214 



Fishery Bulletin 98(1) 



Figure 14 



Estimated mean water depth (±SE), based on minimum 

 and maximum depths provided by captains, during fish- 

 ing efforts in the longline and snapper reel fisheries. Data 

 were collected through the Trip Interview Program (TIP) 

 at the South Carolina Department of Natural Resources 

 from vessels landing their catches in South Carolina. 

 Sample sizes ranged from 141 to 851. 



ily exploited and possibly overexploited. A situation 

 of greater concern would be one where size at age 

 has decreased after a sustained high level of fishing- 

 induced mortality, as has been reported for red porgy, 

 Pagrus pagrus, and vermilion snapper, Rhombop- 

 lites aurorubens, in our study region (Harris and 

 McGovern, 1997; Zhao et al., 1997). There is evi- 

 dence that faster-growing individuals in the popula- 

 tions of red porgy and vermilion snapper have been 

 effectively eliminated, thus causing a decrease in 

 size at age. Red porgy exhibited a density-dependent 

 response after an initially high level of fishing mor- 

 tality, but the sustained high level of mortality even- 

 tually removed the faster-growing individuals. Size 

 at age should be monitored to ensure that this does 

 not occur in the snowy grouper population. 



The age composition of the snowy grouper land- 

 ings also needs to be monitored because the long- 

 line fishery is presently supported by younger age 

 classes ( 1-6). The present study showed that snowy 

 grouper can attain an age of 29 yr, but only 19*7^ of 

 the fish caught on longlines were >age 6 (Table 4). 

 The low percentage of older age classes in the land- 

 ings supports the preliminary sex ratio data from 

 the 1990s, showing that the percentage of males had 

 significantly decreased. 



• = Snapper reel 

 o = Longline 



1983 1985 1987 1989 1991 1993 1995 1997 

 Year 



Figure IS 



Mean length (±SE) of snowy grouper landed in North 

 Carolina in the longline and snapper reel fisheries. 

 Data were collected through the Trip Interview Program 

 (TIP) at the North Carolina Department of Health, 

 Environment, and Natural Resources. Sample sizes 

 ranged from 5 to 1908 fish. 



Age and growth 



A comprehensive comparison of growth data in our 

 study with previously published results was not pos- 

 sible because 1) lack of large and old specimens and 

 small sample sizes, and 2) differences in study area 

 (Florida Keys in Moore and Labisky [1984|). One or 

 more of these factors could explain the differences 

 in size at age, k, and L^^ between the results of two 

 published studies (Matheson and Huntsman, 1984; 

 Moore and Labisky, 1984) and our results for long- 

 line and snapper reel data from the 1980s. A primary 

 reason for higher values of L^, in the published stud- 

 ies (Table 3) is that the growth curves do not exhibit 

 asymptotes, which is probably due to low numbers 

 of specimens greater than approximately 900 mm 

 and older than 15-17 yr. In our study, all the data 

 sets (2 bandit reel and 2 longline) had individuals 

 over 1000 mm and at least 21 yr old. Sample sizes in 

 two data sets were very small (<200): our longline or 

 Kali pole data set (;! = 163) and the data set of back 

 calculations (n = 118) in Moore and Labisky (1984). 

 Important factors that could not be evaluated on the 

 basis of previous publications were 1) similarity of 

 fishing gear, 2) method of increment interpretation, 

 and 3) whether or not a weighting factor was used 

 when fitting the von Bertalanffy growth model. 



