MORPHOMETRIC VARIATION OF PACIFIC OCEAN PERCH, 

 SEBASTES ALUTUS, OFF WESTERN NORTH AMERICA 



Jay C. Quast' 



ABSTRACT 



Pacific ocean perch, Sebastes alutus, vary in body form over the eastern Pacific Ocean and southeast- 

 ern Bering Sea. When related to a 260 mm standard length, a small adult size, most of 18 body 

 measurements change from east to west as V-shaped clines. Belly size, however, lengthens as a single 

 cline from the Vancouver vicinity westward, and the lengthening is coupled with shortening of 

 measurements complementary to the belly measurement, from head to belly and belly to tail. Most 

 adult body dimensions are sexually dimorphic, but the dimorphism is slight. Growth inflections may 

 occur but, if so, are hidden in the data. Body form does not change markedly with growth except for 

 the symphyseal knob, which becomes relatively larger, and the 3d anal-fin spine, which becomes 

 relatively shorter. Putative subspecies of S. alutus probably are premature because supportive mor- 

 phometric comparisons and criteria on the subspecies seem based on too few data, and do not ade- 

 quately consider complex clinal variation and growth allometry evidenced in the eastern part of the 

 species range. Also, significant morphometric variation may be phenotypic. 



Pacific ocean perch, Sebastes alutus, a commer- 

 cially important rockfish (Scorpaenidae) in the 

 North Pacific Ocean, range ft-om northern Hon- 

 shu, Japan, to California. To date, the species' 

 taxonomy has been based on relatively limited 

 local representation, on preserved material, and 

 on analyses without probabilistic interpretation 

 or attention to allometric growth. Matsubara 

 (1943) identified a Honshu representative as a 

 new species {Sebastes paucispinosus), but Bar- 

 sukov (1964), after examining specimens taken 

 across the North Pacific Ocean, suggested that 

 the variation he found indicated, at most, possible 

 eastern and western Pacific subspecies, with both 

 possibly occurring off the Aleutian Arc. Chen 

 (1971) demonstrated that growth rate, can influ- 

 ence body proportions in a Sebastes species, and 

 Westrheim (1973) found a cline of increasing 

 growth rate in S. alutus from the northern Gulf of 

 Alaska to Washington (Quast^ found that the 

 cline may be more related to latitude than tem- 

 perature). 



Because of the commercial importance of 

 Pacific ocean perch and the lack of definitive in- 

 formation on possible subspecies or genetic stocks 

 at the onset of the study, the National Marine 



'Northwest and Alaska Fisheries Center Auke Bay Labora- 

 tory, National Marine Fisheries Service, NOAA, P.O. Box 

 210155, Auke Bay, AK 99821; present address: 1565 

 Jamestown Street S.E., Salem. OR 97302. 



2Jay C. Quast. Annual growth in Pacific ocean perch, Se- 

 bastes alutus: variation, stanzas, compensation, and simula- 

 tion. Manuscr. in prep. 



Manuscript accepted June 1987. 



FISHERY BULLETIN: VOL. 85, NO. 4, 1987. 



Fisheries Service gathered morphometric data on 

 representatives from the Gulf of Alaska and east- 

 ern Bering Sea from 1968 to the mid-1970's. We 

 sought evidence of disjunct geographic variation 

 that might indicate genetic stocks, and analyzed 

 for characteristics of growth and sexual variation 

 of possible taxonomic significance. Sampling was 

 in the shallow range of the species distribution, at 

 <200 fathoms (366 m). 



METHODS 



The prohibitively large volume needed for spec- 

 imen storage for an extensive statistical study 

 and the shrinkage, bending, and other distortions 

 caused by preservation were avoided by pho- 

 tographing freshly trawled Pacific ocean perch. A 

 portable stand supported a 35 mm camera and 

 flash unit 145 cm above a V-shaped easel, which 

 helped restrain the fish from vessel motion. The 

 long focal distance minimized foreshortening in 

 the photographs, and a 100 mm telephoto lens 

 reduced field size to include only the specimen, a 

 centimeter scale, a numbered theater ticket, and 

 a plastic card with pencil-inscribed catch infor- 

 mation. Specimens were flattened, straightened, 

 and centered on the easel; fins were placed as 

 erect as possible; and the lower jaw was propped 

 closed with handheld forceps. Later, in the labo- 

 ratory, body measurements were taken from im- 

 ages projected from the color transparencies onto 

 the back of a ground-glass screen. The images 



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