STOCK IDENTIFICATION OF WEAKFISH, CYNOSCION REGALIS, 

 IN THE MIDDLE ATLANTIC REGION 



Maurice K. Crawford/ Churchill B. Grimes, ^ and 

 Norman E. Buroker' 



ABSTRACT 



The hypothesis that a single stock of weakfish. Cynoseiun regalis, existed in the Middle Atlantic was 

 tested. Using starch gel electrophoresis we identified two polymorphic loci (6-phosphogluconate dehy- 

 drogenase and malate dehydrogenase) out of a total of 25 protein loci surveyed. Statistical analysis of 

 allelic frequencies revealed that the populations were statistically indistinguishable. 



Weakfish, Cynoscion regalis, commonly reach sizes 

 between 70 and 80 cm in length and 3.0 and 4.5 kg 

 in weight. They occur from Cape Cod, MA to Florida 

 but are most common in the Middle Atlantic region 

 (Wilk 1979). Weakfish participate in a spring spawn- 

 ing migration into bays and estuaries. In the fall, 

 the migrations reverse and fish move either offshore 

 or to more southern waters to overwinter (Welsh 

 and Breder 1923; Bigelow and Schroeder 1953; Wilk 

 1979). Spawning occurs from May to mid-July in 

 northern estuaries (e.g., Delaware Bay and Gardi- 

 ners Bay, NY; Shepherd and Grimes 1984) and from 

 March to September in more southern waters (e.g.. 

 North Carolina; Merriner 1976). 



Weakfish are an important commercial and rec- 

 reational species and historically landings have fluc- 

 tuated widely. From 1940 to 1949, commercial land- 

 ings averaged 8,800 metric tons (t), with a high of 

 18,800 t in 1945. Between 1950 and 1969, annual 

 catches declined to an average of 2,600 t, but a 

 resurgence occurred when the catches rose to a 

 7,700 t average between 1970 and 1979 (Wilk 1981). 



Recreational landings of weakfish have been sim- 

 ilarly variable, and in some years have been esti- 

 mated to be as large as the commercial landings 



'Department of Horticulture and Forestry, Cook College, Rut- 

 gers University, New Brunswick, NJ 08903; present address: 

 School of Forest Resources, University of Georgia, Athen. GA 

 30602. 



^Department of Horticulture and Forestry, Cook College, Rut- 

 gers University, New Brunswick, NJ 08903; present address: 

 Southeast Fisheries Center Panama City Laboratory, National 

 Marine Fisheries Service, NOAA, 3500 Delwood Beach Road. 

 Panama City, FL 32408. Reprint requests should be sent to the 

 second author (CBG) at the present address. 



'Department of Zoology, Rutgers University. New Brunswick, 

 NJ 08903; present address: Department of Pediatrics RR20. 

 School of Medicine, University of Washington, Seattle, WA 

 98195. 



(Murawski 1977). In 1965, catches only amounted 

 to 1,000 t but increased to 7,100 t in 1970 (Wilk 

 1981). In 1974, recreational landings were approx- 

 imately 9,100 t, or about 60% of the estimated total 

 catch (Murawski 1977). Landings dropped to 5,000 

 t in 1979, and Middle Atlantic states accounted for 

 95% of the catch (Wilk 1981). 



Several studies (Nesbit 1954; Perlmutter et al. 

 1956; Seguin 1960) have concluded that there were 

 multiple stocks of weakfish in the Middle Atlantic 

 region based upon mark recapture, scale circuli 

 spacing, and morphological data, respectively. More 

 recent studies have shown geographic differences 

 in growth and reproduction of weakfish between 

 Cape Cod, MA and Cape Hatteras, NC (i.e., north- 

 ern fish lived longer, grew larger, and had a lower 

 relative fecundity than southern fish; Shepherd and 

 Grimes 1983, 1984). These life history differences 

 could be due to environmental effects or could be 

 indicative of discrete stocks (Shepherd and Grimes 

 1983). We hypothesized that a single panmictic pop- 

 ulation of weakfish exists in the Middle Atlantic 

 region. In order to test this hypothesis, starch gel 

 electrophoresis was used to identify protein varia- 

 tion for two polymorphic structural loci (malate 

 dehydrogenase-2 and 6-phosphogluconate dehydrog- 

 enase) found among weakfish in this region. 



MATERIALS AND METHODS 



We sampled adult and juvenile (young-of-year) 

 weakfish along the east coast of the United States 

 from Buzzards Bay, MA to Cape Hatteras, NC (Fig. 

 1). Adult fish were caught in the fall of 1982 and 

 summer of 1983 by the National Marine Fisheries 

 Service bottom trawl survey cruises (Grosslein 

 1969). We also purchased adults in some locations 



Manuscript accepted October 1988. 

 Fisherj- Bulletin, U.S. 87:205-211. 



205 



