EVIDENCE FOR DISTINCT STOCKS OF KING MACKEREL, SCOMBEROMORUS-CAVALLA,IN THE GULF-OF-MEXICO

Evidence supporting a two stock hypothesis for king mackerel, Scombero morus cavalla, in the Gulf of Mexico was developed principally from th e results of electrophoretic patterns of one polymorphic dipeptidase l ocus and supporting evidence from mark-recapture, charterboat catch, a nd spawning studies. There are two identifiable stocks of king mackere l in the Gulf of Mexico: a western stock and an eastern stock. The wes tern stock migrates northward along the Mexico-Texas coast during the spring and early summer from its winter grounds in Mexico (Yucatan Pen insula). This stock has a high frequency of the dipeptidase PEPA-2a a llele. The eastern stock migrates at the same time northward along the eastern coast of the Gulf of Mexico from its winter grounds in south Florida (Gulf of Mexico and Atlantic coast). This stock has a high fre quency of the dipeptidase PEPA-2b allele. Both stocks migrate simulta neously into the northern Gulf of Mexico and mix at varying degrees in the northern summering grounds (Texas to northwest Florida).