491 



Abstract-A total of IOO6 king mack- 

 erel iScarnheromorus cavalla) repre- 

 senting 20 discrete samples collected be- 

 tween 1996 and 1998 along the east 

 (Atlantic) and west (Gulf) coasts of Flor- 

 ida and the Florida Keys were assayed 

 for allelic variation at seven nuclear- 

 encoded microsatcllites. No significant 

 deviations from Hardy-Weinberg equi- 

 librium expectations were found for six 

 of the microsatellites, and genotypes at 

 all microsatellites were independent. 

 Allele distributions at each microsatel- 

 lite were independent of sex and age of 

 individuals. Homogeneity te.sts of spa- 

 tial distributions of alleles at the micro- 

 satellites revealed two weakly divergent 

 "genetic" subpopulations or stocks of 

 king mackerel in Florida waters — one 

 along the Atlantic coast and one along 

 the Gulf coast. Homogeneity tests of 

 allele distributions when samples 

 were pooled along seasonal (temporal) 

 boundaries, consistent with the tem- 

 poral boundaries used currently for 

 stock assessment and allocation of the 

 king mackerel resource, were nonsig- 

 nificant. The degree of genetic diver- 

 gence between the two "genetic" stocks 

 was small: on average, only 0.19% of 

 the total genetic variance across all 

 samples assayed occurred between the 

 two regions. Cluster analysis, assign- 

 ment tests, and spatial autocorrelation 

 analysis did not generate patterns that 

 were consistent with either geographic 

 or spatial-temporal boundaries. King 

 mackerel sampled from the Florida 

 Keys could not be assigned unequivo- 

 cally to either "genetic" stock. The gen- 

 etic data were not consistent with cur- 

 rent spatial-temporal boundaries em- 

 ployed in stock assessment and allo- 

 cation of the king mackerel resource. 

 The genetic differences between king 

 mackerel in the Atlantic versus those 

 in the Gulf most likely stem from 

 reduced gene flow (migration) between 

 the Atlantic and Gulf in relation to gene 

 flow (migration) along the Atlantic and 

 Gulf coasts of peninsular Florida. This 

 difference is consistent with findings 

 for other marine fishes where data indi- 

 cate that the southern Florida penin- 

 sula serves (or has served) as a biogeo- 

 graphic boundary. 



Population structure of king mackerel 



(Scomberomorus cavalla) 



around peninsular Florida^ 



as revealed by microsatellite DNA* 



John R. Gold 



Elena Pak 



Center for Biosystematics and Biodiversity 



Department of Wildlife and Fisfneries Sciences 



Texas A&M University 



College Station, Texas 77843-2258 



E mail address (for J R Gold) goldfishiaitamu edu 



Doug A. DeVrles 



National Manne Fisheries Service 

 Southeast Fisheries Science Center 

 3500 Delwood Beach Road 

 Panama City, Flonda 32408 



Manuscript accepted 4 March 2002. 

 Fish. Bull. 100:491-.509 (2002). 



The king mackerel (Scornberomorufi ca- 

 valla) is a coastal pelagic fish distrib- 

 utee] in the western Atlantic Ocean from 

 Massachusetts (USA) to Rio de Janeiro 

 (Brazil) and in the Gulf of Mexico and 

 Caribbean Sea (Rivas, 1951; Collette 

 and Nauen, 1983). Recreational and 

 commercial catches of king mackerel in 

 U.S. waters are substantial (Manooch, 

 1979; MSAPi; Legault et al.^) and the 

 species is critical to the southeastern 

 Atlantic coast (hereafter "Atlantic") 

 and northern Gulf of Mexico (hereafter 

 "Gulf) charter-boat industries. Man- 

 agement of the king mackerel resource 

 in U.S. waters is under the jurisdiction 

 of two regional fishery management 

 councils, and current management 

 planning (GMFMC-^) is based on a two 

 migratory unit (stock) hypothesis: one 

 stock (Atlantic migratory unit) occurs 

 in the U.S. southeastern Atlantic, the 

 other (Gulf of Mexico migratory unit) 

 occurs in the Gulf Separation of the 

 two stocks has been based primarily 

 on mark-and-recapture studies carried 

 out prior to 1984 and on differences in 

 growth rate (MSAP'; Williams and God- 

 charles^). Based on the mark-and-recap- 

 ture studies, it was hypothesized that 

 the two stocks mixed extensively during 



* This is paper 34 in the series "Genetic 

 Studies in Marine Fishes" and is contribu- 

 tion 98 of the Center for Biosystematics 

 and Biodiversity, Texas A&M University, 

 College Station, Texas 7784.3-2258. 



' MSAP ( Mackerel Stock Assessment Panel ). 

 1994. Contribution report of the mackerel 

 stock assessment panel. Contribution re- 

 port MlA-93/94-42, 27 p. Southeast Fish- 

 ery Science Center, National Marine Fish- 

 eries Service, 75 Virginia Beach Dr., Miami, 

 FL 33149. 



- Legault, C. M., M. Ortiz, G. Scott, N. Cum- 

 mings, and P. Phares. 2000. Stock as- 

 sessment analyses on Gulf of Mexico king 

 mackerel. Contribution report SFD-99/ 

 00-83, 48 p. Southeast Fishery Science 

 Center, National Marine Fisheries Service, 

 75 Virginia Beach Dr., Miami, FL 33149. 



* GMFMC (Gulf of Mexico Fishery Manage- 

 ment Council). 1996. Amendment 8 to 

 the fishery management plan for coastal 

 migratory pelagic resources in the Gulf of 

 Mexico and South Atlantic includes envi- 

 ronmental assessment, regulatory impact 

 review, and initial regulatory flexibility 

 analysis. Gulf of Mexico Fishery Manage- 

 ment Council, 3018 U.S. Hwy 301 North, 

 Suite 1000, Tampa, FL 33619-2266. 



^ Williams,R.O.,andM.FGodcharles. 1984. 

 Completion report, king mackerel tagging 

 and stock assessment. Project rep. 2- 

 341-R, plus figures and tables., 45 p. FL 

 Dept. Nat. Res., Florida Marine Research 

 Institute, 100 8"^ Ave. SE, St. Petersburg, 

 FL 33701. 



