GEOGRAPHIC AND HISTORIC VARIATIONS IN GROWTH OF 



WEAKFISH, CYNOSCION REGAUS, IN 



THE MIDDLE ATLANTIC BIGHT 



Gary Shepherd' and Churchill B. Grimes 2 



ABSTRACT 



The growth of weakfish, Cynoscion regalis, throughout the Middle Atlantic Bight was examined. Six geo- 

 graphic subdivisions were initially established for growth comparisons. Covariate analysis of the total length- 

 scale size relationship revealed three distinct regions. Back-calculated lengths at age were compared using 

 analysis of variance and showed significant differences between regions [I } < 0.001) and between sexes {!'< 

 0.05). Mean lengths at age of northern weakfish were greater than southern fish and females were larger than 

 males after age 6. Maximum mean lengths at age were also greater in the north, 81 cm at age 1 1 , and became 

 progressively smaller towards the south, declining to 42 cm at age 4 in the southernmost region. The growth 

 variations may result from varying allocations of energy to somatic growth according to environmental and 

 migratory requirements. Growth differences resulting from the availability of food items in each habitat are 

 also examined. 



Mean and maximum lengths at age have changed over the past 50 years, with current growth greater than in 

 1929 or 1952. A possible relationship exists between fluctuating population sizes and historic growth 

 variations. The current age/size structure of weakfish fisheries in Delaware Bay is discussed. 



Weakfish, Cynoscion regalis, has been an important 

 fishery resource within the Middle Atlantic Bight 

 since the 19th century (Hildebrand and Schroeder 

 1928). In 1945, arecord41.4 million pounds of weak- 

 fish were landed by commercial interests (Wilk 1981) 

 and, more recently, a recreational fishery has account- 

 ed for an increasing percentage of the total catch 

 (Wilk 1981). Unfortunately, the abundance of weak- 

 fish has not always kept pace with the demand. Com- 

 mercial landings totaled 27.6 million pounds in 1947 

 but declined thereafter, and by 1967 only 3.1 million 

 pounds were caught. Recent landings have in- 

 creased, reaching 28.7 million pounds in 1979 

 (Wilk 1981). 



Weakfish availability to fisheries also fluctuates 

 seasonally due to the migratory nature of the species. 

 In April or May, weakfish migrate into estuaries to 

 spawn (Hildebrand and Schroeder 1928) and are 

 subjected to an inshore fishery. The migratory route 

 is reversed in the fall, with the fish moving to warmer 

 offshore waters (Nesbit 1954). During winter months, 

 an offshore fishery for weakfish operates in the 

 Virginia-North Carolina region (Pearson 1932; Jess 

 Hawkins 3 ). 



'Rutgers University. New Brunswick. NJ 08903; present address: 

 Northeast Fisheries Center Woods Hole Laboratoi-y, National 

 Marine Fisheries Service, NOAA, Woods Hole. MA 02543. 



Rutgers University, New Brunswick, N.J 08903. 



'JessHawkins, NorthCarolina Divisionof Marine Fisheries, Wash- 

 ington, NC 27889, pers. commun. September 1982. 



Despite the importance of weakfish as a commercial 

 resource, relatively little is known about the species 

 migrations or population structure and dynamics. 

 Previous age and growth investigations (Eigenmann 

 1901; Taylor 1916; Welsh and Breder 1923; Nesbit 

 1954; Perlmutter et al. 1956; Daiber 1957; 

 Massmann 1963; Merriner 1973) have generally 

 been localized studies done prior to or during the 

 period of population decline. Following a reduction 

 in population size, as occurred during the 1950's and 

 1 960' s, individual growth rates could theoretically be 

 altered (Beverton and Holt 1957). Geographic 

 variations in growth have also been suggested in pre- 

 vious studies, but were never examined for a single 

 time- series of data (Perlmutter etal. 1956; Merriner 

 1973). This study was undertaken to assess current 

 growth information, examine the variation through- 

 out the Middle Atlantic Bight, and describe any long- 

 term changes in growth that may have occurred. 



METHODS AND MATERIALS 

 Sample Collection 



Samples were collected by the National Marine 

 Fisheries Service (NMFS) groundfish survey from 

 1979 to 1981. All weakfish were captured between 

 Cape Fear, N.C., and Cape Cod, Mass., in depths be- 

 tween 5 and 200 m. Fish were collected with a #41 

 Yankee trawl in the spring and a #36 Yankee trawl in 



Manuscript accepted May 1983. 



FISHERY BULLETIN: VOL. 81, NO. 4. 1983. 



803 



