296 



Fishery Bulletin 98(2) 



lepis. Hood and Schlieder, 1992; E. guttatus, Sadovy 

 et al., 1992). In the southern United States, the yel- 

 lowedge grouper has a lower asymptotic length and 

 higher growth rate {L^=891mm TL, if =0.163, Keener, 

 1984; L„=831 mm TL, X=0.191, Bullock and God- 

 charles^) than those found in our study. Our maxi- 

 mum observed age (35 years) was greater than those 

 (15 and 27 years) reported by Keener ( 1984) and Bull- 

 ock and Godcharles,'^ respectively. 



Comparison of gi'owth curves using <J>', where = 

 logiiL + 21ogL„ (Munro and Pauly, 1983; Pauly and 

 Munro, 1984) showed close agreement with those in 

 other areas ( 0=2.96, our study, 0=3. 11 and 3.12, south- 

 em United States with growth parameters of Keener, 

 1984, and Bullock and Godcharles'\ respectively). This 

 comparison suggests that the general growth pattern 

 of yellowedge grouper observed in our study is similar 

 to that for the southern United States and further vali- 

 dates the results obtained in our study. 



The yellowmouth grouper also showed a higher 

 L^ (854 mm FL or 934 mm TL) and lower K than 

 reported for the eastern Gulf of Mexico where L,, was 

 828 mm TL and K was 0.076 (Bullock and Murphy, 

 1994). The maximum observed age (41 years) was 

 higher than that (28 years) reported by Bullock and 

 Murphy (1994). Comparison of growth curves using 

 'showed close agreement between the growth curve 

 obtained in our study (<f>'=2.70) and that obtained 

 by Bullock and Murphy ( 1994) whose gi-owth param- 

 eters resulted in <J>of 2.72. 



Results suggest that the growth curve of each spe- 

 cies belongs to the same family of curves as their 

 counterparts in other geographical areas, i.e. the 

 relationship between L. and K is similar (Pauly, 

 1991). However, comparison of actual growth rates 

 and asymptotic lengths indicates that each species 

 grows slower and achieves a greater size and age 

 than those reported for populations in the southern 

 United States. This finding is in contrast to what is 

 expected in the growth patterns of tropical versus 

 subtropical and temperate populations. Tropical fish 

 generally grow faster and reach smaller sizes than 

 populations in higher latitudes, mainly because of dif- 

 ferences in environmental temperature (Longhurst 

 and Pauly, 1987). It appears that factors other than 

 those related to the environment may be responsible 

 for the differences observed, or may mask the real 

 growth pattern. Such factors may include intrinsic 

 differences between populations, or differences in 

 fishing patterns between the two areas. The latter 

 may contribute significantly to differences in growth 

 because grouper populations in the southern United 

 States have been fished since the late 1970s (Bullock 

 and Murphy, 1994; Bullock et al, 1996) for a longer 

 period of time than the populations in our study. Pop- 



ulations subjected to high exploitation rates for long 

 time periods generally exhibit changes in growth 

 and reproductive patterns, such as faster growth 

 and smaller sizes (Gulland, 1983), as well as smaller 

 size at maturity (McGovern et al., 1998) than popu- 

 lations that have not been as heavily fished. 



The slow growth, long life spans, and presumed 

 low natural mortality rates of yellowedge and yellow- 

 mouth gi'ouper reported for our study, imply that they 

 are highly susceptible to overfishing (Bullock et al., 

 1992). These characteristics suggest that maximum 

 yield would be obtained at either low exploitation 

 rates or with capture of only large individuals (Bull- 

 ock et al., 1992). In addition, the protogynous her- 

 maphroditic strategy of some groupers may also make 

 them more susceptible to overfishing than gonocho- 

 ristic species (Bannerot et al., 1987). Evidence of her- 

 maphroditism has been reported for the yellowedge 

 grouper (Keener, 1984; Bullock et al., 1996) and other 

 species of Mycteroperca (Matheson et al., 1986; Col- 

 lins et al., 1987; Hood and Schlieder, 1992; Crabtree 

 and Bullock, 1998). We did not consider differences 

 in growth patterns and population dynamics specific 

 to an alternative reproductive strategy in our study. 

 For protogynous hermaphrodites, the pooling of data 

 for combined sexes may mask certain growth pat- 

 terns such as enhanced growth rates following sexual 

 transition and could lead to errors in the predictions 

 obtained from standard yield models (Bannerot et al., 

 1987). Thus, subsequent studies should consider the 

 effects of an alternative reproductive strategy on pop- 

 ulation parameters and the predictions for manage- 

 ment of these species in Trinidad and Tobago. 



Acknowledgments 



This project was accomplished with financial and 

 technical assistance from the United Nations Devel- 

 opment Programme and the Food and Agricultural 

 Organization. The authors wish to thank the fol- 

 lowing: Edward Brothers for assistance with otolith 

 reading; Daniel Pauly for technical advice; Maxwell 

 Sturm for reviewing earlier drafts of the manuscript; 

 and the Yeates brothers for allowing access to fish 

 catches and for facilitating field sampling. Two anon- 

 ymous reviewers contributed comments that signifi- 

 cantly improved the manuscript. 



Literature cited 



Bannerot, S. P., W. W. Fox Jr., and J. E. Powers. 



1987. Reproductive strategies and tlie management of snap- 

 pers and groupers in the Gulf of Mexico and Caribbean. In 

 Ti'opical snappers and groupers: biology and fisheries man- 



