500 



Fishery Bulletin 89(3), 1991 



J FMAMJJIASOND 

 Months 



Figure 5 



Percent of Caranx melampygus and Caranx ignobilis found 

 gravid for each monthly sample available (as established by 

 visual gonad classification). Numbers on the figure indicate 

 individual sample sizes. Total sample sizes were 98 C. melam- 

 pygus, all >350mm SL, and 84 C. ignobilis, all >600mm SL. 



ance. Visual gonad stage was the variable we used most 

 often for determining spawning season and SFR. 



Of 98 mature C. melampygus (>350mm SL) com- 

 pared by visual gonad classification, gravid individuals 

 were found from April to November (Fig. 5). In May, 

 June, and July more than half the individuals were 

 gravid. Results from April, August, and September are 

 questionable because sample sizes were small. The 

 GSI's were also plotted against the month of capture 

 to determine spawning season for C. melampygus, with 

 consistent results. Again June and July were the peak 

 months, but there were no gonad samples from which 

 GSI's could be calculated in April or May. A peak in 

 reproductive condition was also visually observed in 

 gonads of mature (>600mm SL) C. ignobilis in sum- 

 mer (Fig. 5). No animals of mature age were caught 

 in December, January, or February, but only 1 of the 

 36 taken from October to April was gravid. 



Among 48 female C. melampygus caught during 

 spawning season (April to October), first reproduction 

 (based on visual gonad classification) appeared to occur 

 between the 325 mm and 375 mm length-classes. In this 

 size range, the percent of gravid individuals increased 

 sharply from 12% to 50%, and at least 50% of all larger 

 females were gravid during these months (Fig. 6). For 

 43 female C. ignobilis caught from May to October, 

 there was a sharp increase from 8% to 62% gravid 

 between the 550 mm and 650 mm length-classes (Fig. 



500 600 



ndard Length (r 



Figure 6 



Size at first reproduction for female Caranx melampygus and 

 Caranx ignobilis. Percent of sampled females found gravid 

 (by visual gonad classification) in each size-class is plotted 

 against standard length. Only fish sampled during summer 

 spawning season are included. Numbers on the figure indicate 

 individual sample sizes. Total sample sizes were 48 C. melam- 

 pygus and 43 C. ignobilis. 



6), and all larger length-classes had a higher incidence 

 of gravid females. Thus, it appears that female 

 C. melampygus reach sexual maturity at about 350 mm 

 SL, and female C. ignobilis at about 600mm SL. 



Fecundity was estimated for C. melampygus from 

 ovaries of 11 gravid females caught in July. The esti- 

 mated fecundity ranged from 49,700 mature ova for 

 a fish of 760 g (328mm SL) to 4,270,000 for one of 

 6490 g (640 mm SL) (Appendix B). A log-linear power 

 function regression was performed in which fecundity, 

 F, in number of eggs, was compared with total wet 

 body weight, W, in grams, and SL, in millimeters. The 

 regression equations are: 



F = 0.923 W 1 - 694 , (r 2 0.84), 



F = 2.286 x 10- 9 (SL) 5 - 359 , (r 2 0.80). 



Diet 



Of 1 18 guts of C. ignobilis examined, 68.6% contained 

 identifiable prey items, which were subjected to quali- 

 tative and quantitative analysis (Table 3). Of the C. ig- 

 nobilis guts with identifiable prey items, 80.3% con- 

 tained the remains of fishes. Parrotfish (Scaridae) were 

 the most important identified family of fish in the diet, 

 occurring in 13.6% of the guts that contained prey. 

 Carangids, most notably the opelu Decapterus maca- 

 rellus, were identified in 8.6% of the guts, and wrasses 

 (Labridae) and bigeyes (Priacanthidae) each occurred 

 in 6.2%. Eels (Anguilliformes: Muraenidae, Congridae, 



