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The association between the black rockfish Sebastes melanops Girard and beds of the giant kelp Macrocystis.. 1976

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The Association between the Black Eockfish (Sebastes melanojas Girard) and Beds of the Giant Kelp (Bacrocystis i n t e g r i f o l i a Bory) i n Barkley Sound, B r i t i s h Columbia by Bruce Michael Leaman B.Sc., Simon Fraser University, 1972 A thesis submitted in p a r t i a l f u l f i l l m e n t of the requirements for the degree of Master of Science at the I n s t i t u t e of Animal Resource Ecology He accept th i s thesis as conforming to the reguired standard The University of B r i t i s h Columbia February,1976 (c) Bruce Michael Leaman, 1 9 7 6 » In p resent ing t h i s t he s i s in p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permiss ion for ex tens i ve copying of t h i s t he s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r ep re sen ta t i ve s . It i s understood that copying or p u b l i c a t i o n o f t h i s t he s i s f o r f i n a n c i a l gain s h a l l not be al lowed without my w r i t t e n permis s ion. Depa rtment The Un i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Date i i ABSTRACT The association between the black r o c k f i s h , Sebastes melanogs Girard and the giant kelp, Macrocy.st.is i n t e g r i f o l i a Bory, was examined in terms of habitat u t i l i z a t i o n . D i s t r i b u t i o n a l patterns of juveniles frequenting kelp beds were documented by three-dimensional positioning of observed f i s h with the kelp bed boundaries used as a frame of reference. S i g n i f i c a n t l y higher numbers of smaller (30 - 100 mm) f i s h occurred inside the kelp bed than outside, both d i u r n a l l y and nocturnally. A d i e l migration of larger (101 - 200 mm) f i s h occurred, showing s i g n i f i c a n t l y higher numbers of f i s h i n the kelp bed nocturnally. Very few of the largest (201 - 250 mm) f i s h were observed in the bed and none of these exhibited t h i s d i e l s h i f t . Wider-scale sampling indicated an increasing c l i n e i n the s i z e of f i s h when moving from inshore to the open sea. Diet analysis does not indicate dependence by the f i s h on kelp bed diet items. Transporting experiments f a i l e d to demonstrate any s i g n i f i c a n t homing a b i l i t y within the s i z e - c l a s s of f i s h studied. A r t i f i c i a l habitats employing p l a s t i c * kelp* were constructed to test the assumption that the f i s h were responding to the amount of physical shelter provided by the kelp. Results show a highly s i g n i f i c a n t numerical response by the f i s h population, to the changes i n the amount of a r t i f i c i a l shelter provided. I t i s concluded that the species u t i l i z e s the physical shelter of the kelp bed primarily as a refugium from nocturnal predators. The value of the kelp bed to the species l i e s i n i t s enhancement of recruitment through increased s u r v i v a l of the 0 to I age-classes of f i s h . i i i X l l i l 51 PAGE Abstract . . ...» i i Table of Contents i i i L i s t of Tables v L i s t of Figures . v i i Acknowledgements x 1. Introduction 1 2. Methods and materials 4 2.1 Description of the study s i t e 4 2.2 Associated f i s h at the study s i t e .................. 5 2.3 Collecting 7 2.4 Tagging and growth 7 2.5 Diet .. 9 2.6 Dis t r i b u t i o n and abundance ...............,<>........ 10 2.7 Laboratory experiments 15 2.8 Manipulative experiments ...........................16 3. Results 22 3.1 Physical and b i o l o g i c a l parameters of the s i t e 22 3.2 Distribution of the species 30 3.3 Population dynamics of Sebastes melanops ........... 35 3.4 Diet 41 3.5 Localized d i s t r i b u t i o n and abundance ..44 3.6 Environmental correlates of d i s t r i b u t i o n 54 3.7 F i d e l i t y and quantification of the association ..... 57 4. Discussion 65 4.1 General d i s t r i b u t i o n 65 4.2 Barkley Sound d i s t r i b u t i o n 69 iv 4»3 Sebastes mglano^s i n Macrocyjstis beds 73 4. 4 Diet 75 4.5 A c t i v i t i e s i n the kelp bed 79 4.6 The nature of the association ...................... 87 4.7 Significance of the kelp bed to the f i s h 90 5. Conclusions 92 6. Literature cited 94 7. Appendices ..........................107 V LIST OF TABLES PAGE T a b l e I . Abundances o f f i s h e s a t t h e s t u d y s i t e , o t h e r t h a n S e b a s t e s melanous ................................. 29 T a b l e I I . C o m p a r i s o n o f mean growth r a t e s o f S e b a s t e s m e l a n o £ s as d e t e r m i n e d by d i r e c t and i n d i r e c t measurements 40 T a b l e I I I . Major f o o d i t e m s o f e a c h s i z e c l a s s c f S e b a s t e s m e l a n o g s , w i t h a s t a t i s t i c a l c o m p a r i s o n o f t h e f r e q u e n c i e s o f dominance o f t h e s e i t e m s . . . . . . . . . . . . . . . 44 T a b l e 17. S t a t i s t i c a l c o m p a r i s o n o f t h e d i e ! p o s i t i o n s o f t h e c u m u l a t i v e t o t a l s o f f i s h o b s e r v e d . . . . . . . . . . . . . . . . 53 T a b l e V. E n v i r o n m e n t a l i n f o r m a t i o n f o r e a c h d a t e s u p p l y i n g d a t a f o r v i s i b i l i t y - d i s t r i b u t i o n a n a l y s i s . . . . . . . . . . . . . 56 T a b l e V I . I n i t i a l c o n d i t i o n s , m a n i p u l a t i o n s and r e s u l t s o f e x p e r i m e n t s e x a m i n i n g t h e p h o t o t a x i s o f S e b a s t e s melanops and t h e i n f l u e n c e o f r h e o t a x i s on t h i s r e s p o n s e 57 T a b l e V I I . Numbers, s i z e s and h a b i t a t s t o which S e b a s t e s melanop_s were t r a n s p o r t e d , t o g e t h e r w i t h t h e numbers and s i z e s o f f i s h e x h i b i t i n g homing b e h a v i o u r 61 v i Table VIII. Levels of shelter and f i s h associated with Frame I, together with an analysis of the variance i n these numbers i n r e l a t i o n to changes i n the shelter provided 63 v i i LIST OF FIGURES PAGE Figure 1. Location of the study area 6 Figure 2. Construction d e t a i l s of the fluorescein tag ..... 9 Figure 3. Sampling locations in Barkley Sound ............. 13 Figure 4. Study s i t e and the surrounding area ............. 14 Figure 5. Photograph and dimensions of the habitat frame .. 19 Figure 6. Underwater view of Frame I 20 Figure 7. P l a s t i c used in the shelter experiment 20 Figure 8. Underwater views of Frame II and the kelp bed studied 21 Figure 9. Low-level a e r i a l photograph of the study kelp bed 22 Figure 10. Bathymetric map of the study s i t e .............. 25 Figure 11. A e r i a l view of the study s i t e i l l u s t r a t i n g orientation of logs on the beach 26 Figure 12. Regression of tide range on bottom current at v i i i the kelp bed 26 Figure 13. Seasonal change i n the average occlusion of the water column by kelp tissue. 0.8 m above the substrate 28 Figure 14. Abundances and depths of Sefcastes jelanojgs capture by Oregon trawlers. 1963 - 1971 .............. 31 Figure 15. Sampling locations i n Barkley Sound for Sebastes melanop.s 3 2 Figure 16. Sebastes spp. larvae obtained i n plankton samples i n Barkley Sound. 0 - 3 m deep, January - May, 1974 34 Figure 17. Net captures of Sebastes roelanojgs at the kelp bed by s i z e classes 36 Figure 18. Population estimates of Sebastes melanoos based on recaptures and observations of tagged f i s h ......... 37 Figure 19. Age - length regressions for Sefcastes jglanops by scale and o t o l i t h aging ............................ 39 Figure 20. Freguency of diet item occurrence i n Sebastes melanops ..............................................42 ix Figure 21. Seasonal change i n the occurrence of mysids and clupeids i n the diet of Sebastes jelanogs ............. 43 Figure 22. Coincidence of kelp presence and f i s h capture at the kelp bed 46 Figure 23. Physical nature of the rock slope area ......... 47 Figure 24. Observed abundances of f i s h at the rock slope ., 48 Figure 25. Cumulative nocturnal and diurnal observations of f i s h postion at the kelp bed. 30 - 100 mm f i s h .... 50 Figure 26. Cumulative nocturnal and diurnal observations of f i s h position at the kelp bed. 101 - 150 mm f i s h .. 51 Figure 27. Cumulative nocturnal and diurnal observations of f i s h postion at the kelp bed. 151 - 200 mm f i s h ... 52 Figure 28. Changes in f i s h position with water c l a r i t y .... 55 Figure 29. Tracking record of f i s h tagged with fluorescein tag 59 Figure 30. Transporting of f i s h and returns during f i d e l i t y experiments .................................. 60 Figure 31. Fish at Frame I at 14.2 m* and 33.2 m* lev e l s X of shel ter 62 Figure 32. Surface canopy of the plants in l a te Auqust,1974 81 JCKHOJILEDGEMENTS I wish to thank the members of my supervisory committee, Drs. T.H.Carefoot, G.C.Hughes, J.D.McPhail and R.F.Scagel, for t h e i r thoughtful comments on the design of the project and a draft of the manuscript. To Dr. $.J.Wilimovsky, my research supervisor, I am gra t e f u l for c r i t i c i s m s at various stages of the research, comments regarding a preliminary draft of the manuscript and many other considerations. A f i e l d project such as t h i s necessitates considerable assistance while diving. fly colleague, Dr. Jeffrey Marliave, who gave generously of his time and expertise, aided me on numerous and often t r y i n g occasions. To the following diving partners, I am also g r a t e f u l : Glenn Cota, Myriam Haylock, Susan von M e l v i l l e , Trudie Mullin, Dan Pace, Chris Tanner and Heather Washburn. Joseph and Richard Garcia shared t h e i r many observations on the natural history of the f i s h fauna of the Bamfield region with me. Wendy Craik kindly c r i t i c i z e d i n i t i a l segments of the manuscript. Laboratory experiments were conducted and f i e l d studies were based at the Bamfield Marine Station of the Western Canadian U n i v e r s i t i e s Marine B i o l o g i c a l Society. Steve Borden of the B i o l o g i c a l Data Centre (I&RE) gave advice on s t a t i s t i c a l procedures. I thank Dr. Louis Druehl of Simon Fraser University for l o g i s t i c a l help i n the f i e l d and other considerations. Alex Thompson, lighthouse keeper at Cape Beale, and Edwin Niska, of the Oregon Fish Commission, graciously allowed me access to unpublished information referred to i n the thesis. 1 1. INTRODUCTION The biota of the coastal waters of B r i t i s h Columbia i s characterized by a d i s t i n c t seasonality of the abundance and d i v e r s i t y of species, p a r t i c u l a r l y on those segments of coastline adjacent to the open P a c i f i c Ocean. One of the most prominent f l o r i s t i c features of the summer months i s the presence of stands of large phaeophyte algae, the upper portions of which form canopies f l o a t i n g on the surface waters. There are, primarily, two algae which form these conspicuous canopies in B r i t i s h Columbia; the giant kelp, Macrpcystis i n t e g r i f o l i a Bory, and the b u l l kelp, Nereoc^stis luetkeana (Hertens) Postels and Ruprecht. Beds of these large plants provide considerable s t r u c t u r a l heterogeneity in the otherwise almost unstructured water column. This increased heterogeneity gives r i s e to a p r o l i f e r a t i o n of the species i n the animal and plant communities i n the v i c i n i t y of the beds. The biology of kelp beds has received considerable attention i n C a l i f o r n i a . North (1972) provides an extensive bibliography of research on beds of Macrocystis p y r i f e r a (Linneaus) C. figardh. The works reviewed by North are primarily of a botanical nature, though e c o l o g i c a l interactions of various animal species found i n the beds are also included. Research into the biology of kelp beds in B r i t i s h Columbia has been l i m i t e d . Scagel (1959) included B.C. studies in his review of the relationship of plants and animals i n the marine environment. There has been l i t t l e £ublished material about research on B.C. kelp beds since 1960, although a considerable amount of e f f o r t has been expended in these habitats, including both f l o r i s t i c and f a u n i s t i c studies. Many animals (invertebrate and vertebrate) found i n kelp beds have a direct relationship with kelp plants. They l i v e either i n or on the plants, or the plants provide t h e i r trophic resource base. Species with i n d i r e c t relationships are those which may be associated either with kelp plants themselves, or with the associated f l o r a and fauna. The f i s h fauna of kelp beds may contain either type of species. The fishes of kelp beds have been examined both as a community (Limbaugh, 1955; Davies,1958; Quast,1968; Ebeling et al.,1972) and as i n d i v i d u a l kelp bed species (Skogsberg,1939; Wales,1952; 0'Connell,1953; Boedel,1953; Williams and Williams,1955; P h i l l i p s , 1957; Follett,1960; Limbaugh,1961,1962; Turner and Ebert,1962; Gotshall et al.,1965). A l l of the above papers dealt with f i s h e s in C a l i f o r n i a kelp beds and, in general (e'xcept Limbaugh, 1961), d e t a i l their interactions with the plants in a qu a l i t a t i v e fashion only. The fishes of B.C. kelp beds have not received a great deal of attention; I know of no published material that deals s p e c i f i c a l l y with these forms. Sebastes melangps Girard i s the most common n e r i t i c f i s h resident i n the kelp beds of Barkley Sound,B.C. Juveniles of t h i s species are found abundantly i n beds of Macrocystis iii§3£if2lis a n d i n lesser amounts i n beds of Nareocystis 1 ueJUsejuia.» Previously, I had observed that the abundance of f i s h was, roughly, inversely correlated with t h e i r s i z e , and that some f i s h could be found consistently within the kelp bed. Larger f i s h , however, were not found i n or near kelp beds, but instead, near the open coastline. 3 The present study was designed to examine the hypothesis that S. jelanojas i s dependent upon kelp beds i n some fashion and that t h i s f i s h undergoes a t r a n s i t i o n i n habitat association with age; from an inhabitant of kelp beds when young, to an inhabitant cf moderate r e l i e f coastal areas when older. In the i n i t i a l stages of the study I attempted to determine how the f i s h uses the kelp bed as a habitat. Several aspects of the ecology of the species were examined to categorize the l i n k s between the f i s h and the kelp bed. The l a t e r stages of the project were la r g e l y occupied with the testing of a subsequent hypothesis as to the primary nature of the association betseeen the two species. 4 2. METHODS AND MATERIALS The study was conducted during the period June,1973 - September,1974 in Barkley Sound, near Bamfield,B.C. The f i e l d s i t e was located i n a small group of i s l e t s (Boss Islets) at position 48°52.45*N, 125°09.65»8; the kelp bed studied was situated in a small cove having a southwestern aspect (Figure 1). 2.1 Description of the study, s i t e The cove containing the kelp bed studied was characterized i n terms of several physical and b i o l o g i c a l parameters: area, topography, current v e l o c i t i e s and kelp density. (i) The area of the study s i t e was calculated from a large scale map of the v i c i n i t y , as well as a e r i a l and surface photographs taken at the same t i d a l heights, The t o t a l area of the s i t e was taken as the average of these three measurements. ( i i ) Topography of the bottom was determined by sounding with a metred, hand l i n e . The values obtained were then incorporated into a bathymetric map. ( i i i ) Current magnitudes were extrapolated from d a i l y wind and sea state data taken at Cape Beale lighthouse, approximately 12.8 km from the study s i t e . In s i t u current measurements were taken at the study s i t e over a short period of time. These data were then related to the Cape Beale data and a c o r r e l a t i o n plot constructed for the purposes of extrapolation throughout the year. The in s i t u measurements were obtained with a TSK Flow 5 Meter 1 over a f i f t y - d a y i n t e r v a l during May - June 1974. (iv) Kelp density was estimated with a visual occlusion method employing SCUBA. A checkered, plywood panel 0.83 m2 (9 f t 2 ) was viewed from 2 m distance, normal tc the panel, while the panel was held v e r t i c a l l y , i t s base i n contact with the substrate. Kelp density was taken as the mean percentage of the panel occluded by the kelp, when viewed from the four cardinal compass points. This procedure was repeated approximately once per week, at both random and s p e c i f i c locations i n the kelp bed, during the periods of kelp presence. 2.2 Associated f i s h at the s i t e The f i s h assemblage of the area was p a r t i a l l y known from previous work (Druehl, Green and Leaman, unpublished data) i n t h i s area and other s i m i l a r s i t e s . This work had included both netting and ichthyocide sampling. A l l species (other than §• ffl§isa2ES) were enumerated during the netting program of the current study to determine the t o t a l f i s h complement of the s i t e . 1 Tsurumi-Seiki Kosakusho Co., Yokohama 6 Location of the study area 7 2.3 Co l l e c t i n g Fish [unless sp e c i f i e d otherwise, • f i s h ' r e f e r s to Sebastes melanoDS ] were co l l e c t e d for d i e t , population and movement studies with nylon monofilament g i l l nets of 1.27 (0.5 i n ) , 2.54 (1.0 i n ) , 3.81 (1.5 i n ) , 5.08 (2.0 in) and 6.35 (2.5 in) cm (wet, stretched mesh) sizes. A l l nets were not employed simultaneously, rather, two nets, of 2.5** cm difference i n mesh s i z e , were set at any given time. Nets were set 1.0 - 1.5 hours before sunset and retrieved <0.5 hours after dawn i n order to: (i) maximize the number of l i v i n g f i s h i n the net, and (i i ) improve the probability of i d e n t i f y i n g the stomach contents of the f i s h . Nets were set i n a T-shaped or L-shaped pattern at various locations, i n and out of the kelp bed. Specimens of S. melano£s were also obtained from ether locations to complete an age-length regression. These additional f i s h were obtained using a s l i n g spear and a Norwegian-type cod j i g . 2.4 Tagging and growth Fish recovered from the nets a l i v e were anaesthetized, measured (TL), tagged, allowed to recover from the anaesthetic and released. The anaesthetic employed was MS-222 (tricaine methane sulfonate). Several d i f f e r e n t models of tags were employed for the population study, a l l of the nylon 1 anchor' type (Dell,1968). A l l tags were inserted in the dorsal musculature of the f i s h , ventral to the base of the dorsal f i n . An additional tag (Figure 2) was developed for short term 8 tracking studies. This tag was composed of a variable length of f i v e mm (I.D,) glass tubing which was mated to the basic nylon anchor tag. The tube was then f i l l e d with powdered Na~ fluorescein dye and the open end of the tube plugged with epoxy glue or s i l i c o n e sealant. Fish were tagged and the epoxy or s i l i c o n e plug removed immediately prior to release. I t was possible to track the f i s h from the surface ( i f water c l a r i t y permitted), or from i n the water, by the t r a i l of dye which diffused from the tag as the f i s h swam. The length of time over which the tag was e f f e c t i v e was a simple function of the amount of dye i n the tag (and, hence, of tag s i z e ) , e.g., a 55 mm tag lasted approximately f i v e hours. Data for population estimates were gathered both frcm net sampling and from observational sweeps through the study area, using SCUBA. Population estimates were generated through multiple censusing of the f i s h i n the area for r e l a t i v e numbers of marked and unmarked f i s h , using the modified formula for a Schnabel capture-recapture estimate of Chapman (1954). Growth of the f i s h was measured by growth of recaptured f i s h , and interpolation from an age-length regression. The regression was constructed from data taken from a l l s i z e classes of f i s h . Fish were aged by both scale and o t o l i t h annuli counts. 9 Figure 2 Construction d e t a i l s of the fluorescein taq 2.5 Diet Fish recovered dead in the g i l l nets were frozen, upon return from the f i e l d and analyzed at a l a t e r time. Only the contents of the stomachs were analyzed because i n t e s t i n a l contents were, generally, unrecognizable or impossible to t o t a l l y recover. Stomachs were removed from the animal, fullness estimated, and the contents emptied into a finger bowl for microscopic examination. The s a g i t t a l o t o l i t h s and a scale sample were alsc remcved from a l l size classes of the f i s h recovered. 10 The analyses of the stomach contents were summarized on forms, an example of which i s shown i n Appendix I. Contents were scored by percentage occurrence and by percentage dominance, A dominant item was any item which represented > 50% of the t o t a l volume of the contents, estimated by eye. The dominant item selected on t h i s basis yielded a general estimation of the major components of the f i s h ' s d i e t . Volume was the basic c r i t e r i o n employed because an analysis based on the freguency of occurrence of items alone confers equal s t a t i s t i c a l weight to a l l occurrences of any given item, without regard to the guantity of the item i n the stomachs, A volume- based analysis has the additional advantage of incorporating some aspects of the energy contribution of diet items, although r e s u l t s regarding energy input through diet items must be interpreted cautiously i f no data are available regarding c a l o r i c content and assimilation e f f i c i e n c y (Paine,1971), Specimens whose stomach contents exhibited no c l e a r l y dominant item, or whose contents were too digested to determine dominance, were assigned no dominance. 2.6 Dis t r i b u t i o n and abundance The primary emphasis of the study was centred on the single kelp bed, but the o v e r a l l regional d i s t r i b u t i o n of Sebastes melanogs »as also investigated through j i g and speargun captures, returns from a t r o l l i n g cruise, reports from l o c a l fishermen and extrapolations from published data on the geographic and bathymetric d i s t r i b u t i o n of the species. J i g and speargun samples were made on the southeast side of Trevor 11 Channel from Aguilar Point to Whittlestone Point; the t r o l l i n g cruise covered the area at the mouth of Trevor Channel and that between Folger Island and Edward King Island (Figure 3). The technique employed in establishing the d i s t r i b u t i o n and abundance of S. melanoj3£ at the study s i t e was to enumerate and size f i s h during underwater observational sweeps. The observational data encompassed physical parameters at the time of observation and information on the f i s h sighted. A t y p i c a l observational summary sheet i s i l l u s t r a t e d i n Appendix I I . Sizes of f i s h were estimated and when necessary or possible, size was measured against background features, to which the f i s h could be adequately compared, using a pencil marked in centimetres. The accuracy of size estimation was checked by comparing the estimate with data cn f i s h which were tagged or marked and observed on the same day. The position of the f i s h i n r e l a t i o n to the edge of the kelp bed was determined by comparison of sighting location with position along metred t r a n s i t l i n e s established on the bottom. There were three such l i n e s of 35 mm metred, polypropylene rope, l a i d out 15 m normal to the edge of the kelp bed (Figure 4). The l i n e s were anchored to bolts set into pre-packaged units of concrete which had been formed into rock crevices. These l i n e s were only necessary during the i n i t i a l observational dives u n t i l f a m i l i a r i t y with the microtopography of the area was achieved, allowing accurate estimate of position. The observational sweeps were varied as to st a r t i n g point, to minimize behavioural responses which could give r i s e to patterned positioning of the f i s h . 12 Observation dives d i e l a c t i v i t i e s of the t h e i r d i s t r i b u t i o n and attempted to monitor f i s h , i n addition to abundance. a l l aspects of the seasonal features of Figure 3 Sampling lo c a t i o n s i n Barkley Sound Imper ia l Eagle Channel Sanford Island Transit line Frame II Kelp boundary F r a m e l — ( - • Boundary rock substrate Trevor Channel Figure 4 Study s i t e and surrounding area 15 2.7 L a b o r a t o r y £2LBi:£i.EiL2£§ S e v e r a l l a b o r a t o r y e x p e r i m e n t s were c o n d u c t e d a t t he WCUMBS1 B a m f i e l d Ma r i ne S t a t i o n , i n an a t t e m p t t o r e s o l v e c o n f l i c t i n g f i e l d o b s e r v a t i o n s on n o c t u r n a l b e h a v i o u r of t he f i s h . The f i s h e x h i b i t e d d i f f e r e n t d i s t r i b u t i o n a l p a t t e r n s unde r , a p p a r e n t l y , s i m i l a r n o c t u r n a l c o n d i t i o n s . O b s e r v a t i o n s s u g ge s t ed t h a t l i g h t and c u r r e n t might be i n t e r a c t i n g t o d e t e r m i n e some a s p e c t s o f t he n o c t u r n a l d i s t r i b u t i o n a l p a t t e r n . A s e r i e s of e x p e r i m e n t s was conduc ted i n wh i ch s t udy f i s h were s u b j e c t e d t o v a r y i n g i n t e n s i t i e s o f c u r r e n t and l i g h t , t o d e t e r m i n e i f t h e r e was any i n t e r a c t i o n betweeen t h e i r p h o t o t a c t i c and r h e o t a c t i c r e s p o n s e s . E x p e r i m e n t s were conduc ted i n a 2700 l i t r e aguar ium i n s i d e a shaded a r ea ( i l l u s t r a t e d i n Append ix I I I ) , w i t h f i s h b e i n g h e l d i n a s i m i l a r aguar ium p r i o r t o e x p e r i m e n t s , A s i n g l e 40 wat t m i c r o s c o p e bu lb c o n t r o l l e d by a r h e o s t a t s u p p l i e d t h e l i g h t . A c t u a l l i g h t i n t e n s i t i e s were d e t e r m i n e d t h r o u g h i n t e r p o l a t i o n f rom a p l o t o f r h e o s t a t v a l u e s v e r s u s l u x p r o d u c e d , as measured w i t h a photometer ( P h o t o v o l t C o r p o r a t i o n , Model 501-M). E x p e r i m e n t a l c u r r e n t r eg imes were produced w i t h t h r e e s u b m e r s i b l e pumps (773 1/hr each) wh ich were p o s i t i o n e d a t s e v e r a l l o c a t i o n s w i t h i n t he agua r i um. The p o s i t i o n o f t h e f i s h and t h e o r i e n t a t i o n i n t h e water co lumn, assumed under each e x p e r i m e n t a l c o n d i t i o n , were n o t e d . B e h a v i o u r between changes i n l e v e l s of t he f a c t o r s was r e c o r d e d . U n i v e r s i t i e s Mar ine B i o l o g i c a l S o c i e t y 1 Western Canad ian 16 2.8 Mani. £ ulat i ve experiments Two f i e l d experiments were conducted to determine the f i d e l i t y of the association between the f i s h and i t s habitat, and the nature of the re l a t i o n s h i p between the amount of physical shelter provided and the number of f i s h using i t . After these experiments, an a r t i f i c i a l habitat, simulating the shelter aspect of the kelp bed, was constructed to examine the nature of the relationship between the f i s h and the shelter provided by the kelp. (i) Previous work i n Barkley Sound (Druehl, Green and Leaman, unpublished data) had shown that S. melanojgs (and ether fish) were attracted to a r t i f i c i a l 'beds' of kelp established in areas at least 70 m from the nearest kelp bed. These 'beds' consisted of elevated, rectangular frames covered with wire mesh. Plants, attached to bricks, were placed on the mesh in various densities. I repeated the essential features of t h i s experiment without the metal frame, employing thirteen plants attached to clay b r i c k s . These plants were taken from a kelp bed approximately 1000 m distant from the study s i t e and were established at a location approximately 30 m from the nearest kelp. The edge of the existing bed at the study s i t e was also extended 8 m, employing more plants from the same location as those used i n the previous experiment. This second experiment was designed i n an attempt to extend the contiguous d i s t r i b u t i o n of the f i s h observed at the edge of the study kelp bed during d a i l y observations. A t h i r d experiment attempted to determine i f there was any f i d e l i t y i n the re l a t i o n s h i p of the f i s h and a given habitat 17 location or a given habitat type. Fish were captured and tagged at the study s i t e and then transferred to several areas at varying distances from the s i t e . In the instances where the f i s h were transported to another habitat containing Sebastes melanop_s, an equal number of s i m i l a r sized f i s h were removed from t h i s habitat, to ensure that the transported f i s h were not excluded frcm occupying t h i s habitat by density-dependent factors. While the removal of these f i s h may have avoided a s t r i c t l y numerical exclusion of the transported f i s h , i t did not necessarily preclude, nor was i t possible to control f o r , behavioural exclusion. The assumption must be made, therefore, that no antagonistic reactions existed between the two groups of conspecifics. The transported f i s h were tracked by net capture on the l i n e of their transport to determine i f they could return (•home*) to the location from which they were taken; or whether they would remain i n the new location to which they were transported. In addition, observations were made at the •home' and the 'transport 1 s i t e s to determine the fate of the transported f i s h e s . ( i i ) The capture of f i s h by size class over time was monitored and compared with changes i n kelp density. The shelter provided by the kelp was estimated as kelp density, obtained by the method described i n part 1. (iv) (p.7) of thi s section. The a r t i f i c i a l habitat (Figure 5) was constructed of 1.9 cm diameter iron r e i n f o r c i n g rod with corner brackets and rod holders brazed onto the frame. The dimensions of the habitat frame are given i n the fig u r e . The frame was p a r t i a l l y 18 asssembled, transported to the study s i t e and assembled under water (Figure 6). Shelter at the frame was provided by pieces of green 0.15 mm p l a s t i c cut into a shape to simulate kelp plants (Figure 7). The s t r i p s were cut into several lengths to enable them to reach the substrate from the supporting rods; the p l a s t i c was weighted at the bottom and attached to the supporting rods with clothes pins. The shelter provided by the p l a s t i c was taken to be the combined area of the s t r i p s . The amount of shelter provided by the p l a s t i c was changed p e r i o d i c a l l y , by adding or removing pieces of p l a s t i c , and the numbers of f i s h associated with the frame was recorded during observation dives. A second habitat frame was constructed and modified such that the pieces of p l a s t i c floated upward from the substrate (Figure 8), rather than hanging down as at Frame 1. Observations and manipulations at t h i s frame were s i m i l a r to those conducted at Frame 1.  20 Figure 7 P l a s t i c u s e d i n t h e s h e l t e r e x p e r i m e n t s 21 F i g u r e 8 U n d e r w a t e r v i e w s c f Frame I I and t h e s t u d y k e l p bed 22 3. RESULTS 3.1 Physical and b i o l o g i c a l c h a r a c t e r i s t i c s of the s i t e The study cove comprised an area of appproximately 1000 in2 (995 m2) , as calculated by measurements taken from an a e r i a l photograph, obtained through the Department of Lands, Forests and Water Resources of the Province of B r i t i s h Columbia (BC 726 1-052). The kelp bed did not occupy the entire area of the cove, rather, the surface canopy of the kelp was estimated from a low - level a e r i a l photograph (Figure 9) to be approximately 700 a 2 , or 10% of the area of the cove. Figure 9 Low-level a e r i a l photograph of the study kelp bed 23 Figure 10 i s a bathymetric map of the s i t e constructed employing the data obtained through hand soundings, The substrate i s not uniform throughout the cove; there are several anomalies which affect the d i s t r i b u t i o n a l patterns of the f i s h . The most prominent of these are the two trenches at the east and west sides of the cove, These depressions below the general l e v e l of the substrate have important ramifications on both the diurnal and nocturnal a c t i v i t i e s of the juvenile Sebastes me l a nop_s. a second anomaly at the s i t e i s the f l a t central portion of the cove, delineated by the crosshatched area i n Figure 4 (p. 14). The s i g n i f i c a n c e of t h i s central area i s i t s substrate; the substrate of t h i s area i s sand with scattered, small (<5 cm diameter) rock, rather than the continuous, conglomerate rock of the rest of the cove. Since they reguire rock substrate for attachment, the plants are i n very low abundance i n t h i s area. an examination of the low - l e v e l photograph i l l u s t r a t e s t h i s discontinuity. The hydrographic conditions at the s i t e were almost exclusively the r e s u l t of conditions i n Imperial Eagle Channel. Infrequent, large scale (>70 km/hr) winds from the southeast gave r i s e to waves s t r i k i n g the s i t e from t h i s d i r e c t i o n . Predominant winds i n the summer months were from the west, southwest and northwest and while southeast and east winds did occur during the summer, they were generally of too weak to generate waves impinging on the s i t e from t h i s d i r e c t i o n . The resu l t of the orientation of the s i t e and the seasonal meteorological conditions i s that the primary wave force was received onto the mouth of the cove from Imperial Eagle Channel. 24 The position and the orientation of the logs i n the s u p r a l i t t o r a l region (Figure 11) of the cove i l l u s t r a t e s the uniformity of t h i s exposure. The second major hydrographic influence in the region of the s i t e was that of t i d a l l y generated currents passing through the two small channels, separating Sanford Island and Fleming Island, which l i n k Trevor Channel with Imperial Eagle Channel. While t i d a l currents did not generate bottom currents i n the immediate v i c i n i t y the kelp bed studied (Figure 12), their e f f e c t was considerable at the rock slope just to the east of the kelp bed. On extreme tides (4.5 m) t i d a l currents as rapid as 2.5 m/min were recorded at t h i s l o c a t i o n . The influence of these t i d a l l y generated currents on f i s h d i s t r i b u t i o n w i l l be presented i n part 3.6 of th i s section. The seasonality of the oceanographic conditions at the s i t e was par a l l e l e d by a concomitant seasonality cf kelp presence. Figure 13 d e t a i l s the change, over time, of the occlusion of the water column by kelp tissue. The degeneration of kelp ti s s u e , beginning i n August, i s a resu l t of several b i o l o g i c a l and oceanographic processes (e.g., degree of epiphytization, sea temperature, grazing pressure, e t c . ) . While a l l of these factors influence the amount of tissue in the water column, the dramatic decrease i n occlusion i n August/September was cl o s e l y correlated with the magnitude of south, southwest, and west winds or, nfore generally, the amount of stress to which the plants were subjected. 25 Figure 10 Bathymetric nap of the study s i t e Regression of tide range on bottom current at the kelp bed 27 The f i s h assemblage at the study s i t e , other than Sebastes melanojas, i s presented in Table I. The sampling methods employed d i f f e r in t h e i r effectiveness to sample any given segment of a habitat, rotenone i s most e f f e c t i v e when sampling those fishes associated with bottom features and g i l l nets are most e f f e c t i v e in obtaining larger water column f i s h . The overlap between the two methods i s , generally, a r e s u l t of either large specimens of epi-benthic f i s h being caught in g i l l nets, or juveniles of water column forms being affected by the rotenone. 28 OQULEION OF WATER DULJfvM BY KELP 1373-74 1DO. 80.1 BOol 70-1 60-1 50-1 40.1 30.1 S0«1 ajo«l -\ h -\ 1 1 \- H 1 h ^ JU AU SE CC ND DE JA FE MA AP MY JM J U A U SE 1373 1974 TIME Figure 1.3 Seasonal change i n average water column occlusion by kelp t i s s u e . 0.8 m above the substrate 29 TABLE I Abundances of f i s h e s , o t h e r than Sebastes melanojgs, a t t h e st u d y s i t e as determined t h r o u g h g i l l n e t and c h e m i c a l s a m p l i n g . G i l l n e t s a m p l i n g , t h i s s t u d y ; rotenone sampling,1971 S p e c i e s E n g r a u l i s mordax Hexagrammos decagrammus Sebastes cau.ri.nus E h a c o c h i l u s vacca S g u a l u s aca.nth.ias Cymatogaster a g g r e g a t a H e m i l e p i d o t u s h e m i l e p i d o t u s Embiotoca l a t e r a l i s A u l o r h y n c h u s f l a v i d u s Hexagrammos s u p e r c i l i o s u s fieriuccius p r o d u c t u s B l e p s i a s c i r r h o s u s R a j a b i n o c u l a t a Clupea harengus Oncorhynchus k i s u t c h Salmo g a i r d n e r i P o r i c h t h y s n o t a t u s S e b a s t e s p a u c i s p i n i s Ophiodon e l o n g a t u s S c o r p a e n i c h t h y s marmcratus A r t e d i u s meanyi O l i g o c o t t u s maculosus X i p h i s t e r a t r o p u r p u r e u s A r t e d i u s l a t e r a l i s P h o l i s l a e t a X e r e r p e s fucorum A n o p l a r c h u s purpurescens O l i g o c o t t u s s n y d e r i A p o d i c h t h y s f l a v i d u s l i p a r i s f l o r a e A r t e d i u s h a r r i n g t o n i G i b b o n s i a m o n t e r e y e n s i s A r t e d i u s f e n e s t r a l i s Enophrys b i s o n 30 3,2 D i s t r i b u t i o n of the species The scope of the study was not s u f f i c i e n t l y large to investigate the widespread d i s t r i b u t i o n of the various l i f e stages or size classes of S. melanojDS; however such information for adults has been obtained from an unpublished report on commercial trawl f i s h i n g along the P a c i f i c coast (kindly supplied by Mr. Edwin Niska of the Oregon Fish Commission). Figure 14 i s a map of the central P a c i f i c coast of North America on which are indicated the positions, depths and yields of the adults of the species that were collected by Oregon - based trawlers. The bathymetric mode of abundance, as determined through t h i s type of sampling, i s i n the 0 - 53 m depth range. The coastal regions, at the positions where these catches were made, are such that the depth range sampled i s less than 10 km from the coa s t l i n e . A l i m i t e d amount of sampling, other than at the study s i t e , was done in Barkley Sound during the project. Figure 15 i s a map of Barkley Sound on which are marked the numbers and average sizes of f i s h caught at several locations during t h i s sampling program. An increasing c l i n e in the average size of the f i s h i s indicated when sampling from north to south i n Trevor Channel. While the abundances of smaller size class juveniles (<150 mm) in Barkley Sound were not extensively investigated, observational samples i n Wacrpcystis beds and in beds of the more exposed plant, Nereocystis luetkeana, show s i g n i f i c a n t l y higher numbers of S. malanops i n beds of the less cumatophytic plant. 31 Figure JU Abundances and depths of Sebastes melanops capture by Oregon t r a w l e r s . 1963 - 1971 Figure J5 Sampling in Barkley Sound for Sebastes melano£S 33 Plankton toss in Earkley Sound yielded numerous Sebastes spp. larvae (Figure 16), however, the appearance of 40 - 50 mm juveniles of S. melanojas i n mid-May indicates that none of the specimens c o l l e c t e d was of t h i s species. These 40 - 50 mm juveniles began to appear in the area of the kelp beds soon after the i n i t i a t i o n of Microcystis sporophyte growth. S i g n i f i c a n t l y higher numbers of Sebastes spp. larvae were obtained in sheltered waters, both i n surface and i n subsurface hauls, than in open channels (e. g., 700 vs. 3, Trevor Channel vs. Ross I s l e t s ) . The absence of any published description of the larva of S. melanges, as well as the large degree of i n t r a s p e c i f i c variation and i n t e r s p e c i f i c s i m i l a r i t y i n larvae of the genus (S.J.Westrheim, personal communication) make the assignment of s p e c i f i c i d e n t i t y to any of the larvae questionable, at best. No f i s h obtained at the study s i t e were sexually mature and no gravid females were obtained in the course of sampling i n the rest of Barkley Sound. A l l females caught which were sexually mature had ovaries at the stages 2 or 7 of Westrheim et a l . (196 8).  35 3.3 Population dynamics of Sebastes jelanop_ s at the s i t e C o l lections of S. jelanojp_s, obtained by nettings over the period of the study are presented by s i z e classes i n Figure 17. The information presented in these figures was collected during the course of the population sampling program, conducted to obtain data cn the dynamics of the species i n the area. Population estimates of the numbers of f i s h residing i n the area of the study s i t e were derived separately from net captures of tagged f i s h and from underwater observation of r e l a t i v e numbers of marked and unmarked f i s h {Figure 18}. 'Besidence* of f i s h at the s i t e was assumed on the basis of both direct and i n d i r e c t evidence; the former, being recaptures of f i s h several times over the course of the study, including overwintering i n d i v i d u a l s , and the close s i m i l a r i t y i n population estimates from season to season. Indirect evidence of residence includes observations of tagged f i s h i n the area of the s i t e over long periods of time, with no sightings in adjacent areas, and i n s i t u tracking of f i s h movements with fluorescein tags. f€T CAPTURES 1373-1974 30-100 M-M- 50-. 40- as... 30... £5... so.. is... SO: s... f£T CAPTURES 1S73-1S74 101-350 M-M- 1 . . . 1 ~ - 1 _ 1 - 1 _ 1 1 1 1 1 1 1 1 1 O I A U S E O C N O C E J A F E M A A P M V J J 1373 1S74 Tike .i l*T CAPTURES 1S73-1S74 151-300 M-M- JU AU 30. SO- 15.1 so.. 40. b = ^ 33'.. IS... I' I . I I 1 1 1 i H J J AU SE 0C NO 0E JA FE UA AP W J M J U A U 1373 1374 TttE fCT CAPTURES 1S73-1S74 E01-E50 M-M- u. ED' I S - l 10.1 5-1 1 1 1 1 1 1 1 1 1 1 1 1 J U A U S E O C N D C E J A F E M A A P M V J H 1373 1S74 TttE TIME Figure 17 Net captures of Sebastes melanops at the kelp bed by size classes 37 CHAPMAN POP- ESTIMATE - OBSERVATIONS 13000. 18000' HOOO. 1C000< sooo< BOOO- 7000. eooo? sooo> •4000- 300O> aooo* iflOO. 0- f < 1 1 1 1 1 1 1 1 1 1 1-J U A U 5 E 0 C N C I D E J A F E M A A P M Y J l JU AU 1373 JS74 CHAPMAN POP- ESTIMATES - NETTUSCS EE CC | •4500- 4300*. 3900«. J 3B00-. : 3300-. 3000•. : : 8700'. : : SCO.. E1O0.. : laoo.. • ! : 1500.. 13X1.. 3X>- : : BOO: 300-. < i i 0* i -XX- H 1 1 1 1 1 1 1 1 1 (- H 1 J J A U S E O C r C I D E J A F E M A A P M i r j ^ J U A U 1S73 1374 T I M E Figure J 8 Population estimates of Sebastes melanpjas based on recaptures and observations of tagged f i s h 38 In addition to the population estimates generated with recapture data, changes in the lengths of these f i s h during the i n t e r v a l from i n i t i a l tagging allowed c a l c u l a t i o n of their growth rates. Table II provides mean growth rates for two s i z e classes of f i s h , as determined by the above method. Included i n t h i s table are the growth rates for these s i z e classes as determined by regressions of age upon length, with age determination by both scale and o t o l i t h annuli estimation (Figure 19). A Chi-sguared test for differences i n the growth rates of the two size classes (as determined through recapture data) showed a s i g n i f i c a n t decrease (p<.05) in growth rate for the 151 - 200 mm f i s h ; the n u l l hypothesis i s that the rate was constant through the entire size range examined. There was also a s i g n i f i c a n t difference between the growth rates of f i s h whose growth was interpolated from regression plots and those of 101 - 150 mm f i s h . The r e s u l t s presented in the table i l l u s t r a t e both the advantages of d i r e c t growth c a l c u l a t i o n and the lack of resolution of growth afforded with interpolation of age-length regressions. The age classes, corresponding to these s i z e ranges, are also presented in t h i s table. 39 AGE-LENGTH REGRESSION SCALES S -8 E5> SO- 75iCO425<130^a»SSOe75a30SS5SOa75-«X)-e5-)SO-«75e0O. LENGTH IN VM« AGE-LENGTH REEFEESIDN OTDLXTHS !. Y = -0-4336 * C-3JE7-£:-01«X N = -44 5 0> £5« 50- 7 5 < U X ) < 1 2 5 d 3 3 < L 7 5 e 3 0 e S ' ^ e 7 5 a 0 0 3 S a 5 0 a 7 5 ^ 0 - 4 S - ^ ^ 5 S O O - LENGTH IN MM. Figure 19 Age-length regressions f o r Sebastes melanops by s c a l e and o t o l i t h aging 40 TABLE II Comparison of mean growth rates of Sebastes mel,ano£S as determined by d i r e c t (recapture) and i n d i r e c t (aging) measurements r - — • - T ~ T _ T T | Size-class j Age | Recaptures | Growth rate 1 „ i . ., i _. , i i — ' - j - — —1 - i • 1 • i | 1. 101-150 mm I I-II | 9 | 104 mm/yr | j 2.151-200 mm III-III ] 10 | 58 mm/yr j i i i i ' j J Aging Method I No. | Size Range J Growth rate | ] j . , ̂,,.,, , _ i ] ! 1 + t ! |3.Otolith aging|44 f i s h | 84-484 mm | 60 mm/yr | j4.Scale aging |25 f i s h ! 98-515 mm | 68 mm/yr J , | . i . ^ j j Growth rate difference| Chi-sguared value j | 1. vs. 2. | 12.76* | I 1. vs. 3. 1 11.94* | I 1. vs. **. 1 7.73* ! | 3. vs. 4- 1 0.49 j i J. ,. , . J * - s i g n i f i c a n t l y d i f f e r e n t (p<0.05) 41 3.4 Diet Analysis of the stomach contents of net-caught specimens was performed i n two ways: - freguency of occurrence of diet items i n the stomachs; and - freguency of dominance (as previously defined) of any item in a given stomach. These data are d i f f e r e n t i a t e d for a l l f i s h combined, and for the three s i z e classes analyzed (Figure 20). The r e s u l t s of Chi- sguared s t a t i s t i c a l t e sts for d i f f e r e n t i a l frequencies of dominance, between the two most common diet items for each s i z e class are l i s t e d i n Table I I I . The major habitat where each of these d i e t items i s found i s also included in t h i s table. A l l of the si z e classes examined exhibited a r e l a t i v e l y narrow t o t a l diet spectrum. The primary food input was r e s t r i c t e d to two d i f f e r e n t diet items and was consistent for any s p e c i f i c time cn an annual basis. The seasonal change in the occurrence of the two primary diet items was examined as the number of f i s h of each s i z e class whose stomach contained the item. Figure 21 represents the c o l l a t i o n of t h i s information for the period of the study. *2 DIET ITEM5 - ALL FISH Amphipods J.Empty Polychaetes MZMMMMZM ; ))>n Mysids Clupeids Unident. Fish Cumaceans Eggs •Icopepods lEuphausids Zoea H 1 1 1-0. 10. • 3D. 30- -40. 3D. GO- 70- PERCENT FREOLENCY DIET ITEMS* 30-100 M-M- Empty Amphipods Crust. Remains Clupeids mm Unident. Fish Euphausids _) 1 1 ! 1 |_ 0. ID. 33. 30. O- 50- 60- 70- B0> 9Q.1XX). PERCENT FREOLENCY DIET ITEM5 101-150 M-M- DIET ITEMS 151-200 M-M- W2M2MMMZMM' Empty Mysids Amphipods M C r o b s ' jH Crust. Remains . J Mussels W//////////////////M Clupeids Unident. Fish Copepods Zoea 0- ID- SO- 3D- AO- SO- BO- 70- PERCENT FREOJENCY Empty Polychaetes Mysids Amphipods Crabs J Mussels Uniaent. Fish Zoea Clupeids _ 1 1 1 1 • 1— 1 1 1 » 0> 10- SO- 30- 40. 50- BO- 70- BO- 90- PERCENT FREOJENCY frequency ot d i e t it«» occarr«nc« i n Ssbj^jcjj lsl3Q2£3. Open bars « o c c u r r e n c e , kittened bars • do»ln»nc« 4 3 SEASONALITY CF DIET 1XOJRRENCE TIME Figure 2JT_ Seasonal change i n the occurrence of mysids and clupeids i n the d i e t of Sebastes melanops. 44 lASkl III Major f o o d i t e m s o f each s i z e c l a s s of S e b a s t e s melanoDs, as deter m i n e d t h r o u g h gut a n a l y s i s , w i t h a s t a t i s t i c a l comparison of t h e perc e n t a g e f r e g u e n c i e s of dominance o f t h e s e i t e m s S i z e C l a s s Stomachs Examined Major Food Items Type F r e g . of Dominance 30-100 mm 10 c l u p e i d s u n i d . f i s h e u p h a u sids P P 66.7%* 33. 7% 101-150 mm 79 mysids c l u p e i d s P P 51.7S* 36. 2% 151-200 mm 39 c l u p e i d s mysids amphipods P P B 73.7%* 10. 5X * - s i g n i f i c a n t l y g r e a t e r (p<.05) P - p e l a g i c / w a t e r column form B - b e n t h i c f o r m 3.5 L o c a l i z e d d i s t r i b u t i o n and abundance ( i ) S e a s o n a l : F i s h were not p r e s e n t t h r o u g h o u t the ye a r a t th e l o c a t i o n o f t h e s t u d y k e l p bed, r a t h e r , f i s h were p r e s e n t o n l y when t h e k e l p p l a n t s were p r e s e n t . F i g u r e 22 i s a composite of p r e v i o u s l y p r e s e n t e d f i g u r e s which i l l u s t r a t e s t h e c l o s e c o r r e l a t i o n between t h e abundance of net caught f i s h and 45 the presence of kelp. Nettings during the period from October,1973 to April,1974 did not y i e l d any f i s h from those locations netted during the rest of the study (Figure 22). Fish i n the s i z e range 201 - 250 mm were uncommon at the kelp bed throughout the study. In addition to the study kelp bed, a second area of consistent f i s h occurrence was monitored f o r the duration cf the study. This location was a sloping area, immediately to the southeast of the study s i t e , composed of uneven, large (1.0 - 3.0 m diameter) boulders extending 2.4 -9.1 m i n depth and meeting the same sand f l a t which fronted the kelp bed area (Figure 23). Seasonal abundances of f i s h at t h i s area showed an approximate inverse co r r e l a t i o n with the presence of f i s h at the kelp bed (Figure 24). This c o r r e l a t i o n was more apparent for 30 - 100 mm f i s h than for 101 - 100 mm f i s h . ( i i ) Daily: Considerable variation was evident i n the numbers of f i s h seen on any given day or series of days. This variation existed within larger scale changes i n f i s h abundance at any location and was present at both high and low l e v e l s thereof. Experimental work conducted during the project must be considered in l i g h t of t h i s variation. A more detailed treatment of variation i n abundance i s included in section 3.7 (P. 57). 46 NTT CAPTURES 1373-1374 30-10? M-M« f £ J CAPTURES 1S73-1S74 101-150 M-M- Kelp p r e s e n c e BO- TOE NTT CAPTURES 1373-1374 151-200 M-M- 9S.J 80-. io-. Ketp pre'sence Kelp p r e s e n c e • t -I 1 ^ 1 1 J U A J 5 t O : t O C E A f E W t f U V _N 1373 1 3 7 4 TOE NET CAPTURES 1373-1374 E01-25O M-M- SO*. 40-. 35-1 fa E E . . 1 SO- 15-1 •4. 1 1 1 1 1 1 1 1 1 1 1 1 H 1 J U / U S C O C N O C E J A F E K A A P l ^ - M J J AU 1373 1S74 - I H 1 1 1 1 1 H 1 1 1 1 TOE J U A U S E 0 C N 3 I X ^ F E M A A P M Y _ N 1 3 7 3 1 3 7 4 TIME F i g u r e 22 C o i n c i d e n c e of k e l p presence and f i s h c a p t u r e  FISH ABUNDANT AT RCCK SLOPE 30-100 MM FISH ASLN3ANZE AT ROCK 5LCPE 101-150 M M b TIME - *6 1 1 1 1 -+* H f c ^ H 1 t- ND CE JA FE MA AP MY J N J U A L I 1S73 1S74 TIME FISH ABLMWCE AT ROCK SLOPE 151-500 MM FISH ABLN3AJCE AT ROCK 5LEPE 331-550 M M 53' 40- S 3 0 1 M b 30. JJO- 1 I - E 1 1 1 1 1 1 NO DE JA FE MA AP MY J N J U AU SE 1S73 1H74 TIME Observed abundances o f f i s h at tha rock s l ope 49 ( i i i ) D i e l : S. jelanop,s juveniles undertake d i e l migrations throughout the immediate v i c i n i t y of the kelp bed. The extent of these migrations varies, often extensively, between d i f f e r e n t si z e classes of f i s h but the i n i t i a t i o n , duration and completion remain r e l a t i v e l y consistent. The lengths of the migrations are cl o s e l y related to the size of the f i s h involved. Size-class d i s t r i b u t i o n graphs for 1973 and 1974 (Figures 25 to 27) establish cumulative t o t a l s of in s i t u nocturnal and diurnal positions of the f i s h e s , using the kelp bed as a frame of reference. Negative and positive numerals on the abscissa correspond to positions (in metres) shoreward and seaward from the outside of the bed, respectively. S t a t i s t i c a l analyses (Table IV) of the p o s i t i o n a l abundances of the siz e classes of the f i s h show s i g n i f i c a n t l y greater numbers of f i s h inside the bed than outside. In 1973 this s i t u a t i o n existed both d i u r n a l l y and nocturnally. In 1974 the d i s t r i b u t i o n cf the f i s h showed an al t e r a t i o n of habitat u t i l i z a t i o n by the larger size classes; i n thi s year, 30 - 100 mm f i s h showed a consistent association with the kelp bed, both nocturnally and d i u r n a l l y . Fishes of sizes 101 - 150 mm and 151 - 200 mm displayed a d i e l t r a n s i t i o n such that s i g n i f i c a n t l y higher numbers of f i s h were present outside the bed diu r n a l l y . Conversely, the nocturnal d i s t r i b u t i o n patterns were the same as i n 1973. Observations indicate that the inward migration of f i s h takes place before sunset and, i n a s i m i l a r fashion, the outward migration occurs a f t e r sunrise. No d i f f e r e n t i a l timing of the migration was noted between the two size classes. - i d ' -UJ' -a* -b- -A. -ti.' o« £• A' B.» B» 10» 12• Inside Outside Figure 25 Cumulative nocturnal and diurnal observations of fish position. 30 - 100 BD fis h 51 Inside Outside Cuoulative nocturnal and diurnal observations of f i s h position. 101 - 150 nn fish 52 50- 40.1 30.1 EO-I 10.1 SIZE CLASS DI5TN' 1373 151-200 m + Diurnal x Nocturnal -15»14. -12. -10. -B- . -4» 0« £• 4« 6» B» ID- IH- 14.15. 40- 30-1 20- 10.1 SIZE CLASS DI5TN. 1SGM ±51-200 MM + Diurnal x Nocturnal •X-X- -15-14• -12« -10. -B. -S- - 4 . Inside 4« 6« B« 40 « 12' 1 4 ' 1 S » Outside Figure 27 Cuaulative nocturnal and diurnal observations of f i s h postion. 151 - 200 BB f i s h 53 TABLE IV S t a t i s t i c a l comparison of d i e l positions of the cumulative t o t a l s of f i s h observed 1973 Size 30-100 mm 101-150 mm 151-200 mm Day I/O 1412*/1003 132*/45 118*/2 Night I/O 379/329 (+1m) 400*/308 14*/2 9/3 (+1 m)10*/2 D i e l s h i f t NO No No 1974 — + ~ Size Day I/O Night I/O Diel s h i f t 30-100 mm 101-150 mm 151-200 mm 4449*/1844 25/381* 13/105* 280*/37 191*/7 14/8 ( + 1 m) 18*/4 No Yes Yes (+1 m) - data includes those f i s h at +1.0 m as being inside the bed. * - s i g n i f i c a n t l y greater (p<.05) I - inside the kelp bed 0 - outside the kelp bed 54 3.6 Environmental correlates of d i s t r i b u t i o n The diurnal d i s t r i b u t i o n of 30 - 100 mm f i s h was consistent, i n that higher numbers of f i s h were consistently found inside, rather than outside the bed. The observations of f i s h inside the bed were further analyzed to determine i f any smaller scale migrations may have occurred and to determine i f the water column was being exploited i n any d i f f e r e n t i a l fashion by the various s i z e classes of f i s h . Figure 28 i l l u s t r a t e s the d i s t r i b u t i o n of a l l f i s h under conditions of 2.0, 2.5, 3.5, 4.0 and 8.0 metres v i s i b i l i t y . Data on the times, t i d a l heights and meteorological conditions on each occasion supplying v i s i b i l i t y - d i s t r i b u t i o n data, are presented i n Table V. E f f o r t s were made to observe the d i s t r i b u t i o n patterns under approximately eguivalent conditions, There was no s i g n i f i c a n t difference i n the average height of the f i s h i n the water column, nor was there any difference among the size classes - either within each sampling occasion or among di f f e r e n t ones. 55 Changes i n f i s h p o s i t i o n with water c l a r i t y 56 TABLE V Environmental conditions on each date supplying data for v i s i b i l i t y - d i s t r i b u t i o n analysis j ; , 1 ; ! 1 Date jMeteorology I J, 1 27/VII/74I Clear,sunny I 25/VIII/74J " ! 28/VIII/74| " I 10/71/74 | " I 1/IX/74 } " V i s i b i l i t y Tide 8.0 m I 1.80 m 115:00 4.0 m I 2.25 m | 16:00 3.5 m J2.13 m |13:50 2.5 m 12.04 m I15:00 2.0 m 12.01 m 116:30 Time A second set cf environmental correlates with f i s h d i s t r i b u t i o n a l patterns was that of nocturnal illumination and current magnitude. This influence was shown primarily at the rock slope, since t i d a l range had l i t t l e e f f e c t on currents at the study kelp bed (Figure 12). Fish appeared to exhibit contradictory phototactic responses under apparently s i m i l a r i l l u m i n a t i o n ; on moonless nights, f i s h could be found, on dif f e r e n t nights, to be either down in rock crevices or up i n the water column. Further observation suggested that the magnitude of the current i n the area may have been influencing the f i s h ' s response to l i g h t . Table VI presents the r e s u l t s of laboratory experiments examining the influence of rheotaxis upon phototaxis. The presence of both phototaxis and rheotaxis was f i r s t established and was subseguently followed by the introduction of a current into the phototactic experiment to determine i f any behavioural modification was induced from the observed 'normal' response. Results indicate an overriding 57 ef f e c t of current on the 'normal 1 positive phototaxis, such that current of s u f f i c i e n t intensity w i l l negate the phototaxis exhibited by the f i s h . The photonegative response indicated i n the table refers to movement by the f i s h away from the l i g h t , which i s associated with t h e i r movement toward the current. TABLE VI I n i t i a l conditions, manipulations and res u l t s of experiments examining the phototaxis of Sebastes melanojas and the reversal of t h i s response generated by current changes I Date 21/1 22/1 1/11 2/II 11/II 18/II 1 V I I I No. | I n i t i a l Fish| Light Phototaxis H +- I I n i t i a l |Current 2 2 2 2 4 4 4 1441.27 lux|773 1/hr 1441.27 " |773 " 1441.27 | 0.11 1441.27 | 172. 16 J212.94 |773 | 773 |773 | 773 |773 Change in Light -269.00 lux -269.00 -269.00 + 4.09 -269.00 -172.05 -176.35 Besponse +photo •photo +photo +photo +photo + p hoto +photo Influence of Bheotaxis Date No. | I n i t i a l | I n i t i a l J Change in | FishJ Light |Response| Current | Response ; .|_ H f- H 7/ 1 1 2 | 0.05 lux| +photo 1+2319 1/hr ! +rheo/- photo | 3/II 1 2 1441.27 " I •photo 1+1546 ti 1 +rheo/-photo J 11/ 1 1 | 4 1441.27 " \ +photo | +773 1 +rheo/- photo | 11 / 1 1 1 4 I 0.56 " I •photo t +773 n 1 +rheo/~ photo J 18/II | 4 I 172.16 " I +photo | +773 1 +rheo/-photo | 18/II | 4 |172.16 " I •photo | +773 ii 1 +rheo/- photo j J.. ± .... _ _ J, .x +photo - photopcsitive response +rheo - rheopositive response 3.7 F i d e l i t y and s u a n t i f i c a t i o n of association (i) The experiment involving the establishment of a small group of plants 30 m distant from the kelp bed was successful to 58 the extent that the juvenile S. melanosis were observed among the plants diur n a l l y , where none had been noted in the area previously, however no f i s h were observed nocturnally. The extension of one segment of the bed margin by 8 m served to extend the contiguous d i s t r i b u t i o n of f i s h normally associated with the bed. No differences i n behaviour or abundance of f i s h were noted, concerning either those f i s h at the 'new' bed margin, or those at the a r t i f i c i a l l y established bed, i n r e l a t i o n to those observed within the natural bed. Tracking of f i s h with fluorescein tags indicated that the association of the f i s h and the kelp bed was r e l a t i v e l y intimate. A t y p i c a l tracking record i s i l l u s t r a t e d i n Figure 29. Some cf the tracked f i s h displayed wide ranging forays (+15 m) but, generally, maintained a close enough association with the bed such that they could return to i t when rapid advances toward them were made. Figure 30 i l l u s t r a t e s numbers of f i s h and dates of the transport of tagged f i s h from the study s i t e . Transplants were performed to test the f i d e l i t y of the association between the f i s h and the kelp bed as a habitat. These experiments examined the f i s h ' s a b i l i t y to return ('home*) to a s i t e of i n i t i a l capture. A s t a t i s t i c a l analysis of the resu l t s of subsequent sampling f o r homing (Table VII) does not support the concept of s i g n i f i c a n t homing a b i l i t y to the s i t e of i n i t i a l capture, by these size classes of f i s h . 59 Ficjure 29 Tracking record of f i s h tagged with fluorescein tag 60 Figure 30 Transporting of f i s h and returns during f i d e l i t y experiments. 61 SiBLE VII Numbers, s i z e s and h a b i t a t s t o which S e b a s t e s melanojas were t r a n s p o r t e d , t o g e t h e r w i t h t h e numbers and s i z e s o f f i s h e x h i b i t i n g homing b e h a v i o u r i — — r i - X | D a t e | No. o f j S i z e | T r a n s p o r t | No. | i i F i s h | Range | H a b i t a t | R e t u r n e d | t _ j ...., . _ ...... i . _ i ., „. ,,„ i 1 X l 1 i I 18/VI/74J 7 | 118-123 mm Jopen water J 0 1 | 25/VI/74J 8 J 123-144 mm jopen w a t e r | 1-144 mm | j 4/VII/74| 4 1 134-191 mm | k e l p bed | 0 | |18/VII/74| 4 1 120-151 mm | r o c k bottomJ 0 i |25/VII/74J 7 | 110-160 mm | k e l p bed | 1-149 ram \ ! _! [_ I [ . _.. . J ( i i ) In g e n e r a l , t h e e x p e r i m e n t a l work i n v o l v i n g t h e h a b i t a t f r a m e s c e n t r e d on t h e u p r i g h t Frame I , T h i s was b e c a u s e t h e f i s h were n o t a t t r a c t e d t o Frame I I as w e l l as t o Frame I ; abundance o f f i s h a t t h e f o r m e r was u n i f o r m l y an o r d e r o f m a g n i t u d e l e s s t h a n a t t h e l a t t e r . The r e s u l t s p r e s e n t e d , t h e r e f o r e , r e f e r o n l y t o Frame I d a t a . T a b l e V I I I d e t a i l s i n f o r m a t i o n on t h e l e v e l s o f s h e l t e r p r o v i d e d a t t h e f r a m e and t h e numbers o f f i s h o b s e r v e d d u r i n g e a c h i n t e r v a l o f t h a t l e v e l ( F i g u r e 3 1 ) . F i g u r e 3J F i s h a t Frame I a t 14.2 m 2 and 33.2 m2 l e v e l s o f s h e l t e r 63 TABLE VIII Levels of shelter and f i s h associated with Frame I, together with an analysis of the variance in these numbers i n r e l a t i o n to changes in the shelter provided r T T r i 1 | Date j Level Fish at] Fish at jProportion off i lof Shelter 1 Frame | kelp bed I f i s h at Frame) j j j . -„ _ T i • j -1 11 V v i 23. 7 m2 J 3 • I 8 1 0.27 I I20/VII j II 125 | 373 ! 0.25 | |20/VIIII II 3 I 13 ! 0.19 | i22/VIIIj II 156 ! 138 ! 0.53 | J 24/VIIIJ 33.2 m.2 | 125 | 213 ! 0.37 | |25/VIII} • i 80 j 336 ! 0.19 I |27/VIIIj i i 175 | 196 ! 0.47 | | 2 8 / V I I I J n 181 373 0.33 | I 1/IX | II 7 ! 523 ! 0.01 J" I 2/IX | i i 55 169 ! 0.25 1 I 3/IX | 14.2 m2 | 10 120 S 0.07 | I 4/IX j II 20 292 I 0.06 | | 5/IX | II 85 283 I 0.23 | 4 , i j . _ _ _ i i . i i i r ; T I i |Source of | Degrees of 1 Sum of j Mean t • F' 1 j Variation t Freedom |Sguares j Sguare | S t a t i s t i c J 4 J 1 J | j 1 J J J J j Among I 2 1 o. 61 | 0. 30 | 16.67** J i Within 1 10 1 o. 22 | 0. 018 1 1 j Total 1 12 1 o. 83 | ! ! L j J . - L. . J i 64 The numbers of f i s h at the frame are presented as the proportions of the t o t a l number of f i s h seen on the observation day. The transformation of the raw data into t h i s standardized form was necessary tc compensate for the large inherent v a r i a b i l i t y i n the numbers of f i s h observed on any given day. A transformation of t h i s nature bears the j u s t i f i a b l e assumption that both the kelp bed and the habitat frame draw upon the same •universe' of f i s h to populate t h e i r environs. The r e s u l t s of a single c l a s s i f i c a t i o n analysis of variance {ANOVA) for the three l e v e l s of shelter are also included i n the table. The *F* s t a t i s t i c r esulting from the ANOVA (16.67) indicates that the variance in the numbers of f i s h observed under each shelter treatment i s s i g n i f i c a n t l y accounted for by the changes i n the treatment, rather than by factors outside the experimental design. 65 4. DISCUSSION 4.1 G e n e r a l d i s t r i b u t i o n The use o f k e l p beds by t h e f i s h s h o u l d be examined i n r e l a t i o n t o i t s t o t a l g e o g r a p h i c and b a t h y m e t r i c range. The g e o g r a p h i c d i s t r i b u t i o n of S e b a s t e s melanops was not d e l i m i t e d by i t s d e s c r i b e r ( G i r a r d 1856), The f i r s t major range statement b e i n g made by Jo r d a n and Evermann (1898:1783), who d e s c r i b e d the d i s t r i b u t i o n as e x t e n d i n g from "...Monterey t o Kadiak £=Kodiakj, most abundant n o r t h w a r d ; v e r y abundant a t S i t k a . . . a t San F r a n c i s c o , much l e s s common th a n S. my.stijrus; about Humboldt Bay much more common b e i n g the most abundant f o o d f i s h . " , The known d i s t r i b u t i o n a l l i m i t s have been extended o n l y s l i g h t l y s i n c e t h a t t i m e . M i l l e r and Lea (1972:96) d e s c r i b e t h e range as e x t e n d i n g from P a r a d i s e Cove [ C a l i f o r n i a ] t o Amc h i t k a , A l a s k a . . , " . A s i m i l a r s i t u a t i o n e x i s t s r e g a r d i n g the depth range. E a r l y papers i n f e r t h a t t h e s p e c i e s i s a s h a l l o w water form; t h e i n c r e a s i n g depth range r e p o r t e d i n s u c c e e d i n g y e a r s r e f l e c t s an i n c r e a s e d s a m p l i n g e f f i c i e n c y and e f f o r t r a t h e r than the t h e abundance o f the s p e c i e s a t t h e depths i n v o l v e d . The c u r r e n t d e l i m i t a t i o n of depth i s p r o b a b l y an a c c u r a t e e s t i m a t i o n o f the t r u e b a t h y m e t r i c range of the s p e c i e s , s i n c e s u f f i c i e n t e f f o r t has been expended i n deeper w a t e r s but has produced no specimens o f S. melanojas. The r e p o r t e d ( M i l l e r and L e a , 1972) depth range (3 - 92 m), when c o r r e l a t e d w i t h t h e m i c r o g e o g r a p h i c range o f the f i s h , l e a d s t o a d e s c r i p t i o n o f f i s h ' s d i s t r i b u t i o n (as an a d u l t ) as b e i n g c l o s e l y a s s o c i a t e d w i t h the c o a s t a l w a t e r s . A ma n u s c r i p t c o m p i l a t i o n , of t h e r e s u l t s o f c a t c h s u r v e y s ( N i s k a , 1973) on S. melanogs shows a mode of abundance 66 of adults from 0 - 50 m deep i n areas from 1 - 10 km from the coastal region. An e a r l i e r publication by Alverson, Pruter and fionholt (1964) indicated a much deeper mode of abundance (92 - 181 m) than the Oregon report. Several features of the e a r l i e r study should be considered when assessing the d i s t r i b u t i o n a l patterns of the adults: f i r s t l y , the sampling e f f o r t was considerably higher i n the 9 2 - 181 m depth range; secondly, abundances were gauged by the freguency of occurrence i n t o t a l trawls; and, f i n a l l y , trawling was done primarily during the winter months. An increased sampling e f f o r t might have indicated greater abundances in shallower water. The use of a freguency of occurrence measure masks abundances. With regard -to t h i s point, the highest freguency of occurrence and the greatest y i e l d of the species (by weight) did not occur at the same depth range; the maximum y i e l d occurred at shallower depths. The seasonal nature of the f i s h ' s movements may indicate that the reports do not represent d i s t i n c t differences i n the modes of abundance. Alverson (1960) has postulated, on the basis of catch data, that S. alutus Jordan and Gilbe r t undergoes a seasonal migration, moving into deeper water during the winter. In view of the large numbers of demersal f i s h which undergo such a seasonal migration, i t i s probable that S. melanojjs follows s u i t , this may account for the apparently d i s t i n c t d i s t r i b u t i o n s in the two reports. The f i s h i n g areas (Figure 14) are generally low to moderate r e l i e f exposed segments of coastline or c l o s e l y adjacent to them. Commercial catches of the f i s h r e f l e c t r e l a t i v e l y low abundance of the adults in most areas (when compared to S. 67 alutus and S. £i;nnic[er Jordan and G i l b e r t , or the other f i s h most abundant i n the same hauls with S. melanoo_s) accessible to commercial f i s h i n g . Dunn and Hitz {196 9) reported a spent female specimen of S. melanop,s 385 km southeast of the Alaskan peninsula, over water 2000 m deep, but in the absence of s i m i l a r offshore records of the species, t h i s must be regarded as anomalous. The inshore coastal d i s t r i b u t i o n of the species has received more attention than that of the nearshore, because i t i s a component of the sport fishery catches i n C a l i f o r n i a , Oregon and, to some extent, Washington and B r i t i s h Columbia. Hhile S. melanops r a r e l y exceeded 5% of the t o t a l inshore catch, i t ranked 12th by numbers and 8th by weight for a l l species of s p o r t f i s h landed between Oregon and Port A r g u e l l o , C a l i f o r n i a from 1957 - 1961 (Frey,1971:75). Sport f i s h catches lend corroborative evidence to the inshore nature of the species; Frey describes i t as being, "...primarily a shallow reef species...". Delacey, M i l l e r and Borton (1972) record the largest c o l l e c t i o n s of S. melanops, taken by the University of Washington, as coming from the inner reaches of Puget Sound (Colvos Passage). Adult d i s t r i b u t i o n , therefore, does not appear to be strongly associated with the occurrence of kelp beds, although populations may be within several kilometres of them. Published reports and comments by commercial fishermen, as well as personal sampling, e s t a t l i s h the inshore adult populations as being in moderate r e l i e f areas, close to the coastline or shore, often with considerable exposure to wave action. 68 The larva of the species has never been described, ahlstrom (1965), LeBrasseur (1970) and Haldron (1972) have described the broad coastal d i s t r i b u t i o n of "Sebastes species' for the C a l i f o r n i a - Eaja, northeast P a c i f i c and Oregon B.C. areas, respectively. Their results d e f i n i t e l y show that the l a r v a l d i s t r i b u t i o n has a strong coastal or inshore (<914 m i n depth) component. The highest abundances of Sebastes species larvae, excepting seamount stations, were found within 10 kilometres of the coastline, Published accounts of the d i s t r i b u t i o n and abundance of juveniles are few, i f any; I have been unable to locate any reference which treats the d i s t r i b u t i o n a l aspects of the younger l i f e stages of the species in anything except g u a l i t a t i v e form, Hubbs and Schultz (1933) described a form related to S. ffi«lano£s based upon 5 specimens obtained in a salmon trap, in 1926, at the mouth of the Columbia River, They designated the new species as Sebastodes [-Sebastes] columbianus and d i f f e r e n t i a t e d i t from Sebastodes melanges on the basis of eye diameter, colour, and body configuration. The meristic counts published overlapped with those of S. melanojas. The specimens employed in the description of S. eglumbianus were a l l over 400 mm TL, yet the authors stated i n t h e i r diagnosis of the species that "...young not occurring i n tide pools of reefs.", whereas the young of S. melano_ps were described as "...developing i n t i d e pools."(Hubbs and Schultz,1933:21). The point of s i g n i f i c a n c e i s that, in Barkley Sound waters, the young of S. jelano^s are r a r e l y , i f ever, found in tide pools. The form described by Hubbs and Schultz was reduced to subspecific status 69 by Alverson and Welander (1952) for Washington and B.C. waters. P h i l l i p s (1957), however, does not designate any subspecific forms of S. melanoDS, nor do any of the C a l i f o r n i a works following his paper, e.g., Bitz (1965) or M i l l e r and Lea (1972). Specimens of B r i t i s h Columbia forms have been uniformly described as Sebastes melanges, and I follow t h i s practice for the Barkley Sound forms. 4.2 Barkley Sound d i s t r i b u t i o n The f i r s t record of the species i n Barkley Sound was reported by Evermann and Goldsborough (1907) who described a specimen taken by the United States Fisheries Commission steamer Albatross on September 23,1888. This record i s guestionable because the station records of the Albatross do not indicate that i t was i n Barkley Sound on t h i s date. My sampling within Barkley Sound indicates a macro- d i s t r i b u t i o n a l pattern correlated with the size of the f i s h . No data are available which allow determination of any s i m i l a r patterns within the coastal range of the adults susceptible to commercial f i s h i n g , Commercial fishermen of the Bamfield region attest that, while the adults are occasionally caught i n the inner parts of Barkley Sound ( S a t e l l i t e Passage, Dodger Channel) the largest specimens of the species are caught past the mouth of the Sound. These reports corroborate the r e s u l t s of the sampling of t h i s study; however, they should be interpreted with caution for two reasons. Fishing vessels of the Bamfield region are salmon t r o l l e r s and are, b a s i c a l l y , upper water column samplers; and fishermen describe the f i s h as 'black bass' and at 70 l e a s t two species caught at the. mouth of Barkley Sound are commonly denoted as such (S. melanops and S. s i s t i n u s Jordan and G i l b e r t ) . The l a t t e r species i s , generally, found only at the mouth of the Sound during the summer months, and appears to accompany the northward intrusion of warmer water during t h i s period. In summary, the adults of the species appear to be concentrated at the mouth of Barkley Sound, rather than being di s t r i b u t e d more uniformly, or i n a d i f f e r e n t biased fashion, throughout the area. Such a d i s t r i b u t i o n , i f maintained annually, establishes the centre of reproductive e f f o r t as being along the coastline, or s l i g h t l y farther away, i f the f i s h undergo a seasonal migration. I n s u f f i c i e n t data ex i s t to confirm t h i s , since no gravid females were taken during the study and there are no published accounts of either gravid female capture or their occurrence/distribution. Results of sampling in the present study show a d e f i n i t e increasing c l i n e i n the size of f i s h captured, when sampling from the head to the mouth of the Sound (Figure 19). This c l i n e i s corroborated by observational data. These data also establish higher abundances of 0, I and I I age-classes in the inside of the Sound, than at the mouth. A plausible l i f e history of the species must account f o r t h i s d i s t r i b u t i o n . The plankton tows taken in Trevor Channel and i n the Deer Group islands i n 1973-1974 showed s i g n i f i c a n t l y higher numbers of Sebastes spp. larvae in sheltered waters of islands and bays than i n open channels. Hourston (1958,1959), working i n Barkley Sound, found a s i m i l a r d i s t r i b u t i o n of juvenile herring i n 71 r e g a r d t o t h e s e two t y p e s of h y d r o g r a p h i c s i t u a t i o n s , and p o s t u l a t e d t h a t such a d i s t r i b u t i o n was a c h i e v e d through d i s p e r s a l from the spawning grounds ( p r i m a r i l y on t h e n o r t h w e s t s i d e of -the Sound) and g r a d u a l a c c u m u l a t i o n o f the j u v e n i l e s i n t h e s e s h e l t e r e d a r e a s . He c o n c l u d e d t h a t such d i s p e r s a l was n e i t h e r p a s s i v e , w i t h the c u r r e n t s , nor was an a c t i v e s e a r c h i n g on the p a r t of t h e j u v e n i l e s f o r such e n v i r o n m e n t s . Hoursfon b e l i e v e d , on t h e b a s i s of s e v e r a l t e s t s o f d i s t r i b u t i o n a l c o r r e l a t e s , t h a t t h e a g g r e g a t i o n s o f j u v e n i l e s were the r e s u l t of p r i m a r i l y random movement by t h e f i s h ; movement which d i m i n i s h e d when a s u i t a b l e environment was found. The a t t r a c t i v e n e s s of t h e s h e l t e r e d a r e a s was tho u g h t t o be r e l a t e d t o the d e c r e a s e i n p h y s i c a l s t r e s s which t h e h e r r i n g e x p e r i e n c e d w h i l e t h e r e . He a l s o demonstrated an i n c r e a s e d abundance o f the f i s h i n the most s h e l t e r e d a r e a s of t h e bays and i n l e t s ; a r o u n d , " . . . d o c k s , l o g booms, k e l p p a t c h e s and r o c k p i l e s . " (Hourston,1959:303). The c o n c e n t r a t i o n s of Sebastes spp. l a r v a e found i n my st u d y g e n e r a l l y m i r r o r t h a t r e p o r t e d f o r j u v e n i l e h e r r i n g . The f i n e - s c a l e d i s t r i b u t i o n o f t h e l a r v a e may or may not have r e f l e c t e d the same p a t t e r n , but w i t h r e g a r d t o t h e k e l p p a t c h e s , i t was i m p o s s i b l e t o determine t h i s because t h e new y e a r * s growth o f k e l p s p o r o p h y t e s was i n s u f f i c i e n t t o e s t a b l i s h v i s i b l e k e l p p a t c h e s . A l t h o u g h t h e abundance o f l a r v a e was g r e a t e r i n many a r e a s which l a t e r c o n t a i n e d k e l p beds, t h e r e was a t l e a s t one l a r g e bay ( f i o g u e f e u i l B a y , F i g u r e 3) which s u p p o r t s both l a r g e k e l p beds and S. melanop_s p o p u l a t i o n s d u r i n g t h e summer, w i t h i n which v e r y few Sebastes spp. l a r v a e were t a k e n . The 72 d i s t r i b u t i o n of S. mej.anoj)s larvae can only be extrapolated from that of observed specimens of Sebastes spp. The size of the juveniles of S. melanogs appearing In the kelp beds i n mid-May indicates that the time of spawning for t h i s species agrees with the February Puget Sound spawning records (Delacy et al.,1964), rather than with the A p r i l Vancouver Island reports (iestrheira et a l . , 1 968) . The segregation between the observed abundances of adults and those of larvae may be explained by physical oceanographic factors. Doe (1952) found high surface transport out of Barkley Sound on the west side of the Sound during the spring. This surface transport was primarily a r e s u l t of freshet conditions i n the Toguart and Somass r i v e r s , A corresponding inward flow of water took place on the east side of the Sound and i n deeper water on the west side, during t h i s period. It i s plausible that S. melano^s larvae, i f extruded at the c o a s t l i n e , could be passively carried into the Sound with these currents. Observational samples show S. melanops juveniles, es p e c i a l l y 30 - 100 mm f i s h , to be more abundant in beds of J2il££2£istis i n t e c [ r i f o l i a than i n beds of the more exposed Nejceocystis luetkeana. Higher numbers of f i s h were found i n M. i n t e c j r i f o l i a beds in sheltered waters (Ross I s l e t s , Eoguefeuil Bay) than in beds of the same plant i n more exposed locations (2nd Beach, Cape Beale). These observations, when coupled with the c l l n a l variation i n size of sampled f i s h , lead to the conclusion that the observed d i s t r i b u t i o n of f i s h i s related to the degree of exposure of the habitat or, more generally, the wave stress imposed upon the f i s h . This 73 c o n c l u s i o n may not r e f l e c t t h e o n l y cause and e f f e c t mechanism a t work but i t i s d e f i n i t e l y a major component i n t h e d e t e r m i n a t i o n o f the d i s t r i b u t i o n a l p a t t e r n o f t h i s s i z e group of j u v e n i l e s . 4.3 S e b a s t e s melano£s i n M i c r o c y s t i s beds The presence of the s p e c i e s i n beds of M a c r o c y s t i s i s l i m i t e d t o t h e j u v e n i l e s i n t h a t none of the f i s h from the k e l p beds were found t o be s e x u a l l y mature. The s m a l l e s t f i s h i n the k e l p bed were 40 - 50 mm yo u n g - o f - t h e - y e a r . These f i s h would be d e s i g n a t e d as t h e 0 - I a g e - c l a s s and would i n c l u d e t h o s e f i s h up t o 100 mm. The p o p u l a t i o n o f the f i s h a t the s i t e i n c l u d e d t h r e e o r , i n f r e g u e n t l y , f o u r age- c l a s s e s {Table I I ) . The abundance of t h e f i s h a t the s i t e was r e a s o n a b l y c o n s t a n t on an annual b a s i s f o r t h e ages I I to IV f i s h . Major f l u c t u a t i o n s i n the p o p u l a t i o n were a r e s u l t o f y e a r l y r e c r u i t m e n t by the 0 - I age f i s h ( F i g u r e 1 8 ) . The r e c r u i t m e n t and growth of t h e s e f i s h t o a s i z e which was c a p a b l e o f b e i n g tagged i s r e f l e c t e d i n t h e sudden i n c r e a s e i n e s t i m a t e s o f p o p u l a t i o n i n August,1974. The r e c r u i t m e n t o f the s e i n d i v i d u a l s was o b v i o u s i n o b s e r v a t i o n s b e g i n n i n g i n June of the year but i t was not p o s s i b l e t o t a g them u n t i l e a r l y a u g u s t , due both t o t h e s m a l l f i s h (<80 mm) bei n g u n s u s c e p t i b l e t o net c a p t u r e and unable t o s u p p o r t a t a g . The c l o s e agreement between p o p u l a t i o n e s t i m a t e s computed i n l a t e f a l l , when t h e k e l p bed was d e g e n e r a t i n g and i n the l a t e s p r i n g , when t h e new y e a r ' s s p o rophyte growth began, i n f e r s an a p p r o x i m a t e l y c o n s t a n t p o p u l a t i o n o v e r w i n t e r i n g a t the s i t e . These estimates may indicate a probable low value of natural mortality over winter, as well as a minimum residency of tagged in d i v i d u a l s of at least one year. The s i m i l a r i t y of these estimates may also indicate that mortality, followed by immigration was occurring; however, t h i s would necessitate d i f f e r e n t i a l mortality cf untagged f i s h i n order to maintain s i m i l a r estimates, and I think t h i s s i t u a t i o n u n l i k e l y . The i n i t i a l increase in the population estimate (by both methods) i n early 1974 i s a r e s u l t of the previous year's juveniles becoming accessible to the tagging program. The large increase in the population estimate in August,1974 i s not mirrored in 1973 because very few 0 - I juveniles were tagged in 1973 and, the recruitment of t h i s age class of f i s h was higher i n 1974. A t h i r d possible factor responsible for t h i s increase was the addition of the two habitat frames at the s i t e i n t h i s year. The degree to which these may have increased the resident population i s unknown, however an influence i s inferred by the fa c t s that the increase i n the population was almost exclusively through t h i s s i z e c l a s s and that these were the f i s h which were attracted to the habitats. A degree of learning by the f i s h i s indicated by the consistently lower estimates generated using observational data over those using recapture data. A higher proportion of tagged vs. untagged f i s h were observed than were represented i n the net captures. This i s most probably accounted for by net avoidance on the part of tagged f i s h and concomitant decrease i n recaptures. Observational data c o l l e c t i o n did not necessitate capture and handling and the sampling technigue was not biased 75 toward untagged in d i v i d u a l s . In l i g h t of these considerations, I f e e l that the estimates generated using the observational data are the more accurate of the two. In addition, the a v a i l a b i l i t y of the tagged f i s h to observation, as opposed to recapture, i s responsible for the lower degree of f l u c t u a t i o n in the observation estimates. 4,4 Diet An examination of the diet of those fishes present at the s i t e leads to the conclusion that the population i n t h i s area d i r e c t s the majority of i t s foraging a c t i v i t y to the water column, rather than to the benthos. The clupeiform f i s h and mysids which form the dominant portion of the diet are water column inhabitants. Neither of these items were found to be in higher abundance inside the kelp bed than outside. Clupeiform f i s h , of the size found in the stomach contents, were never observed inside the bed, a l b e i t they maintained an intimate s p a t i a l r elationship with i t at times. In the few instances when S. j§lano£s were actually observed feeding on clupeids, the situations were very s i m i l a r . A school of Clup_ea hargngus o a l l a s i Valenciennes would pass close to the bed and an i n d i v i d u a l S. melanojjs would dash out and capture one of the small herring. On every occasion, the i n d i v i d u a l capturing the herring had pieces of the uningested herring torn from i t s mouth by conspecifics. Some alternation in the use of trophic resources on a seasonal basis, s i m i l a r to those described by Gotshall et a l . (1965) i s evidenced i n Figure 21. While some overlap 76 e x i s t s , there i s a segregation between the periods of maximum occurrences of mysids and clupeids in the stomachs of the f i s h . I t i s known that the young-of-the-year herring appear near kelp beds i n late May (Hourston,1958,1959; Marliave, personal communication). Mysid blooms have been noted i n 1974 and 1975 to occur i n early May. These times of occurrences correspond generally to the times cf occurrences of these diet items i n the f i s h ' s stomachs. I do not have guantitative data on the abundances of these two primary prey items i n the environment and i t i s not possible to construct any index of trophic s e l e c t i o n such as those s i m i l a r to Ivlev's (1961) ' E* index, e.g., frame (1974) or Gerald (1966). The anlysis of the diet data d i f f e r s from previous diet analyses performed under a s i m i l a r data handicap. I have t r i e d to eliminate the s u b j e c t i v i t y of the methods of Tester (1932) and Hynes (1950) as well as avoid a sole reliance on the occurrence of diet items (Quast,1968), The dominance data employed are conservative estimates of the contributions of various diet items rather than optimistic ones such as results from an analysis based on occurrence of items alone. A more detailed analysis, such as that of Carr and Adams (1973) was not possible, while a l e s s detailed one (Fritz,1974) did not y i e l d s u f f i c i e n t information. The analysis i n my study attempts to improve on the basic occurrence/volume presentation (Heufcach et al.,1963; Gotshall et al.,1965). No experiments on the feeding behaviour of Sebastes melanogs were conducted. I t must remain unknown, on the basis of currently available information, whether the abundances of 77 items i n the diet represent preference or s p e c i a l i z a t i o n (Bryan and Larkin ,1972; Landenberger,1968; Hood,1968) or a passive response to d i f f e r e n t i a l abundances of prey items i n the environment (Gerald,1966; Murdoch,1968). 'Switching 1 (after Murdoch, 1968; B o i l i n g , 1965; Tinbergen, 1960) by S. j§lano£j= would re s u l t in a similar record of diet item occurrence i f such a seasonal a l t e r a t i o n of mysids and clupeid f i s h had occurred; however the studies of Murdoch (1968) and Landenberger (1968) indicate that even sophisticated experimental design w i l l not prove the existence of such switching. Strong preferences by predators tend to negate d i f f e r e n t i a l abundances of prey items i n the laboratory and preference testing i s generally inconclusive when the predator i s faced with multiple prey items. In addition, Holling (1959) found that predators would occasionally select ncn-preferred diet items even when the preferred item was abundant. Increasing the level s of the preferred item even further yielded an increasing u t i l i z a t i o n of the alternate diet items. While the s i z e , appearance, habits and taste of the prey may act to govern their abundance in the diet (Allen,1941), Gerald (1966) found good c o r r e l a t i o n between forage r a t i o s of diet items and t h e i r abundance and/or a v a i l a b i l i t y in the f i e l d . The l a t t e r indicates a purely passive feeding response on the part of the predator, when faced with d i f f e r e n t i a l abundances of diet items. I use 'passive' i n the sense that the alternate prey i s eaten merely because i t , ".. . o f f e r s a s u f f i c i e n t l y higher rate of reward..." (Croze,1970:79), rather than actually connotating greater preference, i n the sense of Murdoch (1968). 78 Although i t i s impossible to determine the degree of s e l e c t i v i t y , i f any, which the f i s h exhibit toward t h e i r t o t a l diet spectrum, an analysis of the r e l a t i v e contribution of the various diet items can be made. The s t a t i s t i c a l analysis of the volume - based dominance data i n f e r s a general reliance by the species on clupeids and mysids for the vast majority of i t s energy input during i t s presence i n the kelp bed. The presence of mysids as the dominant item for 101 - 150 mm f i s h , while the other two size classes exhibit clupeid dominance, warrants comment. F i r s t l y , the sample size for the 30 - 100 mm f i s h i s very small for a positive indica t i o n of major diet input. Secondly, those herring eaten by the smallest f i s h were l a r v a l or juvenile forms and thus, probably not a t t r a c t i v e to the larger f i s h as a diet item. For the duration of t h e i r presence in the kelp bed, f i s h of the largest size class examined (151 - 200 mm) exhibit overwhelming reliance on clupeid f i s h . while the f i s h have been shown to u t i l i z e clupeids and mysids to a greater degree than other diet items during t h e i r period of residence in the kelp bed, no evidence i s available which describes t h e i r primary diet input during the winter months, when they adopt an alternate habitat. The seasonality of their summer food sources (Hourston,1959) reguires an alternate winter d i e t . The metabolic rate of the f i s h and hence the i r feeding rate, i s necessarily smaller i n the winter months; evidence for t h i s i s both d i r e c t (temperature control of metabolic rate) and i n d i r e c t (annual checks i n scale c i r c u l u s formation). The i d e n t i t y of the winter diet i s unknown but i n consideration cf the habitat associations of t h e i r summer forage items, I would 79 assume that S. me l a nop. § u t i l i z e s p e l a g i c s p e c i e s as i t s primary energy source during the winter as w e l l . Previous work i n Barkley Sound (Druehl, Green and Leaman, unpublished data) has shown t h a t S. melanojjs i n other l o c a t i o n s u t i l i z e s sandlance (Ammody.tes hexapterus P a l l a s ) as a food source l a t e i n the summer. l a t e r work i n Ne r e o c y s t i s luetkeana beds (Leaman, i n preparation) has shown t h a t s h o a l s of 80 - 100 mm sandlance appear i n these beds i n l a t e August - e a r l y September and present a demonstrably e x p l o i t a b l e resource. 4.5 A c t i v i t i e s i n the ke l p bed The u t i l i z a t i o n c f the kelp bed as a h a b i t a t by the f i s h was s t r o n g l y s e a s o n a l as a d i r e c t r e s u l t of the s e a s o n a l i t y of the bed i t s e l f (Figure 13). The onset of sporophyte growth i n May - A p r i l was not immediately accompanied by the appearance of Sebastes melanges i n the bed. The time l a g between growth i n i t i a t i o n and the appearance of f i s h i s a f u n c t i o n of the degree of water column o c c l u s i o n by the growing p l a n t s . F i s h d i d not occur u n t i l a f t e r the p e r c e n t a g e - o c c l u s i o n had exceeded 75%. The apparent d i s p a r i t y between the appearance of the f i s h at t h i s o c c l u s i o n value and the maintenance of f i s h at lower values l a t e r i n the summer i s r e l a t e d t o the morphometry of the pl a n t throughout i t s growing season and the technigue of measurement of o c c l u s i o n . The p l a n t grows from a b a s a l h o l d f a s t and p r o l i f e r a t e s to the s u r f a c e through a graduated and continuous s e r i e s o f f r o n d s . The progress of the growth of these fronds through the water column, a l b e i t v i a i n t e r c a l a r y meristematic t i s s u e , i s analagous t o the growth cf a t e r r e s t r i a l 80 shoot. The water column i s not occluded gradually as a whole \ but progressively from the bottom to the surface. The f i s h were not present i n the bed u n t i l the plants were approximately one- half of the distance to the surface. Ihe occlusion measurements were made only 0.8 m above the substrate and were not necessarily representative of the entire water column exploited by the f i s h , which i s primarily a mid-water-column form. The maintenance of f i s h i n the kelp bed i n August - September, when the occlusion values f e l l below 60$, again r e f l e c t s the plant's morphometry and the measurement technigue. Lower laminae of the fronds degenerate i n l a t e summer resulting i n the decreased occlusion values. Upper and mid-water laminae of the plants remain viable during t h i s period (Figure 32) and continue to provide an occluded water column. The f i s h appear to be unaffected by the changes i n the lower portions of the plants. This s i t u a t i o n contrasts with the response of birds to changes i n the v e r t i c a l structure of t e r r e s t r i a l forests (Hagar, 1960; Martin,1960), wherein bird communities change both q u a l i t a t i v e l y and guantitatively with changes in the successional status of the forest. It also contrasts with the species changes associated with differences in forest foliage p r o f i l e (HacArthur and MacArthur,1961). 81 F i g u r e 32 S u r f a c e c a n o p y o f t h e p l a n t s i n l a t e A u g u s t , 1 9 7 4 D a i l y o b s e r v a t i o n s o f f i s h e s i n t h e k e l p bed were c h a r a c t e r i z e d by a l a r g e v a r i a t i o n i n t h e numbers o f f i s h s e e n , s i m i l a r t o o b s e r v a t i o n s i n C a l i f o r n i a k e l p beds ( Q u a s t , 1 9 6 8 ; T u r n e r e t a l . , 1 9 6 9 ) . T h i s v a r i a t i o n i n s i g h t i n g s r e l a t e d p r i m a r i l y t o t h e s m a l l e s t s i z e c l a s s o f f i s h due t o t h e i r g r e a t e r a b u n d a n c e . S e v e r a l f e a t u r e s may ha v e a c t e d s i n g l y , o r i n c o n c e r t , t o mask t h e a c t u a l a b u n d a n c e o f f i s h . The f o r e m o s t o f t h e s e f e a t u r e s was t h e c l a r i t y o f t h e w a t e r ; w a t e r i n w h i c h v i s i b i l i t y i s d e c r e a s e d t h r o u g h p h y t o p l a n k t o n b l o o m s , t e r r e s t r i a l r u n - o f f o r p a r t i c u l a t e d e t r i t u s , s e v e r e l y hampers o b s e r v a t i o n . I c o n s i s t e n t l y made c n l y one s e t o f c b s e r v a t i o n a l sweeps t h r o u g h t h e k e l p bed t o m i n i m i z e t h e p o s s i b i l i t y o f d u p l i c a t e e n u m e r a t i o n . O b s e r v a t i o n s made d u r i n g p e r i o d s o f 82 lowered v i s i b i l i t y were more susceptible to duplicate sightings because of the p o s s i b i l i t y of undetected movement of the f i s h to unenumerated areas. Observations made during or af t e r storms often yielded few sightings because the f i s h were sheltering in crevices, both i n and around the kelp bed. The additional time reguired to make a more thorough search of these refugia resulted i n a decrease in the t o t a l time/area observations. S i m i l a r l y , the illumination in the bed ( d i s t i n c t from water c l a r i t y ) affected my perception of the f i s h i n the water column. The variation i n sightings i s thought to be primarily a function of factors a f f e c t i n g observations^ rather than a r e f l e c t i o n of actual variation i n the numbers of f i s h present. This does not negate the fact that such variation in numbers undoubtedly occurs on a d a i l y basis. The actual variation i n the numbers of f i s h inside the bed may be an expression of the abundance of the larger size classes of f i s h , since they are known to undergo more extensive migrations than the smaller f i s h . The l o c a l d i s t r i b u t i o n of the f i s h and t h e i r d i e l a c t i v i t i e s have p a r a l l e l s i n both other kelp bed studies and i n limnological work. Limbaugh (1955) found a s i m i l a r pattern of greater abundance of f i s h at the edge of C a l i f o r n i a kelp beds. He did not, apparently, make any observations of the c l i n e s i n the abundance of fishes with position i n the kelp bed, other than noting that the juveniles of some species appeared to be more abundant i n the inshore rocky zone than inside the kelp bed. The larger size of the plants in C a l i f o r n i a and the greater depth i n which they grow introduces an added habitat complexity which i s not mirrored i n B r i t i s h Columbia kelp beds. 83 Limbaugh was able to distinguish whether species were primarily bottom, mid-kelp or canopy fishes. The shallowness of my study s i t e precluded any depth d i s t i n c t i o n of t h i s nature. Sebastes melano£_s appeared to exploit the entire water column, save for the surface layer above the thermocline (at approximately -1.0 m). Quast (1968) also distinguished u t i l i z a t i o n of segments of the kelp bed by various species, although he did not d e t a i l the smaller scale movements of i n d i v i d u a l species. Neither of these studies quantified the pattern of abundance of kelp bed forms within the bed, nor did they encompass d i e l observations. Their q u a l i t a t i v e comments about various species included an assessment of the •dependency* of the species on the kelp bed biotype but t h e i r assessment of 'dependency' was primarily based upon the the degree of crypsis i n the colouration of the f i s h . Fish showing no c r y p t i c colouration were assumed to be non- dependent on the kelp bed. S. melanogs would f a l l into t h i s category. The lack of d i e l observations in the aforementioned studies hamper the comparison between S. melanogs and the probable C a l i f o r n i a analogues, S. serranoides Eigenmann and Eigenmann, faralabrax clathratus Girard and S. saxicola ( G i l b e r t ) . These species appear to occupy the same type of habitat as S. melanops but diet analysis (Quast,1968) indicated that they forage more on benthic invertebrates than S. melanops does. High values of clupeoid f i s h occurrence in the stomach contents of the C a l i f o r n i a fishes was thought to be a function of the sampling technigue ('chumming'), rather than an expression of the normal feeding behaviour of the f i s h . The d i e l a c t i v i t i e s of S. jelanop_s are thought to be a 8U r e s u l t o f the f e e d i n g b e n e f i t s d e r i v e d from an extended d i u r n a l range and the s u r v i v a l b e n e f i t s a s s o c i a t e d w i t h the u t i l i z a t i o n of a n o c t u r n a l r e f u g i u m from p r e d a t o r s , such as Ophipdon e l g n g a t u s G i r a r d , S. j j a u c i s p , i n s i s (Ayres) , Sgualus a c a n t h i a s L i n n a e u s and Salmo a a i r d n e r i R i c h a r d s o n . D i e l changes i n gut c o n t e n t and s a m p l i n g f o r d i e t i t e m s w i t h i n t h e k e l p bed do not i n d i c a t e t h a t t h e k e l p bed i s u t i l i z e d as a f o o d r e s o u r c e base fry Se b a s t e s melanops. More r e c e n t work i n C a l i f o r n i a k e l p beds (Bray, p e r s o n a l communication) has i n v e s t i g a t e d t h e d i e l a c t i v i t i e s of O x y J u l i u s c a l i f o r n i c a Gunther, Phanerodon f u r c a t u s G i r a r d and B r a c h y i s t i u s f r e n a t u s G i l l i n terms of f o r a g i n g and h a b i t a t p r e f e r e n c e s . A c t i v i t i e s o f t h e s e s p e c i e s were det e r m i n e d from l a b o r a t o r y swimming e x p e r i m e n t s , l i m i t e d f i e l d o b s e r v a t i o n s and t h e d i e l f l u c t u a t i o n o f gut c o n t e n t s . A l l s p e c i e s were d i u r n a l f e e d e r s ; 0. c a l i f o r n i c a s h e l t e r e d by bur r o w i n g i n sand a t n i g h t . No i n f o r m a t i o n was a v a i l a b l e on t h e v m i g r a t i o n s of t h e s e f i s h . Bray has a l s o i n v e s t i g a t e d t h e d i e l a c t i v i t i e s of Chromis p u n c t i p i n n i s (Cooper) and H^£erp.rgsopon ajraentjjum Gibbons. The former s p e c i e s f e e d s by day i n t h e k e l p bed and h i d e s i n h o l e s a t n i g h t . The l a t t e r s p e c i e s s c h o o l s i n s h o r e d u r i n g t h e day and m i g r a t e s out t o t h e k e l p beds t o f e e d a t n i g h t . The a c t i v i t i e s o f H. argenteum a r e t h e c o n v e r s e o f those of Sebastes melang£s. The a c t i v i t i e s o f S. m§lano£s i n B a r k l e y Sound appear t o be analogous to thos e o f some s p e c i e s i n C a l i f o r n i a k e l p beds but i t i s d i f f i c u l t t o a c c u r a t e l y compare them because t h e i n f o r m a t i o n on the s o u t h e r n s p e c i e s i s e i t h e r of a g u a l i t a t i v e n a t u r e o n l y , o r i t i s u n f i n i s h e d or u n p u b l i s h e d . 85 Work cn coral reef fishes by Hobson (1973) elucidated their d i e l feeding migrations, characterized by movement away from the reef at night to feed and schooling near the reef d i u r n a l l y , i n response to predation pressure. This type of migration, although temporally opposite, i s s i m i l a r to that of S. melanops. except f o r the schooling behaviour. The t r o p i c a l counterparts are certain sciaenids and pomadasyids. Baumann and K i t c h e l l (1974) described d i e l feeding migrations between diurnal limnetic feeding areas and the nocturnal l i t t o r a l area i n juvenile lepomis macrochirus Raflnesgue, which correspond to the movements of the larger size classes of S. melanops but not to the smallest. In addition, the migration by L. macrochirus was primarily by the smallest juveniles (the larger f i s h remaining i n the l i t t o r a l area) and was thought to be s o l e l y related to feeding; no mention of refuge seeking i s made. With regard to the a c t i v i t i e s of Sebastes melanops, the d i e l migration of 101 - 200 mm f i s h , which occurred in 1974, was not noted in 1973. I believe that these migrations are density - associated phenomena. The abundance of the smaller (30 - 100 mm) juveniles was very much higher (approximately f i v e times) i n 1974 than i n the previous year (Figure 18) and since t h i s s i z e - c l a s s was the most intimately associated with the kelp bed, the competition f o r trophic resources i n the immediate v i c i n i t y of the kelp bed would have been concomitantly higher in that year. The larger f i s h , being r e l a t i v e l y l e s s vulnerable to predation, were able to avoid t h i s increased competition by exploiting more distant trophic resources which were unavailable to the C - I juveniles. 86 The behaviour of S, melanops has b i o l o g i c a l correlates i n terms of feeding and shelter. There are also environmental correlates of these a c t i v i t i e s . Increased water c l a r i t y r e s u l t s i n a movement of the smallest s i z e - c l a s s of f i s h deeper into the kelp bed. This response appears to be a graded response above a certain threshold l e v e l (Figure 28). D i s t r i b u t i o n of 30 - 100 mm f i s h i s centered about the edge of the bed when v i s i b i l i t y i s less than 3.5 m. Movement into the kelp bed i s i n i t i a t e d under conditions of increased water c l a r i t y . The juveniles are not c r y p t i c a l l y coloured to a great degree and the increased water c l a r i t y would increase t h e i r v u l n e r a b i l i t y to predation by visual predators, hence the inward movement with i t s concomitant increase in shelter and security. The larger size classes of f i s h do not appear to par t i c i p a t e i n t h i s r e t r e a t , r e f l e c t i n g t h e i r size-associated decreased v u l n e r a b i l i t y . Size-dependent s u s c e p t i b i l i t y to predation has been detailed for a wide variety of organisms, both aguatic and t e r r e s t r i a l (F,E,Smith, 1954; fi.L.Smith,1966; Pianka,1974) and the behaviour of S, melanops juveniles i s only one of several mechanisms which organisms employ t c escape predation on juvenile forms (crypsis, shelter- seeking, mimicry, morphological adaptations, e t c . ) . The a l t e r a t i o n of the d i s t r i b u t i o n of the f i s h through i t s rheotactic response i s another environmentally correlated facet of the behaviour of this species. The sign i f i c a n c e of t h i s behaviour i s open to speculation. The species i s apparently exchanging a degree of sec u r i t y , which i t gains through i t s association with the kelp bed or rock slope, for a benefit derived from i t s hovering postion in the t i d a l currents. 87 S e v e r a l e x p l a n a t i o n s may be p r e s e n t e d f o r t h i s b e h a v i o u r . Given t h e f a c t t h a t t h e s p e c i e s i s p r i m a r i l y a water column f o r a g e r , i t may s i m p l y be o p t i m i z i n g i t s f o r a g i n g o p p o r t u n u t i e s ; t h e r e s p o n s e may be t h e e x p r e s s i o n o f a f a c u l t y n e c e s s a r y i n the a d u l t s t a g e of i t s l i f e t o m a i n t a i n i t s p o s i t i o n i n exposed h a b i t a t s ; o r , the c u r r e n t s g e n e r a t e d may exceed the • c r t i c a l v e l o c i t y * ( P a v l o v e t al.,1972) at t h e s u b s t r a t e l e v e l , f o r c i n g t h e a n i m a l up i n t o the water column. The e x i s t i n g i n f o r m a t i o n i s not s u f f i c i e n t t o i n d i c a t e the v a l u e t o the f i s h t h a t such b e h a v i o u r i m p a r t s , but the assumption must be made t h a t i t does not e v i d e n t l y a c t t o t h e f i s h ' s d e t r i m e n t . 4.6 The n a t u r e o f t h e a s s o c i a t i o n In the a n a l y s i s o f t h e a s s o c i a t i o n of S e bastes melanops and beds of H a c r o c y . s t i s , the d a t a g a t h e r e d i n d i c a t e d t h a t t h e f i s h was u s i n g t h e bed as a p h y s i c a l r e f u g i u m , p r o b a b l y from n o c t u r n a l p r e d a t i o n . The d i e l d i s t r i b u t i o n p a t t e r n s c l e a r l y i n d i c a t e d the p r o p o r t i o n a t e i n c r e a s e i n the n o c t u r n a l u t i l i z a t i o n , e s p e c i a l l y when c o n s i d e r i n g the l a r g e r s i z e c l a s s e s . R e s u l t s of e x p e r i m e n t a l p l a n t m a n i p u l a t i o n showed t h a t t h e d i s t r i b u t i o n o f the p l a n t has a d e f i n i t e e f f e c t on t h e d i s t r i b u t i o n of the j u v e n i l e f i s h , both i n terms of e x t e n d i n g an e x i s t i n g d i s t r i b u t i o n and a t t r a c t i n g f i s h t o a new l o c a t i o n . The t r a n s p o r t i n g e x p e r i m e n t s d i d not show a s i g n i f i c a n t homing a b i l i t y on t h e p a r t o f S. melanops j u v e n i l e s , when d i s p l a c e d from t h e i r p o i n t o f c a p t u r e i n the s t u d y k e l p bed. A homing a b i l i t y may be p r e s e n t i n the a d u l t s , a f t e r the f a s h i o n o f S. f l a y i d u s ( C a r l s o n and Haight,1972) but t h i s a b i l i t y has not been 88 demonstrated f o r the j u v e n i l e s of any s p e c i e s o f Sebastes. The l a c k of r e t u r n s of t r a n s p o r t e d f i s h i n d i c a t e d that the j u v e n i l e s were e i t h e r unable to home (or had not yet developed the a b i l i t y ) o r, t h a t there was no f e a t u r e of a kelp bed t h a t was s u f f i c i e n t l y important to the s p e c i e s to warrant the development, over e v o l u t i o n a r y t i m e - s c a l e , of an a b i l i t y t o r e t u r n to a given bed. The h a b i t a t frame experiments were conducted to e l u c i d a t e what gen e r a l f e a t u r e of any k e l p bed supported the obvious a s s o c i a t i o n between the two s p e c i e s . They were designed to provide only the s h e l t e r component of the k e l p bed and to do so i n an a b i o t i c f a s h i o n , which would t e s t whether t h i s component was of s i g n i f i c a n t importance i n a t t r a c t i n g f i s h . The h i g h l y s i g n i f i c a n t response of the j u v e n i l e s t o the changes i n the s h e l t e r provided (Table VIII) c l e a r l y i n d i c a t e s t h a t the p h y s i c a l s h e l t e r provided by the p l a s t i c (and by analogy, the kelp) r e p r e s e n t s a component of the h a b i t a t which may p o t e n t i a l l y determine the numbers of f i s h present w i t h i n the environs of a given bed. The importance of the s h e l t e r component of a h a b i t a t i n a t t r a c t i n g f i s h p o p u l a t i o n s has been i n d i c a t e d p r e v i o u s l y by the p r o v i s i o n of a r t i f i c a l s u b s t r a t e s (Fujimura and Kami, 19 58; Kami,1962; C a r l i s l e , Turner and Ebert,1964; Ogawa,1966,1967, 1968; Ogawa and Onoda,1966). None of these s t u d i e s attempted to q u a n t i f y the numbers of a t t r a c t e d f i s h with the amount of s h e l t e r provided at a given s i z e of r e e f , r a t h e r , they examined v a r i o u s s i z e s of r e e f s . Ogawa amd Aoyama • (1966) d i d f i n d t h a t the p r o v i s i o n of p l a s t i c s t r i p s inhanced the a t t r a c t i v e n e s s of any a r t i f i c i a l r e e f but they n e i t h e r q u a n t i f i e d t h i s enhancement, nor manipulated the number 89 of p l a s t i c s t r i p s , Senta (1965) related the results of studies conducted i n Japan ' on the association of fishes and f l o a t i n g clumps of seaweed. The fishes found i n and around these clumps were primarily pelagic, oceanic forms and Senta regarded the fishes as using them mainly as refugia from predation. He found no re l a t i o n between the size of the clumps and the number of f i s h present but he did find that the degree of s t r u c t u r a l heterogeneity of the clumps was a major factor in attra c t i n g f i s h . In addition, he found that f i s h exhibited varying degrees of association with the seaweed, Small Sebastes inermis Valenciennes leave these seaweed clumps and move into the nearshore seaweed beds when they reach 50 - 60 mm, The response of S. • melanops•to p l a s t i c * kelp 1 p a r a l l e l s the response of pelagic f i s h noted in this study. Quast (1968) stated that the f i s h u t i l i z e d the kelp as orientation points i n the water column to establish t h e i r contact with the bottom. I do not believe t h i s i s the case with S. melanops because v i s i b i l i t y i s not related to the position of the f i s h i n the water column. The f i s h appears to be using the physical presence i n the water column as shelter rather thas an an orientation point with the substrate. Hunter and Mitc h e l l (1968) found a disproportionately large number of f i s h surrounding th e i r three-dimensional r a f t when comparing i t s size to two-dimensional r a f t s of s i m i l a r s i z e . They inferred that the size of the three-dimensional r a f t might not be as important as in a si m i l a r two-dimensional one although they employed only one size of three-dimensional r a f t . My 90 studies with three-dimensinal shelter suggest that, while a three-dimensional object i s more a t t r a c t i v e , a s i m i l a r relationship between size and abundance of f i s h e x i s t s with three-dimensional objects, as does with two-dimensional ones. The results of my studies using a r t i f i c i a l seaweed dc not i l l u s t r a t e that the amount of shelter provided by the kelp plants i s the sole cause and e f f e c t relationship governing the abundance of juvenile S. melanops present; however, they do provide proof that t h i s component of the habitat i s one to which the f i s h show a very strong in s i t u numerical response. 4.7 Significance of the k e l j D bed to the f i s h The information presented i n t h i s t h e s i s , together with published material, indicate that the association between S. melanops and M. i n t e g r i f o l i a in Barkley Sound i s almost exclusively concerned with non-sexually mature juveniles. Diet analysis does not imply a reliance by the f i s h on a food resource base which i s strongly associated with kelp beds. A s t r i c t l y b i o t i c association between these two species i s not evidenced by t h i s study. I believe that the s i g n i f i c a n c e of the kelp bed to S. melanops i s that o;f a physical refugium from predators. While feeding in the kelp bed undoubtedly occurs, observations of feeding and inference from d i e l migrations indicate that adjacent environments contribute the majority of the food resource base. The association i s more constant for smaller size class f i s h and the dimunition of i t with increasing size i n f e r s that the smaller f i s h are more dependent on the kelp bed than larger 91 ones. The d i s t r i b u t i o n of the adults of the species and the increasing c l i n e i n the sizes of f i s h observed in Barkley Sound, lead me to believe that the v u l n e r a b i l i t y of the young to predation r e s u l t s in a dependence of the species on kelp beds, and probably other s u b - l i t t c r a l refugia, for the i n i t i a l s u r v i v a l of the yearly recruitment to the population. The appearance of recently transformed juveniles in the early stages of the yearly sporophyte growth i l l u s t r a t e s both the coordination of spawning with kelp bed development and the provision to the f i s h of some advantageous feature about the kelp bed. Experimental r e s u l t s show that the juvenile f i s h w i l l respond to the provision of physical shelter i n a manner s i m i l a r to t h e i r response to natural kelp beds. The r e s u l t s lead tc the conclusion that the shelter of the kelp bed i s of primary importance to the juvenile Sebastes melanojjs. 92 5. CONCLUSIONS (i) The l i f e history of Sebastes melanops encompasses a change i n habitat association with the size and age of the f i s h . Adults are associated with the coastal zone while the juveniles associate with inshore features, p a r t i c u l a r l y kelp beds. Young are spawned i n l a t e January - early February and appear i n the kelp beds i n mid - May. Juveniles spend up to four years i n these inshore areas. An increasing c l i n e in the size of f i s h from the inshore to the coastal zone i s present i n Barkley Sound. ( i i ) Higher abundances of juvenile S. melanops are found i n JSS££2£istis -jntegrif o l i a beds than i n beds of the more cumatophytic Nereocjstis luetkeana. In addition, the abundance of juveniles i n Microcystis beds i s inversely correlated with the degree of hydrodynamic exposure of the bed. ( i i i ) In the kelp bed studied, three, or occasionally four, age classes of juveniles are found in the beds, none of which are sexually mature. The absolute abundances of I I , III and IV age-class f i s h are, generally, consistent over time. Fish recruited to a kelp bed often overwinter in the same area during the absence of kelp. (iv) Smaller-sized juveniles (30 - 100 mm) are more intimately associated with the kelp bed than either of the other two size classes. The l a t t e r f i s h occasionally make d i e l feeding migrations from the kelp bed, returning to the bed before n i g h t f a l l . These migrations are thought to be a response to the greater feeding competition r e s u l t i n g from higher densities of population r e c r u i t s i n some years. 93 (v) The kelp bed represents neither a feeding nor a reproductive sanctuary for the f i s h . Adjacent environments supply the primary food resource base. Fish may be ".resident* around a p a r t i c u l a r kelp bed during t h e i r inshore phase, but experiments indicate no f i d e l i t y to that bed should displacement occur. D i s t r i b u t i o n a l pattern of f i s h around the kelp bed has both b i o t i c and a b i o t i c correlates. Abundance of f i s h i s both q u a l i t a t i v e l y and quantitatively correlated with kelp abundance. Fish adopt an alternate habitat durinq periods of kelp absence. At some s i z e , in excess of 200 mm, inshore forms undergo a gradual migration to the coastal zone. (vi) The kelp bed presents several ec o l o g i c a l benefits to the f i s h , the main one of these being the physical shelter of the plants and t h e i r occlusion of the water column. The provision and manipulation of a r t i f i c i a l seaweed shelter induces a numerical response in the f i s h population, s i m i l a r to i t s response to the shelter provided by the kelp plants. (vii) The kelp bed represents an important physical refugium to the f i s h . I t s primary value i s i n the enhancement of the s u r v i v a l of the C - I age class juveniles. 94 6. LITEEATORE CITED Ah 1st ro I D , E. H. 1965. Kinds and abundances of fi s h e s i n the C a l i f o r n i a current region based on egg and l a r v a l surveys. C a l i f . Coop. Ocean. Fish. Invest. 10:31-52. Allen,K.Eadway. 1941. Studies on the biology of the l i f e stages of the salmon (Salmo s a l a r ) . J. 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C i r c . 203. 61 pp. Hobson,E.S. 1973. Diel feeding migrations i n t r o p i c a l reef f i s h e s . Helgolander wiss. Meeresunters. 24:361-370. Holling,C.S. 1959. The components of predation as revealed by a study of small mammal predation on the European pine sawfly. Can. Ent. 91:293-320. Hourston,A.S. 1958. Population studies on juvenile herring in Barkley Sound,B.C. J. Fish. Res. Bd. Can. 15 (5):909- 960. 99 1959. Effects of some aspects of environment on the d i s t r i b u t i o n of juvenile herring i n Barkley Sound,B.C. J. Fish. Res. Bd. Can. 16 (3) : 283-308. Hubbs,Carl L. and L.P.Schultz. 1933. Description of two new American species referable t c the rockfish genus Sebastodes, with notes on related species. Univ. wash. Publ. B i o l . 2 (2): 15-44. Hunter,John R. and C.T.Mitchell. 1668. F i e l d experiments on the attraction of pelagic fishes to f l o a t i n g objects. J. Cons. perm. i n t . Explor. Mer. 31(3):427-434. Hynes,H.B.N. 1950. 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Tech. Rpt. 175. 47 pp. Limbaugh,Conrad. 1955. Fish l i f e i n the kelp beds and the e f f e c t of kelp harvesting. University of C a l i f o r n i a I n s t i t u t e of Marine Resources IMR Ref. 55-9. 158 pp. 1961. L i f e history and ecological notes on the black croaker. Cal. Fish and Game 47 (2): 163-174. 1962. L i f e history and ecol o g i c a l notes on the tnbenose, Aulorhynchus f l a y i d u s , a hemibranch f i s h of western North America. Copeia 1962(3):549-555. MacArthur,R.H. and J.W.MacArthur. 1961. On bird species d i v e r s i t y . Ecology 42 (3):594-598. Martin,N.D. 1960. An analysis of b i r d populations i n r e l a t i o n to forest successsion in Algonguin P r o v i n c i a l Park,Ontario. Ecology 41(1):126-140. 101 Miller,D.J. and R.N.Lea. 1972. Guide to the coastal marine fishes of C a l i f o r n i a . C a l i f . Dept. Fish and Game. Fish B u l l . 157:1-235. Murdoch,William W. 1969. Switching in general predators: experiments on predator s p e c i f i c i t y and s t a b i l i t y of prey populations. Ecol. Mono. 39:335-354. Niska,Edwin. 1973. MS. Species composition of rockfishes i n the catches by Oregon trawlers 1963-1971. Appendix Tables 1-27. Prepared for the 14th Ann. Meeting of Int. Groundfish Conf. Fish. Comm. of Oregon. 35 pp. North,W.J. 1972. (ed.) The Biology of Giant Kelp Beds (!• i n t e g r i f o l i a ) in C a l i f o r n i a . J Kramer. Lehre,Germany 1971. 600 pp. 0'Connell,C.P. 1953. L i f e history of the cabezon. C a l i f . Dept. Fish and Game. Fish B u l l . 93:1-76, Ogawa,Y. 1966. Experiments on the attractiveness of a r t i f i c i a l reefs for marine f i s h e s . Iv . Attraction of stone bream and rudder f i s h to black objects on a white background. B u l l . Tokai Reg. Fish. Res. Lab. 45:137- 145. (English summary) . 1967. Experiments on the attractiveness of a r t i f i c i a l reefs for marine f i s h e s . VII. 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Pavlov,D.S., Yu.N.Sbikin, A.Ye.Vaschinnikov and A.D.Mochek. 1972. The e f f e c t of l i g h t intensity and temperature on the current v e l o c i t i e s c r i t i c a l to f i s h . Voprosy I k h t i o l o g i i 12(4):703-711. P h i l l i p s , J . R . 1957. A review of the rockfishes of C a l i f o r n i a 103 ( f a m i l y S c o r p a e n i d a e ) . C a l i f . Dept. F i s h and Game.Fish B u l l . 104:1-158. P i a n k a , E. B. 1974. E v o l u t i o n a r y . EcojLoajr. H a r p e r and Bow. N .Y. 356 pp. Q u a s t , J . C . 1968a. Some p h y s i c a l a s p e c t s o f t h e i n s h o r e e n v i r o n m e n t , p a r t i c u l a r l y a s i t a f f e c t s k e l p bed f i s h e s . I n : U t i l i z a t i o n o f k e l p bed r e s o u r c e s i n s o u t h e r n C a l i f o r n i a . C a l i f . Dept. F i s h and Game. F i s h E u l l . 139:25-34. 1968b. F i s h f a u n a o f t h e r o c k y i n s h o r e z o n e . C a l i f . D e p t . F i s h and Game. 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B i o l . 46. 38 pp. Tinbergen,Leo. 1960. The natural control of insects i n pine woods, i . Factors influencing i n t e n s i t y of predation by songbirds. Arch, neerl. Zool. 13:225-243. Turner,Charles H. and E.E.Ebert. 1962. The nesting of Chromis punctiEinnis (Cooper) and a description of th e i r eggs and larvae. Cal. Fish and Game 48 (4):243-248. Turner, CH., E.E.Ebert and R. R. Given. 1969. Man-made reef ecology. C a l i f . Dept. Fish and Game. Fish B u l l . 146. 221 pp. Baldron,K.D. 1972. Fish larvae c o l l e c t e d from the northeastern P a c i f i c Ocean and Puget Sound during A p r i l and May,1967. Nat. Ocean. Atmos. Admin., Nat. Mar. Fish. Serv., Spec. S c i . Rpt. Fish. 663:1-16. Hales,J.H. 1952. L i f e history of the blue rockfish, Sebastes l i s t i n u s . C a l i f . Dept. Fish and Game. Fish B u l l . 37:1- 22. 106 Westrheim,S.J., W.S. Hailing and D.Davenport. 1968. MS. Preliminary report on maturity, spawning season and l a r v a l i d e n t i f i c a t i o n of Rockfish (Sebastodes) collected o f f B r i t i s h Columbia i n 1967, Fish. Res. Bd. Can. Manuscript Report 9519 23 pp. Williams,George C. and Doris C.Williams. 1955. Observations on the feeding of the opaleye, G i r e l l a nig.rica.ns. C a l i f o r n i a Fish and Game 41 (3):203-208. Wood,Langley. 1968. Physiological and ecological aspects of prey selection by the marine gastropod Urosalpinx cinerea, (Prosobranchia: Muricidae). Malacologia 6(3):267-320. 107 i££§ndix I F u l l n e s s o f i t o p o d s a n a p i n pcx^S. C r a b s t . r u 4 ) a 4 C a n r e m a i n ^ ] rl '^Vi ( . C ^ r > £ - i for i~ ? is V> ( U r\ i r.{ i ? i cc*.) M o r e s «̂cA C o m m e n Diet a n a l y s i s sunaary sheet 1 A p p e n d i x II 108 Example of an observat ional record Experimental aquarium

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