QUAST: MORPHOMETRIC VARIATION ON PACIFIC OCEAN PERCH 



dimensions had the lowest unassigned variabiHty 

 when corrected for size. 



As would be expected from the plots of charac- 

 ter measurements (Fig. 2), sexual and geographic 

 variation were important components after the 

 size effects were removed (Table 4). For sexual 

 variation, the hind-trunk dorsal, spinous-dorsal 

 fin, and body-depth pelvic measurements were 

 the poorest discriminators, and belly, hind-trunk 

 ventral, and longest pectoral-fin ray the best. For 

 geographic variation, 3d anal-fin spine, symphy- 

 seal knob, and 6th spinous ray in dorsal fin were 

 the poorest discriminators, and belly, hind-trunk 

 ventral, and head measurements the best. 



Present Nominal Subspecies 

 are Questionable 



Barsukov (1964) synonymized the nominal spe- 

 cies Sebastodes alutus (Gilbert) and S. pau- 

 cispinosus (Matsubara) but suggested that the 

 eastern and western Pacific representatives may 

 be separate subspecies: S. a. paucispinosus 

 ranging from Honshu to Olyutorskii Bay and 



along the northern Bering Sea slope, perhaps to 

 Bristol Bay; and S. a. alutus ranging from Cali- 

 fornia to the Gulf of Alaska and along the Aleu- 

 tian Arc to, and including, the Commander Is- 

 lands. Barsukov morphologically distinguished 

 the subspecies by "Alaskan Seb. alutus longer 

 than 23 cm are quite noticeably distinguished 

 from Seb. alutus from other parts of the range by 

 body depth", and in a key gives the principal sub- 

 species discriminator as whether the ratio SL/ 

 body depth of 170-360 mm SL fish is greater than 

 3.2 iS. a. alutus) or less (S. a. paucispinosus). 



The question of eastern and western subspecies 

 in S. alutus seems more complex than Barsukov 

 (1964) suggested. The weight of present evidence, 

 although preliminary, does not seem to justify the 

 nominal subspecies. First, there is the problem of 

 how populations sympatric over a distance as 

 great as the Aleutian Arc could maintain repro- 

 ductive isolation adequate to insure genetic dis- 

 tinctiveness. There is no evidence for isolating 

 mechanisms in the species — on the contrary, the 

 larvae are pelagic (Hart 1973), which should pro- 

 mote rapid genetic exchange over major distances 



Table 4. — Relative degree that measurements in standard-sized Pacific ocean perch of 260 mm SL reveal geographic 

 and sexual variation. In the variation sections, variation not related to character size was indexed by alternate 

 coefficients of variation that were pooled over all samples, sexual variation was indexed by differences between sexes 

 as a percentage of their mid-size in each region (positive if males averaged larger than females and negative if males 

 were smaller, but only absolute values were used in calculations), and geographic variation was indexed by the 

 maximum difference between regions as a percentage of mean-estimate size of measurements from the Kodiak region 

 (Table 3). In the discnmination section, indices indicate relative magnitudes of sexual and geographic variation relative 

 to variation not related to character size. Low values or ranks (in parentheses) indicate that variation not related to 

 character size was high relative to sexual (data column 4) or geographic (data column 5) variation; hence, the 

 measurement is a poor indicator of sexual or geographic variation, and vice versa. Kendall Coefficient of Concordance 

 (Siegel 1956) between ranks for sexual and geographic vanation was not significant. 



677 



