Sexual Dimorphism in Postembryonic Development of Saffron Cod (Eleginus gracilis), Walleye Pollock (Gadus chalcogrammus), and Pacific Cod (Gadus macrocephalus)

Sexual dimorphism and allometric variability between males and females during the postembryonic development of saffron cod, walleye pollock, and Pacific cod were determined for the first time based on Hexley’s allometric equation, Brody’s model of body weight, and using factor and cluster analyses for a set of morphometric parameters. Sexual dimorphism in eye diameter, maximum body depth, antedorsal and anteanal distances is manifested as early as in the juvenile stage. In almost all of the studied size–age groups, females of saffron cod and walleye pollock surpass males in terms of head size, interorbital space, antedorsal distance, eye diameter, and body depth. The increment of morphological features in these fishes alternates between isometry and positive or negative allometry. No sexual dimorphism is observed in Pacific cod. The increment of all studied morphological features is linear, except for the increase in body weight relative to length. According to the factor analysis, standard length, maximum body depth, eye diameter, and interorbital space contribute the most to the total variability both within and between age groups of the studied species. Cluster analysis revealed general trends in the morphophysiological variability of saffron cod and walleye pollock.