FISHERY Bl'LI.ETIN: VOL. 81. NO. 4 



40 



35 



30 



£ 25 



cx 



01 



LL 20 



15 



10 



/\ 



/ 



10 15 20 25 30 35 40 45 



Total Length (cm) 



50 55 



60 



18 



FlGl RE 5.— (Top) size structure of the Cape May, 

 N.J., commercial trawl fishery for weakfish, 

 Cynoscion regalia, in spring and fall 1980-81 and 

 (bottom) size structure of weakfish from 1978-79 

 NMFS groundfish survey catches north of 

 Chesapeake Bay. 



Summer 1979 N= 217 



Fall 1978 N- 13.347 



Fall 1979 N-- 2,62 3 



,.A-J".. 



40 50 



Length (cm) 



60 



70 



80 



Merriner's study of weakfish (1973) in North Car- 

 olina estuaries found only small weakfish, few greater 

 than age 4 and 44 cm which agrees well with our 

 results. Nesbit (1954) and Perlmutter et al. (1956) 

 also noted larger weakfish at northern latitudes. 



Growth variations have been attributed to such fac- 

 tors as density- dependent mechanisms, temperature 

 (Nikolsky 1963), variable energetic costs of migra- 

 tion and spawning (Glebe and Leggett 1981), and 

 variable prey availability (Jones and Johnston 1977). 

 Weakfish seasonal migrations occur in conjunction 

 with movements of the 16°-24°C isotherms (G. 



810 



Shepherd, unpubl. data); therefore, annual variation 

 in temperature encountered by fish in the three 

 regions is inadequate to account for the noted growth 

 differences. We know of no data to indicate that 

 weakfish density varies enough between regions to 

 create drastic growth variations by the compensatory 

 mechanism, although the density of all fish species 

 could be a factor. 



Glebe and Leggett (1981) have shown that growth 

 variations can result if fish in different regions are 

 required to make varying energetic commitments 

 between gonad and somatic growth and seasonal 





