Abstract. Evidence support- 

 ing a two stock hypothesis for king 

 mackerel, Scomberomorus cavalla, 

 in the Gulf of Mexico was devel- 

 oped principally from the results of 

 electrophoretic patterns of one 

 polymorphic dipeptidase locus and 

 supporting evidence from mark- 

 recapture, charterboat catch, and 

 spawning studies. 



There are two identifiable stocks 

 of king mackerel in the Gulf of 

 Mexico: a western stock and an 

 eastern stock. The western stock 

 migrates northward along the 

 Mexico-Texas coast during the 

 spring and early summer from its 

 winter grounds in Mexico (Yucatan 

 Peninsula). This stock has a high 

 frequency of the dipeptidase 

 PEPA-2*a allele. The eastern stock 

 migrates at the same time north- 

 ward 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 frequency of the 

 dipeptidase PEPA-2*b allele. Both 

 stocks migrate simultaneously into 

 the northern Gulf of Mexico and 

 mix at varying degrees in the 

 northern summering grounds 

 (Texas to northwest Florida). 



Evidence for distinct stocks of 

 king mackerel, 

 Scomberomorus cavalla, 

 in the Gulf of Mexico 



Allyn G. Johnson 



William A. Fable Jr. 



Churchill B. Grimes 



Lee Trent 



Southeast Fisheries Science Center 

 National Marine Fisheries Service. NOAA 

 3500 Delwood Beach Road 

 Panama City. Florida 32408 



Javier Vasconcelos Perez 



Instituto Nacional de la Pesca 

 Mexico City. Mexico 



Manuscript accepted 17 August 1993 

 Fishery Bulletin 92:91-101 (1994) 



The king mackerel, Scomber- 

 omorus cavalla, is a widely distrib- 

 uted, coastal pelagic species in the 

 western Atlantic Ocean. This 

 scombrid is found from the Gulf of 

 Maine to Rio de Janiero, Brazil, in- 

 cluding the Gulf of Mexico and 

 Caribbean Sea (Rivas, 1951; 

 Collette and Nauen, 1983). It is a 

 valuable resource that supports 

 fisheries throughout most of its 

 range (Manooch et al., 1978). 



The U.S. and Mexico have been 

 major exploiters of king mackerel 

 resources. U.S. commercial land- 

 ings have been reported since 1888. 

 Landings have ranged from 2,213 

 metric tons (t) (1972) to 4,746 t 

 (1974). U.S. recreational catches 

 are estimated to be two to ten 

 times larger than the commercial 

 catches (Deuel and Clark, 1968; 

 Deuel, 1973; Manooch, 1979; U.S. 

 Dep. Commer., 1984, 1986, 1987). In 

 Mexican waters, commercial land- 

 ings for king mackerel from 1968 to 

 1988 have ranged from 784 t ( 1968) 

 to 6,133 t (Collins and Trent, 1982 1 ). 



Because king mackerel are pres- 

 ently managed in the southeastern 

 U.S. (represented by more than 



eight states and two regional fish- 

 ery management council jurisdic- 

 tions) and support both recre- 

 ational and mixed gear commercial 

 fisheries, the identities of compo- 

 nent stocks are important. Current 

 management of king mackerel fish- 

 eries assumes two migratory stocks 

 with overlapping ranges, one in the 

 U.S. Atlantic Ocean and one in the 

 Gulf of Mexico (Gulf of Mexico and 

 South Atlantic Fishery Manage- 

 ment Councils, 1985). This separa- 

 tion is based on mark-recapture 

 results (Sutherland and Fable, 

 1980; Williams and Godcharles, 

 1984 2 ; Sutter et al., 1991). 



The concept of a stock is one of 

 the most fundamental to fishery 

 management. A stock is variously 

 defined, ranging from the strict 

 definition of a single interbreeding 

 population to a unit capable of in- 



1 L. A. Collins and L. Trent, Natl. Mar. 

 Fish. Serv., Panama City, FL, pers. 

 commun. 1992. 



2 Williams. R. O., and M. F. Godcharles. 

 1984. Completion report, king mackerel 

 tagging and stock assessment. Project 2- 

 341-R. Fla. Dep. Natl. Resour. Unpubl. 

 Rep., 45 p. 



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