QUAST: MORPHOMETRIC VARIATION ON PACIFIC OCEAN PERCH 



Table 1. — Standard-length (SL) frequencies of Pacific ocean perch used in this study. Geo- 

 graphic zones are shown in Figure 1 . M = male; F = female. 



'Class midpoints weighted by frequency. 



of the fish. 

 Longest pectoral -fin ray.— From tip of the longest 



ray to its origin. 

 Upper-jaw length. — Greatest distance from tip of 



the premaxillary to posterior edge of the maxil- 

 lary. 

 Upper-jaw width. — Greatest width of this part 



taken perpendicular to axis of the mouth line in 



a closed mouth. 

 Symphyseal knob. — From tip of symphyseal knob 



to its posterior insertion. 

 6th dorsal spinous fin ray. — From tip of this fin 



ray to its posterior insertion. 

 13th spinous ray in dorsal fin. — From tip of this 



ray to its posterior insertion. 

 3d anal-fin spine. — From tip of this spine to its 



posterior insertion. 



The data were divided into six geographic re- 

 gions (Atka-Bering, Atka-Gulf, Kodiak, Yakutat, 

 Southeastern, and Vancouver (Fig. 1)), and mea- 

 surements regressed on SL by sex after all vari- 

 ates were logio transformed. (Transformation al- 

 lowed measurements to be expressed as linear 

 functions of SL and stabilized the variance.) Geo- 

 graphic and sexual variation were tested by anal- 

 ysis of covariance (ANCOVA), with statistical 

 tests "significant" when P < 0.05. 



In "allometric" growth in fishes, the size of one 

 variate bears a power relationship to an index of 



body length. The power exponent can be ex- 

 pressed as the slope of a simple linear regression 

 fit to log-transformed variates, the "allometric 

 equation", as used in this study. A slope greater 

 than unity, "positive allometry" (Simpson et al. 

 1960), indicates that growth in a body dimension 

 relative to growth in fish length (SL in the 

 present paper) increases as fish length increases; 

 a slope less than unity, "negative allometry", in- 

 dicates that growth in a body dimension de- 

 creases; and a slope of unity, "isometry", indicates 

 that it stays the same. 



A preliminary survey of the measurement data 

 disclosed that most body dimensions probably 

 grow allometrically, although not strongly so be- 

 cause slopes are near unity (Table 2). Because 

 body proportions that relate size of a character to 

 SL are specific to body length when growth is 

 allometric, both proportions and dimensions must 

 be referred to a size standard if either are to be 

 objectively compared. For this reason, measure- 

 ments and proportions used here are usually re- 

 ferred to a hypothetical fish of 260 mm SL, a size 

 near the average for all specimens in the study 

 (Table 1), and likely a common collection size. In 

 most instances, body proportions represented by 

 estimated dimensions at the standard size need 

 not be limited to exactly that size for purposes of 

 general comparison because of the proximity of 

 allometric slopes to unity (Table 2). The data 



665 



