Taylor et al.: Age, growth, maturation, and sex reversal in Centropomus undeamalis 



619 



608 mm in 1995 anci grew to be the largest fish in the 

 study in 1996 (649 mm) but did not reverse sex. At the end 

 of the experiment, the two fish that had reversed sex were 

 the second-and third-largest snook. 



Common snook sex ratios and length-frequency distri- 

 butions were consistent with a diagnosis of protandric her- 

 maphroditism. The overall sex ratio (male to female) for 

 fish on both coasts, over the entire size range, was 1.6:1.0, 

 significantly different from the expected 1:1 (/-=184, df=l, 

 P<0.001). Females smaller than 500 mm were uncommon 

 (4.63'^ of total observed), and only one female smaller 

 than 400 mm was captured. Logistic curves were used 

 to describe length- and age-related shifts in the common 

 snook sex ratio. The predicted length at which 50'^^, of the 

 fish in the population were females was 767 mm on the 

 east coast and 608 mm on the west coast (Fig. 9, Table 5). 

 The predicted age at which 509^ of the fish in the popula- 

 tion were females was 7.4 years on the east coast and 5.1 

 years on the west coast (Fig. 9, Table 5). 



Males reached sexual maturity at 150-200 mm on both 

 coasts. The smallest mature east coast male was 175 mm 

 long and the smallest mature west coast male was 152 

 mm long. The youngest mature male on both coasts was 



age 0. Our sample contained only 13 immature east coast 

 males and 60 immature west coast males. 



Discussion 



We sampled common snook from a variety of fishery-inde- 

 pendent and fishery-dependent sources. Some specimens 

 were donated by recreational anglers, and others were 

 caught by biologists using hook-and-line gear We also used 

 trammel and gill nets and haul seines to capture fish. On 

 the east coast, most of the large common snook we sampled 

 were caught by hook and line during the spawning season 

 from spawning aggregations. In contrast, most west coast 

 samples were collected with seines and trammel nets, and 

 we did not regularly sample west coast spawning aggre- 

 gations. We cannot quantify the potential biases resulting 

 from the use of these different types of gears and sample 

 sources, but our east coast material may have been biased 

 towards larger fish because larger more aggressive individ- 

 uals were harvested with hook and line. Our finding on the 

 east coast of larger and older common snook and of larger 

 observed and predicted lengths at age for most age classes 



