FISHERY BULLETIN: VOL. 82, NO. 3 



aug 

 Month 



FIGURE 3. — Mean monthly gonosomatic indices ±95% C.I. of 

 weakfish, Cynoscion regalis, for 1980 in the New York Bight. N 

 values at each point. 



Mean index values and lengths ±95% C.I. for de- 

 veloping fish in Delaware and Gardiners Bays dur- 

 ing May was 2.48 ± 0.67 at a mean length of 551 ± 

 47.0 mm for females and 1.13 ± 0.85 at a length of 

 391 ± 98.9 mm for males. Spawning fish captured 

 during May had GSI of 8.65 ± 1.64 at mean length 

 of 702 ± 25.2 mm for females and 6.49 ± 1.58 at 

 mean length of 619 ± 33.1 mm for males. In June, 

 spawning fish had mean GSI values of 6.72 ± 1.83 

 with mean length of 544 ±95.6 mm for females 

 and 4.54 ± 1.04 with mean length of 570 ± 56.3 

 mm for males. These index variations confirmed 

 observations of earlier spawning by large fish. 



Seasonal variation in mean HSI of Delaware 

 and Sandy Hook Bay samples indicates that 

 changes in liver weight occurred at the time of 

 spawning and prior to fall migration (Fig. 5). 

 Mean HSI values ± 95% C.I. for females decreased 

 from a high in May of 2.80 ± 0.35 to a low in 

 September of 0.87 ± 0.30. The index values for 

 males followed the same pattern declining from 

 1.89 ± 0.27 in May to 0.96 ± 0.18 in September, but 

 the maximum values occurred in November with a 

 mean HSI of 2.57 ± 0.29. The indices were tested 

 for differences between sexes and the differences 

 were found to be significant in May and June (P < 

 0.001) with the values for females being greater 

 (Table 1). No significant differences were found 

 in a comparison of the July through November 

 samples. 



Frequency distributions of oocyte diameters 

 from 15 fish, ranging from 55 to 81 cm and collected 



TABLE l.— Wilcoxon (Mann-Whitney) test 

 comparing hepatosomatic indices between 

 sexes of weakfish, Cynoscion regalis, from the 

 New York Bight for June through November 

 1980 and May 1981. S = Wilcoxon test 

 statistic, Z = critical value. 



 highly significant differences. 



between 6 May and 22 July show one seasonally 

 progressing mode of developing ova (Fig. 6). The 

 position of the mode varied according to the devel- 

 opment stage of the individual ovary. A sample 

 from 5 May had a mode between 0.02 and 0.45 mm 

 and was skewed toward a prominent peak at 0.12 

 mm. In the 13 May sample, a second mode ap- 

 peared around 0.35 mm and this mode increased to 

 a size of 0.63 mm in the 20 June sample. The 22 

 July sample contained only oogonia. Maximum 

 ova diameter observed was 0.95 mm from a sample 

 on 26 May. That ovum was filled with fluid be- 

 tween the yolk and chorion, indicative of an ova 

 immediately prior to release (Bagenal 1967). This 

 corresponds to the size of weakfish eggs, 0.870- 

 0.975 mm, which have been identified in the water 

 column (Harmic 1958). 



Maturity, Sex Ratio, and Fecundity 



Length ±95% C.I. at which 50% of the total 

 sampled population reached maturity was similar 

 for both sexes. Females attained 50% maturity at 

 25.6 ± 1.2 cm, while males were slightly lower at 

 25.1 ± 1.1 cm (Table 2). The corresponding age at 

 maturity for both sexes was 1 yr. The smallest 

 mature male and female was 20 cm. The 

 maximum size of immature weakfish was 40 cm 

 for females and 33 cm for males. 



The overall population sex ratio approached 

 equality (Table 3). The sex ratio of the population, 

 divided into 5 cm length intervals, was 48:52 

 females to males and was not significantly differ- 

 ent from 50:50 as determined from a chi-square 

 analysis ( x 2 = 1.81, x 2 o.o5 = 3.84, n = 1,669). Sex 

 ratio at size data did reveal significant differences 

 from 50:50 for several length intervals. At 40 cm, 

 the ratio was 52:48 female to male but increased to 



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