732 



Fishery Bulletin 98(4) 



30 



20 



10 - 



October 

 n=14 



30 



20 - 



10 - 



TR RT DP RP SP 



December 

 n=11 



J 



1 — I 

 TR RTDPRPSP 



30 



20 - 



10 



30 



20 



January 

 n=27 



10 - 



TR RT DP RP SP 



February 

 n=17 



I I TT I I 

 TR RTDP RPSP 



30 



20 - 



10 



Marcti 

 n=10 



TR RT DP RP SP 



30 



20 



10 



30 

 20 - 

 10 







50 

 40 

 30-: 



20 -i 



10 

 



April 

 n=16 



TR RT DP RP SP 



1 1 



TR RTDPRP SP 



30 



20 - 



10 



30 



20 - 



10 



30 



20 - 



10 



July 

 n=33 



mI 



TR RT DPRP SP 



August 

 n=46 



1 1 



TR RT DP RP SP 



September 

 n=30 



TR RT DPRP SP 



Male developmental class 



Figure 6 



Frequency of occurrence of male developmental classes by month for red porgy from the eastern Gulf of Mexico. 

 TR = transitional, RT = resting, DP = developing, RP = ripe, SP=spent 



may have had a limited effect on size differences because 

 the mean lengths at age of fish we sampled that were 

 caught with commercial or recreational gear were not sig- 

 nificantly different, and Nelson (1988) reported that the 

 hook sizes did not seem to affect the size distributions of 

 several fish species captured in his study. Finally, biases 

 usually associated with aging structures occur at older 

 ages when rings crowd together at the scale edge and are 

 harder to interpret. Manooch and Huntsman (1977) were 

 able to use scales to age red porgy to 15 years, a much 

 greater age than the maximum age of 6 years reported 

 by Nelson (1988). Therefore, Nelson's estimated ages may 

 accurately describe the ages of the fish he sampled. 



Changes in the average length at age between the early 

 1980s and present may also be the result of size-selective 

 fishing over time, i.e. if larger fish were more vulnerable 

 to capture, then faster-growing fish within an age class 

 would be selectively removed from the population and the 

 result would be a reduced mean size at age for older age 

 classes and an underestimated L (Ricker, 1969; Pitcher 

 and Hart, 1982). We could not demonstrate size-selective 

 fishing pressure, but there was a shift in the size struc- 

 ture of red porgj' stocks in the GOM towards smaller fish 

 (Goodyear and Thompson') — a shift that suggests that 

 fishing pressure is affecting the size structure of the stock. 



For SAB red porgy stocks, Harris and McGovern (1997) 

 have suggested that size-selective fishing and increases in 

 fishing mortality have caused a decrease in mean lengths 

 at age and L^ in SAB red porgy stocks. The average 

 lengths at age 6 years decreased from 451 mm in 1972-74 

 (Manooch and Huntsman, 1977) to 363 mm^ in 1991-94 

 (Harris and McGovern. 1997), and estimated L decreased 

 from 763 mm and 528 mm'' for 1972-74 (Manooch and 

 Huntsman, 1977; Harris and McGovern, 1997) to 412 mm» 

 for 1991-94 (Harris and McGovern, 1997). Although dif- 

 ferences in sampling source (fishery dependent vs. fishery 

 independent) between Manooch and Huntsman ( 1977) and 

 Harris and McGovern ( 1997 ) may have accounted for the 

 observed differences, Harris and McGovern (1997) noted 

 that the same changes occurred from 1979 to 1994 in their 

 fishery-independent samples. Similar trends have been 

 reported for vermilion snapper iRhomhoplites ai/roriibens) 

 in the GOM (Hood and Johnson, 1999) and in the SAB 

 (Zhao et al., 1997), which are a part of the same fishery 

 as red porgy. However, for the SAB, Potts et al. ( 1998) sug- 

 gested that differences in gear types may have accounted 

 for differences in length at age reported by Zhao et al. 

 (1997). 



Red porgy were fully recruited into the GOM recre- 

 ational and commercial fisheries by age 4. This is the same 



