SHEPHERD and GRIMES: REPRODUCTION OF WEAKFISH 



2250 



1750 



o 1250 



-o 750 



3 



250 



350 



450 550 



Length (mm) 



650 



750 



FIGURE 7. — Fecundity as a function of length for weakfish, Cynoscion regalis, in New 



York Bight for 1981. 



In fecundity = -16.322 + 4.659 In total length 



(mm) ±0.368 



r 2 = 0.835 n = 28 Figure 7 

 In fecundity = 1.975 + 1.542 In gutted weight 



(g) ± 0.364 



r 2 = 0.839 n = 28. 



Fecundities were also estimated for six weakfish 

 collected in June from Gardiners Bay which ap- 

 peared to be spent, although they had ova remain- 

 ing in the gonad. These ova were 0.55 to 0.65 mm 

 which were similar in size to those present in a 

 ripe ovary. All six samples were significantly dif- 

 ferent (P < 0.001) than expected values based on a 

 Students t~test (Table 4). These June samples were 

 60-75% lower than the predicted fecundities at 

 length. 



DISCUSSION 



Weakfish spawning in northern estuaries is a 

 seasonal event which occurs following the spring 

 inshore migration. (Welsh and Breder 1923; Hil- 

 debrand and Schroeder 1928). Our study found the 

 spawning period for weakfish in Delaware Bay 

 and Gardiners Bay, as determined from maturity 

 stages, to be from May to mid-July Ichthyoplank- 

 ton surveys have found weakfish eggs and larvae 

 present in New York Bight from May to July (Col- 

 ton et al. 1979). The spawning period was further 

 substantiated by changes in GSI. The mean GSI 

 values reached a maximum in May for males and 

 in June for females, then both declined to mini- 



TABLE 4. — Difference between expected fecundity 

 (based on In fee = -16.322 + 4.659 In TL) and ob- 

 served fecundity for 6 weakfish, Cynoscion regalis, 

 collected 27 June 1981, in Gardiners Bay, N.Y. 



mum values by August. The gonad weights were 

 maintained at this low level until the fish disap- 

 peared from the coast in late November. The 

 spawning period of weakfish in North Carolina is 

 somewhat longer, extending from March to Sep- 

 tember with the peak period from April to June 

 (Merriner 1976). The duration of the ripe maturity 

 stage in Delaware and Gardiners Bays was 

 greater for males, with ripe males captured as late 

 as 22 July. The protracted spawning season of 

 males was also evident in the GSI values. July was 

 the only month in which male indices were greater 

 than those of females, indicating that the gonad 

 weight per unit body weight was larger in males. 

 In other months, female GSI values were as much 

 as 2.8% greater than males. 



Sex differences were also evident in physiologi- 

 cal changes associated with spawning. HSI values 

 were near maximum in May, during spawning 

 season, and as expected higher in females. Devel- 



507 



