Serum Esterase Groups of Pacific and Atlantic Tunas

Starch-gel electrophoretic analysis of serum specimens of 8201 skipjack tuna (Katsuwonus pelamis), 187 albacore (Thunnus alalunga), 107 bigeye tuna (T. obesus), and 65 yellowfin tuna (T. albacares) taken from the Pacific and Atlantic oceans demonstrated individual genetic variations in the serum esterase component within each species. The esterase system proved to be independent of any known blood group systems, of sex, and of size of fish in each species. In skipjack tuna extensive data allowed an application of the system to the problem of identifying subpopulations, or isolated breeding populations. Heterogeneity tests for the gene frequencies of the esterase system showed: a) a population in the equatorial Atlantic is different from any populations recognized in the Pacific; b) eastern Pacific (Baja California) specimens were indistinguishable from those of Hawaiian waters; and c) the western Pacific (Japan and Palau) has at least one subpopulation different from the population in Hawaiian waters.