h a t s a b l e f i s h are capable  when necessary,  and basing  of  metabolism  on  lipids. 5.1 SUMMARY: Addressing,  the  hypotheses  posed i n chapter  1,  from  this  r e s e a r c h the f o l l o w i n g c o n c l u s i o n s can be drawn: 1)  The  a c t i v i t y metabolism of s a b l e f i s h  ration history. activity tanks  A sigmoid  metabolism  on  when meal frequency  i s not independent  f u n c t i o n d e s c r i b e s the dependence  ration for captive sablefish i s used t o supply d i f f e r e n t  in  of of  large  levels  of  ration. 2)  The  sigmoid  standard metabolic r a t e of c a p t i v e s a b l e f i s h f u n c t i o n of r a t i o n .  is  The f i s h appear t o operate 86  also  a  in at  least  a  two  consistently result  in  state  system  in  which  low  rations  low standard metabolic r a t e s while up to a t l e a s t a 25%  increase in  produce  higher  rations  standard  metabolic  rate. 3)  The  feeding  metabolism  (SDA)  of  sablefish  constant r e g a r d l e s s of r a t i o n h i s t o r y . the  e l e v a t i o n of metabolism  is  However, i n w e l l fed f i s h  from f e e d i n g i s more intense and  shorter  duration,  SDA  a s m a l l e r i n c r e a s e of oxygen consumption over  is  relatively  while i n p o o r l y fed s a b l e f i s h the p a t t e r n a  of of  longer  p e r i o d of time. 4)  Feeding  lipid  and  metabolism  appears  to r e s u l t p r i m a r i l y  p r o t e i n c a t a b o l i s m with a  lesser  from  both  contribution  from  protein  anabolism.  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