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Fishery Bulletin 92(1), 1994 



in the summer. These authors also tagged fish off 

 North and South Carolina, but none were recovered 

 in the Gulf. 



According to Fable et al. (1990), 4 king mackerel 

 tagged in northwest Florida have been recovered in 

 south Florida. Typically, these are the smallest and 

 youngest tagged in the southeast United States. 

 Sutherland and Fable ( 1980) showed that northeast 

 Gulf fish migrated to south Florida. However, addi- 

 tional tagging (Fable et al., 1990 4 ) showed that 

 northeast Gulf fish eventually moved westward to 

 Louisiana, Texas, and Mexico waters when they had 

 been free for a sufficient time and grown to a larger 

 size. 



Tagging off Louisiana from 1983 to 1985 (Fable 

 et al., 1987) indicated that the northwest Gulf may 

 have year round residental large king mackerel that 

 mix in the warm months with smaller migrants 

 from south Florida and Mexico. Recent tagging data 

 (Fable et al., 1990 4 ) from this region have provided 

 additional recoveries from both south Florida and 

 Mexico, strengthening this interpretation. Addi- 

 tional support is provided by the occurrence in Loui- 

 siana of a year-round king mackerel fishery, whereas 

 elsewhere the fishery is seasonal. 



In contrast to historical reports, recent tagging 

 (Fable et al., 1990 4 ) showed movements between 

 Texas and Mexico. Fish tagged in Texas waters mi- 

 grate to both Florida and Mexico. Additionally, fish 

 movements between Texas and eastward (as far as 

 Panama City, FL) were documented. 



Mark-recapture data (Fable et al., 1990 4 ) from 

 tagging in Mexican waters suggest that the states 

 of Campeche and Yucatan are wintering areas for 

 king mackerel in the western Gulf. Fish tagged in 

 warmer months (April-July) in Texas, Tamaulipas, 

 and Veracruz were found in Campeche and Yucatan 

 in the winter. Tagging efforts (Fable et al., 1990 4 ) 

 in Veracruz have provided evidence of northward mi- 

 grations to Tamaulipas and Texas in spring and sum- 

 mer, and movement to the Yucatan peninsula in winter. 



Additional evidence supporting two Gulf stocks 

 can be found in catch-effort data of king mackerel. 

 Although the data are complicated by different fish- 

 ing strategies depending on the type of fishery (rec- 

 reational or commercial) and regulatory closures, 

 detailed analysis of catch data from the southeast- 

 ern United States charterboat fishery indicated that 

 in spring and early summer some stocks of fish si- 

 multaneously migrated northward along the west- 

 ern and eastern coasts of the Gulf (Trent et al., 

 1987b). They also developed the ". . . idea that part 

 of the population of large fish remains in the Loui- 

 siana area year-round and that the abundance of 

 these fish is greatest during cold months." 



The fishery for king mackerel in Louisiana is 

 unique among the fisheries in the northern Gulf of 

 Mexico in that it is year-round; elsewhere it takes 

 place mainly from late spring to late fall. The win- 

 ter fishery (commercial hook-and-line) in Louisiana 

 began in 1981-82. Distinctive differences character- 

 ized winter and spring-fall seasons: 1) the smallest 

 fish (both males and females) were caught April to 

 October whereas the largest fish were caught be- 

 tween November and March; 2) females were more 

 abundant in the winter fishery than at other times 

 of the year (Trent et al, 1987a). 



For two or more populations to maintain separate 

 identities they must be isolated, either physically or 

 reproductively (Hartl, 1980). In the case of Gulf king 

 mackerel, there is evidence for reproductive isola- 

 tion. Grimes et al. (1990) presented a detailed ex- 

 amination of the distribution and occurrence of lar- 

 val and juvenile king mackerel in the Gulf (based 

 on published reports, neuston sampling, and Mexi- 

 can trap net and trawl collections). The spawning 

 season in the northern Gulf (U.S. waters), as indicated 

 by the seasonal occurrence of larvae, is May to Octo- 

 ber. Larval collections off Mexico were sparse and of- 

 fered little information on spawning seasonality. 



The summer spawning period in the northern 

 Gulf was also indicated by seasonal gonadal devel- 

 opment of king mackerel (Finucane et al., 1986). 

 They reported that reproductive activity occurred 

 from May through September; a few fish were re- 

 productively active as early as April and as late as 

 October. However, spawning dates of January 

 through August for Mexican juveniles estimated 

 from otolith data showed a bimodal distribution, 

 which suggests that spawning seasons in Mexican 

 waters are different from those in the northern Gulf 

 (Grimes et al., 1990). 



Two of the four collections of juvenile king mack- 

 erel in Mexico used by Grimes et al. ( 1990) had tis- 

 sue samples (Tampico, July 1986, and Playa Norte, 

 Sept. 1986), and we analyzed these samples for 

 PEPA-2* variation. Spawning dates of fish in the 

 Tampico collection ranged from mid-February to 

 mid-April and PEPA-2' a frequency was 0.896. The 

 Playa Norte collection's spawning dates ranged from 

 mid-April to mid-July and PEPA-2* a frequency was 

 0.600 (Table 1). 



Water circulation data for the Gulf of Mexico 

 (Salsman and Tolbert, 1963 7 ) and information from 

 Trent et al. (1987b), Grimes et al. (1990), Fable et 

 al. 1990, 4 along with our data on king mackerel, sug- 



7 Salsman, G. G., and W. H. Tolbert. 1963. Surface currents in 

 the northeastern Gulf of Mexico. U.S. Navy Mine Defense 

 Laboratory, Panama City, FL, Res. and Dev. Rep. 209, 43 p. 



