w i~h ou f 01j;<;rr. in?icaticllll of their rnm:u~cript 'status. OF. CANADA FISH ERIES ANa MARINE SERVICE No DavidW. Narver

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1 ... This series ~ndades, llh'wj,ublish~ ' prehn1;incrry feports and dater r. tords not i'ftencled igr general.distriibubon. 'They shoilld not b~ tefe'n:e i to in ldu'li>licatioms lith gut d e.cx'cmce from the issuing BoaFd estahllishl!r nt rm d w i~h ou f 01j;<;rr. in?icaticllll of their rnm:u~cript 'status. FSH~~_S '., ~ESEABC~ ~»OABn -'EN V.RONME:N1' CANADA OF. CANADA FSH ERES ANa MARNE SERVCE -BOLOGfCAL $TA. :i. WATER 8T. EAS ST. JOHN'S. NF&.o"CANADA A1CtA1 MANUSCRPT REPO RT SE.RES No Age and. Sizeo-f Rainbow Trout at the Outlet of Babine Lake and in Babine 'River by DavidW. Narver Pacific Bi(;)logical Station, Nanaimo, B.C.

2 This series includes unpublished preliminctty reports and datq records not intended for general distribution. They should not be referred to in publications without Clearance from the issuing Boqrd establishment (md without Clear indication of their manuscript stat\.ls. FSHERES OF RESEARCH CANADA BOARD MANUSCRPT REPORT SERES No Age and Size of Rainbow Trout at the Outlet of Bahille Lake and in Babine River by David W. Narver Pacific Biological Station, Nanaimo, B.C. May 1975

3 NTRODUCT 00 Rainbow trout are the most important sport fish in terms of angling effort in the Babine Lake system. Griffiths (1968) has reported on the age and growth of rainbow in the main part of Babine Lake but little or no information exists for Babine River. The purpose of this paper is to report the age and size composition of rainbow trout caught in the North Arm-Babine River Ni1kitkwa Lake area in n the middle and late 1960's the Pacific Bio1ogic~1 Station (Research and Development Branch, Fisheries and Marine Service) studied the density, distribution and behaviour of juvenile sockeye salmon in the Babine Lake system (Narver 1970; McDonald 1969; Clarke and Smith 1972 ; McCart 1967 ; Smith 1973). n the North Arm-Babine River area rainbow trout are readily observed feeding on sockeye fry and smo1ts. Changes in juvenile sockeye salmon abundance as a result of the development of spawning channels might be passed on to rainbow trout in terms of changes in growth or abundance. Essentially this study sets a predeve10pment baseline for rainbow trout in this part of the Babine system. METHODS We arranged for the two fishing resorts operating in the Babine River-Ni1kitkwa Lake area to collect certain data for us in Envelopes were used for each fish. n each envelope were placed scales taken by a knife scrape within three scale rows of the lateral line and between the dorsal and anal fins. n addition the species, date, location, length, weight and sex was recorded on the outside of the envelope for each fish. Later, each scale sample was placed in a detergent solution and the several largest scales with the best shape and least amount of regeneration were selected. These were mounted on gummed cards (50 fish per card) and impressed into acetate under heat and pressure (Clutter and Whitesel 1956). For age interpretation the scale image was projected onto a white table at about 150X. RESULTS AND DSCUSSOO The program resulted in 183 fish being sampled by the resort operators. These consisted of 171 rainbow trout,ll cutthroat trout and 1 Dolly Varden. Of the samples that had fishing location noted, 69 were Babine Lake (North Arm), 60 were Ni1kitkwa Lake (Smokehouse sland) and 37 were Babine River (above and below Ni1kitkwa). The 11 cutthroats were all caught in Babine River or Ni1kitkwa Lake and consisted of six 9 and five d o They had the following size and age composition:

4 -2- Age n Mean length ~cm} Mean weight {kg} V 1 47, The single Dolly Varden was caught in Babine River and was a male 57.1 cm in length and kg in weight. The age-length data for the 171 rainbow trout with readable scales is summarized in Table 1. Mean length ranged from 28.3 cm for age rainbow trout to 58.7 cm for age V (Fig. 1). The largest rainbow in the samples was 62.6 cm in length, weighed 1.98 kg and was age V. The mean lengths by age of rainbow in this study are much larger than those reported by Griffiths (1968), although most of his samples were from the main Babine Lake. Griffiths' data are backcalculated to each annulus while the present data are actual fish lengths iricluding growth of the year (plus growth). Griffiths Table V V V V V X X , t is not clear whether this large difference is entirely.due to sampling and data treatmerit or also reflects a real growth difference in two parts of the Babine system. Griffiths' backcalculated lengths are probably the best estimates of size. He shows that the backcalculated lengths approximate the mean length from trout catches by purse seine. My data is from middle to late summer sport catches and are probably biased in favour of the larger fish of each age group (at least the youngest groups) plus the growth of the year. t was of interest to separate the Babine Lake (North Arm) fish from those taken in Babine River-Nilkitkwa Lake. Babine Lake fish tended to be slightly longer and older. Overall mean size was 38.3 cm with Babine Lake fish being 41.2 and Babine River-Nilkitkwa being The Babine River fish were composed of 68% age and V while the North Arm consisted of 51% of these two age groups and another 40% were of age V and V (Table 1). The length-weight relationships of these samples were: Babine River-Nilkitkwa wt.= X ln 3. l27 Babine Lake wt. = X ln Combined wt. = X ln3.l467 Analysis of covariance shows that the slopes of the two relationsilips (Babine River-Nilkitkwa and Babine Lake) are not significantly different but that the origins of the slopes are significantly different. Thus for a given

5 -3- length, rainbow trout in Babine Lake are slightly heavier than are those in Babine River-Nilkitkwa (Fig. 2 and 3). The relationship for the combined samples is given in Appendix. Analysis of variance table D.F. MS F B() = "/d( B( l) 's equal A's equal '0'< Residual The rainbow trout scales show a consistent and characteristic pattern: narrow spacing of circuli in the first, second and third (most <commonly second) year followed by more rapid annual growth. This same "anadromous" growth pattern for trout in lakes is apparently common. have seen it in Great Central Lake cutthroat and rainbow in liamna Lake, Alaska. Griffiths (1968) comments on it for rainbow trout in the main Babine Lake. Most likely the fish spend 1 to 3 years in a nursery tributary, where growth is relatively slow, prior to taking up lake residency where food may be more plentiful. LTERATURE CTED Clarke, W.C.; and H.D. Sm i th Observations on the migration of sockeye salmon fry (Oncorhynchus nerka) in the lower Babine River. J. Fish. Res. Board Can o 29: Clutter, R.., and L.E. Whitesel Collection and interpretation of sockeye salmon scales. nt. Pac. Salmon Fish. Comm. Bull. 9: 159 p o Griffiths, J.S gardneri) and the British Columbia. Growth and feeding of the rainbow trout (Salmo lake trout (Salvelinus namaycush) from Babine Lake, Honour Thesis, Zoology, Univ. Victoria. 56 p. McCart, P Observations on the behavior and ecology of sockeye salmon fry in the Babine River. J o Fish. Res. Board Can. 24: McDonald, J.G Distribution, growth and survival of sockeye fry (Oncorhynchus nerka) produced in natural and artificial stream environments. J. Fish. Res o Board Can. 26: Narver, DoW Diel vertical movements and feeding of underyearling sockeye salmon and the limnetic zooplankton in Babine Lake, British Columbia. J. Fish. Res. Board Can. 27 : Smith, H.D Observations on the cestode Eubothrium saluelini in juvenile sockeye salmon (Oncorhynchus nerka) at Babine Lake, British Columbia. J. Fish. Res, Board Can. 30:

6 -4- Table 1. Summary of length by age data for rainbow trout in Bab ine Lake- Bab ine River J Babine River- North Arm Nilkitkwa Lake Weighted mean n 10 x s n 10 - x s n 10 x s V V V V V x

7 70 6 f 50 '"':' E.s 40 z... C!) z W...J 30 t../l T m N V AGE GROUP V Vii VTi Fig. 1. Mean, standard deviations and range of lengths by age group for rainbow trout in lower Babine Lake-Babine River-Nilkitkwa Lake, 1969.

8 C :? 'E SO WEGiT CKGJ - LENrrH COAJ REJ...,A.Tt:JE.HP CF AAre:JW TRO.JT 2 6 N 8.A8r RVER N-V NLKTKWA LME, 1.$9 WT= ui r-"\. LJ ~ 1 4 "--J LJ 0.8 H W ~ , t. "./. 1 0 t J C :? 'E SO LENGTH (em) Fig. 2. Weight-length relationship for rainbow trout in Babine River-Nilkitkwa Lake, 1969.

9 S B ~ 3B WEGiT (KG) - LEN3TH (0.1) REL.AT(N;HP CF AA~ TRClJT,-, ~ ~ J N Bi'Br L.ME, 1969 WT= O. r:xxxx:17703 ur' 0942 ~ ~ 0 8 H W ~ S B "37 3B SO LENGTH (em) Fig. 3. Weight-length relationship for rainbow trout in Babine Lake (North Arm), 1969.

10 S 26 C ) :i ;7 ~ ::E EiO 'E"ErT (KG) - L..EJ.GTH (CW) REl.A Teta up CF RAlt-aJW TRlJT j N 8Nf,.t LME. BABlt RVER N-CJ NLKTKWA LME. WT= o CXXlOO L..J.i Ei9.Y: - /' l= 2 6,-, =1 ~ 1 8 LJ ~ j -? "--' ~ ;./ ~a ~ 3: [ c j ~/ l.. / - -/ ~ C ) :i ;7 ~ ::E EiO LENGTH (em) Appendix. Weight- length relationship for rainbow trout in Babine Lake-Babine River-Ni1kitkwa, 1969.