FISHERY BULLETIN: VOL. 82, NO. 3 



opment of ovaries demands higher energetic costs 

 than testicular development (Nikolsky 1963); 

 therefore, the necessary energy reserves in the 

 liver would be proportionately larger in females 

 (Timashova 1982). After spawning, the sexual 

 dimorphism disappears and HSI values for 

 both sexes increase similarly prior to the fall 

 migration. 



The peak spawning period in the New York 

 Bight estuaries varied with different size 

 weakfish. Generally, among migratory fishes, the 

 larger individuals will return to an estuary prior 

 to their smaller counterparts (Briggs 1955; 

 Nikolsky 1963). Weakfish exhibit a similar behav- 

 ior, as the largest individuals or "tiderunners" 

 enter the bays in early May and spawn by mid- 

 May, whereas the smaller weakfish arrive later 

 and reach peak spawning during June. The GSI 

 values for fish > 60 cm generally decline from May 

 to June, while smaller fish increase to maximum 

 values in June. This differential spawning based 

 on parental size results in two spawning peaks and 

 the subsequent appearance of bimodal length- 

 frequency data for juvenile weakfish (Daiber 1954; 

 Thomas 1971; Shepherd and Grimes 1983). 



Sex Ratio, Maturity, and Fecundity 



The overall sex ratio of the population is not 

 different from 1:1, but one sex was dominant at 

 certain length intervals. We believe the deviations 

 from a 1:1 ratio at various lengths were attribut- 

 able to differential growth between sexes ( Wenner 

 1972). Female growth begins to exceed male 

 growth at about 45-55 cm (Shepherd and Grimes 

 1983), at which point the sex ratio becomes domi- 

 nated by males. Females grew beyond that size 

 interval faster and occupied the majority of the 

 60-85 cm length intervals. Although males have 

 growth potential equal to females, the numbers 

 attaining maximum size were greater for females. 



In northern waters, the size at which weakfish 

 attained 50% population maturity was similar for 

 both sexes. Females matured by 25.6 cm at age 1 

 while males attained maturity at 25.1 cm, also at 

 age 1. Apparently, greater differences exist be- 

 tween northern weakfish (Delaware Bay and 

 north) and southern weakfish (North Carolina). 

 Although ages were similar, southern females 

 spawned at 23 cm and males by 18 cm (Merriner 

 1973). 



Estimates of fecundity for New York Bight 

 weakfish differ from estimates for southern 

 weakfish. Weakfish in North Carolina did not 



reach sizes much beyond 45 cm but had fecun- 

 dities, relative to length, several times higher 

 than northern weakfish (Merriner 1976) (Table 5). 

 For example, at 50 cm TL female weakfish from 

 New York Bight produced 306,159 ova, while the 

 fecundity of southern fish of the same size was 

 2,051,080 ova. In spite of these large differences, 

 lifetime fecundity would be approximately equal. 

 Southern weakfish can potentially reproduce until 

 age 5 and produce about 9,913,080 ova (based on 

 the equation, fecundity = 0.152 TL? 6418 , from Mer- 

 riner 1976), whereas northern weakfish reproduc- 

 ing for 10 yr have nearly equivalent total ova pro- 

 duction of 10,008,167. 



Batch spawning, involving two distinct groups 

 of ova, was found for weakfish in North Carolina 

 (Merriner 1976). In samples examined in 1980-81 

 from Delaware and Gardiners Bays, multiple 

 spawns were not evident. The ova diameter fre- 

 quencies of developing and ripe ovaries contained 

 two modes, one consisting of reserve oocytes and 

 another of developing ova. The developing ova had 

 a wide size range ( — 0.3 mm) and may have been 

 released during consecutive spawning events, but 

 did not constitute separate batches within an ov- 

 ary. Furthermore, all ova produced annually by 

 weakfish may not be released during spawning. A 

 study of Delaware Bay weakfish in 1954 proposed 

 batch spawning, but spent ovaries were not 

 examined to determine if all ova were released 

 (Daiber 1954). Ovaries classified as spent which 

 we examined still contained 25-40% of the ova 

 expected for a fish of that size. These results 

 suggest fertility may be 60-75% of estimated po- 

 tential fecundity. Foucher and Beamish (1980) re- 

 ported similar conclusions from studies of Pacific 

 hake, Merluccius productus. We did not examine 



TABLE 5. — Comparison of fecundity for weakfish, 

 Cynoscion regalis, between Cape Hatteras (Merriner 

 1976) and New York Bight. 



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