KATZ ET AL.: DELINEATION OF TILEFISH STOCKS 



Atlantic Bight are in accord with the concept of a 

 separate stock. As we have previously mentioned, 

 they are resident because they are taken year- 

 round in the fishery (Grimes et al. 1980), appar- 

 ently move short distances in the course of a year 

 (Grimes et al. in press), and construct temporally 

 stable burrows that may be occupied for the life 

 of a fish (Able et al. 1982). In addition, they are 

 known to reproduce in the Mid-Atlantic Bight 

 because gonads show seasonal patterns of devel- 

 opment and decline (Idelberger et al. 1981) and 

 eggs and larvae have been collected (Fahay and 

 Berrien 1981). 



The prevailing current patterns and hydro- 

 graphic regimes over the study area are consis- 

 tent with our delineation of the stocks. While 

 there is a southwesterly drift of shelf water with- 

 in the Mid-Atlantic Bight (Miller 1952; Bumpus 

 1973) that would provide mixing of eggs and lar- 

 vae, it is unlikely that egg or larval transport 

 occurs between the Mid-Atlantic and South At- 

 lantic Bights. The Gulf Stream turns eastward 

 at Cape Hatteras so that its axis is located 250 km 

 east of the shelf break in the Mid-Atlantic Bight 

 (Emery and Uchupi 1972). This difference in 

 Gulf Stream effects produces distinct northern 

 and southern continental shelf water masses 

 (Stefansson et al. 1971; Emery and Uchupi 1972). 

 Thus it is unlikely that egg and larval transport 

 between these two areas would commonly occur, 

 although Cox and Wiebe (1979) have suggested 

 that anticyclonic eddies could provide a mech- 

 anism for transporting oceanic larvae across the 

 Gulf Stream to Mid-Atlantic Bight waters. 



Prevailing current systems in the southern 

 United States may provide the means for larval 

 mixing between the Gulf of Mexico and the South 

 Atlantic Bight as suggested by the similarities in 

 allelic frequencies for samples from these two 

 areas. The Gulf of Mexico Loop Current (Maul 

 1977) provides a means for tilefish larvae to be 

 transported out of the Gulf of Mexico and into the 

 South Atlantic Bight as it joins the Florida Cur- 

 rent and eventually forms the Gulf Stream. 



In addition to prevailing currents, periodic 

 mass mortality may have contributed to the dif- 

 ferences between distinct stocks. Following their 

 discovery by a cod fisherman off southern New 

 England in 1879, tilefish experienced a mass 

 mortality in 1882 (a few billion fish reported 

 floating at the surface; Bumpus 1898) probably 

 caused by a sudden temporary intrusion of cold 

 water (McLellan et al. 1953; Hachey 1955). This 

 mortality may have resulted in a "founder effect" 



phenomenon and thus be responsible for stock 

 differences we have noted. 



In summary, we believe that the available data 

 suggest that Mid-Atlantic Bight tilefish popula- 

 tions represent one unit stock and that South 

 Atlantic Bight and Gulf of Mexico populations be 

 considered another stock, at least as a working 

 hypothesis. However, the wide geographic sepa- 

 ration of the latter two areas may necessitate 

 managing them as two stocks. Because the elec- 

 trophoretic results suggest that gene flow may 

 occur between Gulf of Mexico and South Atlantic 

 Bight populations, this should be done with cog- 

 nizance that Gulf of Mexico populations could 

 serve as a source of recruits to South Atlantic 

 Bight populations. 



ACKNOWLEDGMENTS 



This work was initiated upon the urgings and 

 assistance of our friend, the late Lionel Walford, 

 and could not have been accomplished without 

 the cooperation and assistance of other persons 

 whom we wish to gratefully acknowledge. S. 

 Turner and M. Horvath assisted in processing 

 samples. R. Trout provided valuable statistical 

 council and R. Vrijenhoek availed us of his elec- 

 trophoresis facilities and expertise. Fran and 

 Lou Puskus and commercial tilefish fishermen 

 in Barnegat Light, N.J., helped us obtain Mid- 

 Atlantic Bight samples. M. Godcharles, Marine 

 Research Laboratory, Florida Department of 

 Natural Resources, helped us obtain samples 

 from west Florida. Samples from off Texas, 

 South Carolina, and the Yucatan Peninsula 

 (Campeche Bank) were obtained from National 

 Marine Fisheries Service RV Oregon //cruises. 

 Financial support was provided by a New Jersey 

 Sea Grant (R/F-2), a small grant from Rutgers 

 University Research Council, the New Jersey 

 Agricultural Experiment Station (Project No. 

 12409), and the Center for Coastal and Environ- 

 mental Studies, Rutgers University. 



LITERATURE CITED 



Able, K. W., C. B. Grimes, R. A. Cooper, and J. R. Uzmann. 

 1982. Burrow construction and behavior of tilefish, Lo- 

 pholatiluschamaeleonticeps, in Hudson Submarine Can- 

 yon. Environ. Biol. Fish. 7:199-205. 

 Allendorf, F. W., and S. R. Phelps. 



1981. Use of allelic frequencies to describe population 

 structure. Can. J. Fish. Aquat. Sci. 38:1507-1514. 

 Atchley, W. R., C. T. Gaskins, and D. Anderson. 



1976. Statistical properties of ratios. I. Empirical re- 

 sults. Syst. Zool. 25:137-148. 



49 



