246 



Fishery Bulletin 9 1(2), 1993 



with postovulatory follicles, indicating onset of 

 spawning and possible shedding of eggs, were 

 eliminated from further analysis of fecundity. To 

 determine the precision of batch fecundity meth- 

 odology (Hunter et al. 1985), we compared oo- 

 cyte counts per unit weight within ovaries using 

 a two-way analysis-of-variance model, SAS GLM 

 procedure (SAS 1985). 



Results 



Sampling, sex ratio, and maturity 



We recorded information on length, sex, and gear 

 for 236 male, 108 female, and 36 immature black 

 drum. In addition, we collected capture data, ovar- 

 ian samples, and measurements, including somatic 

 and gonad weights used for GSI analysis, from 

 198 males and 296 females. Ovarian histology sec- 

 tions were made from 234 mature females ran- 

 domly sampled through June 1987, and were used 

 to determine relative frequencies of oocyte stages 

 (Fig. 1). Of these females, 25 were visibly hy- 

 drated, possessed no postovulatory follicles, and 



100 -, 



o 



100 



H 



3.8 3.8 



8 ° 



O 100 



ra 



35.3 



45.6 



28.9 



3.7 







18.5 17.3 1n . 

 ^3 « ^ ^ 1 M „ ^ ^ 



93.3 ?S=9 



-,¥£ 91.5 



i 



PG 



64.9 



liiiliil 



Oct Nov Dec Feb Mar Apr May Jun 

 1986 1987 



Figure 1 



Percent oocyte stage by month for 1986-87 based on 

 point counts of -200 oocytes/female black drum 

 Pogonias cromw. Stages include primary growth (PG), 

 cortical alveolar (CA), vitellogenic (V), and hydrated 

 (H). Number of females examined = 22 Oct, 23 Nov, 

 23 Dec, 69 Feb, 32 Mar, 24 Apr, 22 May, 19 June. 



were used to estimate batch fecundity. Our sample mean 

 length was 761mmFL, with adults measuring 650- 

 900 mmFL comprising 89% of individuals used in the study. 



We found apparent differences in sex ratios from inshore 

 landings (gillnet and haul-seine) and landings from an 

 offshore trawl fishery during the reproductive season 

 (Table 1). Trawl catches were dominated by males, while 

 gillnet and haul-seine samples were dominated by females 

 (Table 1). For months just before and after the reproductive 

 season (October, June, July), females also dominated gillnet 

 and haul-seine landings, but ratios were less divergent. The 

 trawl fishery was not active at these times, but samples of 

 offshore fish were taken from a purse-seine landing (June 

 1986) and numbers of females and males were nearly equal 

 (0.92:1.0). We applied a x' 2 contingency analysis to test sex 

 ratios by gear type. The x 2 statistic was significant during 

 the reproductive season (December-May), leading to rejec- 

 tion of the null hypothesis that gear type and sex ratio are 

 independent (Table 1). We assumed that gears were not 

 selective for sex but reflected actual sex ratios in the locali- 

 ties fished. Therefore, the skewed sex ratio suggests a seg- 

 regation of sexes during the reproductive period. Female: 

 male ratios were more divergent for commercial gears dur- 

 ing the months of November-May than October, June, and 

 July (Table 1). 



Males and females were first mature at 600-640 mmFL 

 as defined by the size at which individuals exhibit develop- 

 ing and mature gonads from gross visual inspection (Nielsen 

 & Johnson 1983). All black drum >640mm were mature. 

 All fish <590 mm were immature, but sample size during 

 spawning season was small (n = 18 females and 11 males at 

 460-590 mm). 



