Length-Weight Relations of Pacific Ocean Perch (Sebastesalutus) in the North Pacific Ocean

S. J. WnsrnnBnr

Department of the EnvironmentFisheries and Marine Service

Pacific Biological Station, Nanaimo, B.C.

lND V. A. SNvrrol

Wrsrnurru, S. J., ^a.No V. A. SNyrro. 1974. Length-weight relations of Pacific oceanperch (Sebastes alutus) in the North Pacific Ocean. J. Fish. Res. Board Can.31: 363-366.

Length-weight relations for Pacific ocean perctr(Sebastes alutus)were determined by theiterative method from data collected aboard Soviet research vessels in the North PacificOcean, from Kamchatka, USSR (53'N lat), to Oregon, USA (44"N lat). Interarea valuesof a (in W : al-o) ranged from 0.0076028 (females, E Bering Sea) to 0.054000 (females,W Bering Sea); and 6, from 2.6345 (females, W Bering Sea) to 3.1694 (females, E BeringSea). Empirical tests indicated that individual area formulae generally produced acceptablecalculated weights. Interarea comparisons of calculated weights provided additionalevidence of the existence of discrete stocks and two subspecies of Paciflc ocean perch in theNorth Pacific Ocean.

Wrsrnnnrlr, S. J., .a.r.ro V. A. SNvrrco. 1974. Length-weight relations of Pacific oceanperch (Sebastes alutus) in the North Pacific Ocean. J. Fish. Res, Board Can.3l: 363-366.

Nous avons 6tab1i des relations longueur-poids de perches de mer du Pacifique (Sebastesalutus) par la m6thode it6rative, d partir de donn6es recueillies d bord des navires de recher-ches sovi6tiques dans le Pacifique Nord, depuis le Kamchatka, URSS (53' lat N), jusqu'dI'Or6gon, E.U. (44'lat N). Les valeurs de a (dans W:al-o), d'une r6gion d I'autre, s'6talentde 0.0076028 (femelles, mer de B6ring E) A 0.054000 (femelles, mer de B6ring O); cellesde 6, de 2.6345 (femelles, mer de Bdring O) d 3.1694 (femelles, mer de Bering E). Des testsempiriques d6montrent que les formules appliqu6es i des r6gions individuelles donnentdes poids calcul6s g6n6ralement acceptables. Les comparaisons interr6gionales des poidscalcul6s fournissent une preuve de plus de l'existence de stocks discontinus et de deuxsous-espdces de S. alutus dans le Pacifique Nord.

363

Received August 21, 1.973

DunrNc the first two Canada-USSR ScientificMeetings on Fisheries, in I97l and 1972, scientificdata dealing with fish stocks of mutual interestwere exchanged. Among these data were length-weight measurements of Pacific ocean perch (,Se-bastes alutus) caught by Soviet research vessels inthe North Pacific Ocean.

These data were compiled, processed, and com-pared with similar data published elsewhere.

Materials and methods -A11 f,sh were caught bytrawl, Length, sex, and weight data were collected

lPresent address: Pacific Scientific Research Instituteof Fisheries and Oceanography, Vladivostok, USSR.

Printed in Canada (13149)

Accepted November 29, 1973

at sea. Each fish was measured to the nearest 0.1 cm,fork length, and weighed to the nearest l0 g. Mostsamples were random, and consisted of 50 or 100 fish.

Sarnples were grouped arbitrarily into the followingnine areas, which generally conform with subdivisionssuggested by Barsukov (1964) andlor Westrheim(1970).

Area Approximate extent

W Bering Sea (west of 180" long) 53-62"NE Bering Sea (east of 172"W) 61"NAleutian IslandsUnimakKodiakYakutatSE AlaskaBritish ColumbiaWashington-Oregon

165 E-l70'W166-164"W153-148'Wt47-137"W56'14',-54'34',N51'38',-48'49',N4'1"55',-44"44',N

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364 JoURNAL FISHERIES RESEARcH BoARD oF cANADA, voI,. 31, No. 3, 1974

Tasr,E 1, Length-weight coefficients& for Pacific ocean perch (Sebastes alutus) by area, 1.966-71.

Males Females

AIea Y e a r N b a b N b a b

W Bering 1966;1,969-71 580 0.029923 2.7762 592 0.054000 2.6345(2s,46) (27-46)

E Bering 1970-71 545 0.025601 2.8088 371 0'0076028 3.1694(22-44) (20-47)

Aleutian 1966:1969-71 '16'7 0.041569 2.6621 69s 0.044816 2.6511(1e-42) (19-46)

Unimak 1968:19'10-71 320 0.016641 2.9290 22O 0.022552 2.8409(20-40) (21-39)

Kod iak 1971. 153 0 .014168 2 .9881 144 0 .012263 3 .0303(23-40) (22-44)

Yakutat 1971 204 0.015672 2.9692 146 0.012265 3.0376(24-40) (26-41)

SE Alaska 19'71 178 0.020336 2.8854 217 0.018239 2.9240(22-40) (22-42)

British Columbia 1968-70 828 0 .019215 2.9061 600 0 .011529 3 .0573(17-4s) (19-47)

Washington-Oregon 1968-71 656 0. 038384 2 .'7411 682 0 .019495 2 .9337(18-45) (24-46)

Total 4231 3667

"For the formula W : al-b, where W : weight in grams, and L : fork length in centimeters.bN : numbers sampled. Size range (cn) in parentheses.

T.q.sr,r 2. Length-weight coefficients, sexes combined, and calculated weights (g) at selected lengths for Paciflcocean perch, by area.

Coefficients" Calculated weight (g) at

Source a b 25 cm 35 cm 45cm

W Bering Sea This study 0.025566 2.8305 232 600 1222E Bering Sea 0.007950 3.1441 198 569 1254Aleutian Islands 0.0379'77 2.6929 221 546 1075Unimak 0.018286 2.9O2O 208 553 1147Shumagin Islands Westrheim (1967) 0.032038 2.72733 208 521 1,034Kodiak This study 0.013101 3.0109 212 584 1244

ch ikun i 4971) 0 .015439 2 .s485 204 551 1156

Yakutat This study 0.014052 2.9997 219 602 1,279SE Alaska This study 0.016882 2.9429 219 591 1238

Westrheim (1971) 0.014023 2.98899 211 578 1225

Brit ish Columbia This study 0.010909 3.0660 211 591 1278Westrheim and Thomson

(1971) 0.0088955 3.13325 213 613 1346

Washington-Oregon This study 0.023938 2.8746 250 657 1353Westrheim (1958) 0.010313 3.08686 213 602 1308

"For the formula W : al-b, where W : weight in grams and L : fork length in centimeters.J. F

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All data were compiled, and processed by computer,at the Paciflc Biological Station. For comparativepurposes, processing procedures followed those ofWestrheim and Thomson (1971). Regression para-meters were obtained by the iterative method ratherthan the conventional log-1og method.

Results- Measurements of 4231 male and 3667female ocean perch were used in this analysis(Table 1). Most of the data were collected duringthe third and fourth quarters of the year - onlythe British Columbia area was sampled in all fourquarters. Values of a, in the formula W : al-b,for males ranged from 0.014168 (Kodiak) to0.041569 (Aleutian Islands), and for females,0.0076028 (E Bering Sea) to 0.054000 (W BeringSea). Values of 6 for males ranged from 2.6621(Aleutian Islands) to 2.9881 (Kodiak), and forfemales, 2.6345 (W Bering) to 3.1694 (E BeringSea).

Unimak, Kodiak, and Yakutat formulae weretested empirically with length-frequency samplesofknown weight collected from each of these areasby the Canadian research vessel G. B. Reed during1963-65. The results, listed below, indicate anoverall accuracy of -6.7 to 15.87o. Only theYakutat formula appears to have a bias, which ispositive.

/e deviationNo. of

Area samples

Unimak 5Kodiak 8Yakutat 6

Kodiak, SE Alaska, British Columbia, andWashington-Oregon formulae were tested by com-paring calculated weights, at selected lengths, withthose of other formulae from the same area (Table2). The results, listed below, indicate good agree-ment except for the Washington-Oregon formula.

/6 deviatiot at:

Area 25 cm 35 cm 45cm

+ 6 . 0 + 7 . 6+ 2 . 2 + 1 . 1- 3 . 6 - 5 . 1

+ 1 0 . 0 + 3 . 8

The Kcdiak formula produced calculated weightsconsistently larger (3 .9-:1 .6%) than those fromChikuni's (1971) formula. The SE Alaska andBritish Columbia formulae produced calculatedweights quite similar (-5.1 to +3.8%) to those ofWestrheim (1971) and Westrheim and Thomson

Kodiak +3.9SE A laska +3.8British Columbia -0.9Washington-Oregon +18.8

365

(1971), respectively, whose accuracy had beenestablished, empirically, to be about J-5%.

-the

Washington-Oregon formula produced substantiallylarger (3.8-18.87d calculated weights than thatof Westrheim (1958), and is suspect since the latterformula produced satisfactory estimates in a catch-sampling study (Westrheim 1967). All of thesecomparisons would likely yield statistically signif-icant differences. Westrheim and Thomson (1971)found statistical differences (using covariance anal-ysis), by sex, area, and season, for deviations of2-8/o. However, as the absolute accuracy of catchweights or landed weights is probably no betterthan 5-10/e, the conventional statistical tests seeminappropriate.

Among areas, calculated weights at selectedlengths were generally maximal at the extreme endsof the study region - Bering Sea and Washington-Oregon (Fig. 1 and Table 2). These interarea dif-ferences were most pronounced for 45-cm fishand least so for 25-cm fish. Notably, the BeringSea fish were appreciably heavier per selected lengththan those in adjacent areas to the south and east.For example, calculated weights of 45-cm fish wereL222 gin the W Bering arca, 1254 g in the E Beringarea, and 1075-1147 g in the Aleutian-Unimakregion.

S E R I N G S E A N , E . P A C I F I C

S E S T E A S T A I U U S H K O Y A S E A C W O

A P4 5 c m . / L

.2-'--*I

A

A

O T h l s 3 t u d yA o i h e r s t u d i e s

o---_o

2 5 c m

*-+-r-+---o---*-o-4

Frc. 1. Calculated weights, by area, of 45-, 35-,and 25-cm Pacific ocean perch (Sebastes alutus).Areas: AI : Aleutian Islandst UU : Unalaska-Unimak; SH : Shumagin; KO : Kodiak; Yd :Yakutat; SE : SE Alaska; BC : British Columbia;WO : Washington-Oregon,

Range Mean

-2 .0 t o 4 -2 .5- 6 . 7 t o * 5 . 8+ 2 . 4 t o + 5 . 6

J-o ?

+ 1 . 7+ 4 . 2

4 0 0

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366 JOURNAL FISHERIES RESEARCH BOARD OF CANADA, VOL. 31, NO. 3, 1974

Discussion - Interarea comparisons of the length-weight relations provided additional evidence ofdiscrete stocks of Pacific ocean perch in the NorthPaciflc Ocean. Calculated weight, by selected length,increased eastward and southward from the AleutianIslands area to the Washington-Oregon area. Theseweight differentials suggest there ate discretestocks of Pacific ocean perch along the coast ofNorth America. Other workers have deduced thesame situation based on catch records (Fadeev1968), size composition and dominant year-classes(Westrheim 1970), length-weight and length-girth(Westrheim 1971), fecundity, spawning season,age at maturity, mean length, and mean weight(Snytko 197Ia, b), and growth (Westrheim 1973).

Interregional comparisons suggest that the BeringSea specimens are different from those in adjacentAleutian and Unimak areas. Calculated weights,at selected lengths, in the Bering Sea region aregenerally greater. This phenomenon seems to reflectthe difference between the two subspecies of Pacificocean perch proposed by Barsukov (1964) - Se-bastes alutus paucispinosus (Honshu Island toSoutheast Bering Sea) and ,S. a. alutus (AleutianIslands to California). He noted in his key thatbody depth at the origin of the ventral fins wasgenerally greater for S. a. paucispinosus,

Acknowledgments -We wish to acknowledge withthanks the assistance of those who collected the dataat sea and compiled and processed the data ashore.

Bansurov, V. V. 1964. A key to the fishes of theScorpaenidae family occurring in the trawl catcheson the continental slope of the Bering Sea and theGulf of Alaska. Proceedings of the Pacific ScientificResearch Institute of Marine Fisheries and Ocean-ography (TINRO) 52: 233-266.

CnrcuNr, S. 1971. On the age and size relationshipof the Pacific ocean perch in the northeastern Pacific.8u11. Far Seas Fish. Res. Lab. (Shimizu) 4: 27-49.

Flornv, N. S. 1968. Migrations of Pacific oceanperch. Izv. Tikhookean. Nauchno. Issled. Inst.Rybn. Khoz. Okeanogr. 65: 1,70-177. (Transl.from Russian by Fish, Res. Board Can. Transl.Ser. No. 1447, 1970)

SNvrro, V. A. 1971a. Pacific ocean perch (Sebas-todes alutus G.) of the Vancouver-Oregon region(commercial-biological characteristics). Proceedingsof the Pacific Scientific Research Institute of MarineFisheries and Oceanography (TINRO) 75: 56-65.(Transl. from Russian by Fish. Res. Board Can,Transl. Ser. No. 2431, 1973)

1971b. Biology and peculiarities of Sebastodesalutus G. distribution in Vancouver-Oregon region.Proceedings of the Paciflc Scientific Research Insti-tute of Marine Fishories and Oceanography (TINRO)79: 3-41, (Transl. from Russian by Fish. Res.Board Can. Transl. Ser. No. 2805, 1973)

Wrsrnurru, S. J. 1958. On the biology of the Pacificocean perch, Sebastodes alutus (Gilbert). M.Sc.Thesis. Univ. Washington, Seattle, Wash. 106 p.

1967. Sampling research trawl catches at sea.J. Fish. Res. Board Can. 24: 1.187-1202.

1970. Survey of rockfishes, especially Pacificocean perch, in the Northeast Pacific Ocean, 1963-66. J. Fish. Res. Board Can. 25: 1781-1809.

1971. Length-weight and length-girth relation-ships for Pacific ocean perch (Sebastes alutus) col-lected off Southeastern Alaska in August 1971.Fish. Res. Board Can. Tech. Rep. 281: 10 p.

1.973. Age determination and growth of Pacificocean perch (Sebastes alutus) in the NortheastPacific Ocean. J. Fish. Res. Board Can. 3O; 235-1 / 1

WrsrnuEru, S. J., aNoJ. A. TnousoN, 1971. Weight-length relationship fol Pacific ocean perch (Sebastesalutus) coTlected off British Columbia in 1969.Fish. Res. Board Can. Tech. Rep. 237: 12 p.

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