364 



Fishery Bulletin 88|2). 1990 



VII VIII IX 

 Age (years ) 



XII XIII XIV 



Figure 3 



Growth (mean back-calculated fork lengths) of Scomberomorus canal- 

 la (a) males and (b) females. 1 = Northeastern Brazil (Ximenes et al. 

 1978); 2 = Northeastern Brazil (Nomura and Rodrigues 1967), ages 

 III and above observed lengths; 3 = Trinidad, this study; 4 = U.S. 

 Gulf of Mexico (Manooch et al. 1987); 5 = Southeastern U.S., excl. 

 La. (Johnson et al. 1983); 6 = Florida (Beaumariage 1973), fork length 

 transformed from standard length by his formula FL = 1.096SL - 

 17.143; 7 = Southeastern U.S. incl. La. (Johnson et al. 1983). 



States and northeastern Brazil. For both sexes, there 

 is wide separation of lengths at age I, with those of 

 Trinidad and North American fish being larger than 

 those of Brazilian fish. The largest male lengths are 

 from the Florida sample (Beaumariage 1973) up to age 

 IV, and the smallest are for fish sampled in Brazil by 

 Nomura and Rodrigues (1967) up to age VI. For fe- 

 males, the largest lengths are again for Beaumariage's 

 sample except for an anomalous population of large 

 females sampled in Louisiana (Johnson et al. 1983), and 

 the smallest lengths are similarly for Nomura and 

 Rodrigues' Brazilian sample. Back-calculated lengths 

 at age of Trinidad fish lie between the larger lengths 

 of North American fish and the smaller lengths of 



Brazilian fish, up to age III for males (82.8% of the sam- 

 ple) and age V for females (91.9% of the sample). The 

 growth curve of Trinidad males closely resembles those 

 from the southeastern United States presented by 

 Johnson et al. (1983) and Manooch et al. (1987) up to 

 age V, whereas the growth of Trinidad females is more 

 simOar to that of BrazOian females sampled by Ximenes 

 et al. (1978). Growth rates of males from the different 

 areas are similar up to age II, with Brazilian males 

 showing less incremental decrease in the later ages. 

 The same trend is shown for females, with marked in- 

 cremental decrease being shown by southeastern 

 United States (excluding Louisiana) females sampled 

 by Johnson et al. (1983). 



The von Bertalanffy growth parameters of Trinidad 

 S. cavalla are presented in Table 2 along with those 

 from southeastern United States and Brazil. Asymp- 

 totic lengths are larger for females than males. The 

 asymptotic lengths of Trinidad and Brazil males are 

 close, and much larger than those from North America, 

 except for the recent study from the Gulf of Mexico 

 (Manooch et al. 1987). For females, the pattern is some- 

 what similar, with the Trinidad and Gulf of Mexico 

 values being the largest, except for the additional sam- 

 ple of large females from Louisiana (Johnson et al. 

 1983). For both sexes the K values are fairly close, the 

 lowest coming from Trinidad, Brazil, and the Gulf of 

 Mexico, with again the exception of the Louisiana 

 females. 



Size and age at first maturity 



There were 14 ripe males (11 ripe -i- three ripe-running) 

 and three ripe females in the age-I group, indicating 

 first spawning for both sexes to take place in this age 

 group. The shortest ripe male was 54.5 cm, and the 

 largest immature developing male was 80 cm. The 

 shortest ripe female was 58.5 cm, and the largest im- 

 mature developing female was 114.5 cm. These sizes 

 at maturity indicate that first spawning for both sexes 

 may also take place at age II (Table 1). 



Gonad analysis and GSI 



Gonad stages and corresponding GSI values are shown 

 in Table 3. No ripe-running females nor spent fish were 

 observed in this study. Figures 4 and 5 show gonad 

 analysis of the 97 males and 224 females that were 

 capable of spawning as indicated by size at first matur- 

 ity. Of these, 70 males and 164 females were analyzed 

 for GSI, and the results are also shown in Figures 4 

 and 5. Male gonad analysis was more difficult because 

 milt was present in the early stages of gonad develop- 

 ment; this explained the trend to higher percentages 

 of ripe males. Ripe fish were present during all months 



