Hood and Johnson; Life history of Rhomboplites aurorubens 



835 



Discussion 



Collections 



The vermilion snapper that we sampled from 

 the eastern GOM were smaller than those col- 

 lected during the 1980s from the western 

 GOM. Most hook-and-line-caught fish that we 

 sampled (88%) were between 201 and 325 mm 

 TL and were smaller than fish collected from 

 the Texas Flower Gardens by Zastrow (1984) 

 and Nelson ( 1988). The fish they sampled were 

 mostly (757f ) between 269 and 474 mm TL and 

 262 and 517 mm TL, respectively. Gear bias 

 is probably not responsible for the differences 

 in length distributions. As in our study, both 

 Zastrow (1984) and Nelson (1988) examined 

 fish caught principally with hook-and-line 

 gear. Furthermore, Nelson (1988) examined 

 the length distributions of vermilion snapper 

 caught with different hook sizes (Mustad no. 

 2-no. 4/0) and noted no differences in the size 

 offish caught. 



Other factors, such as depth and movement, 

 probably cannot explain the differences be- 

 tween the size distribution of fish caught in 

 our study and that offish caught in the west- 

 ern GOM. Nelson ( 1988) caught most vermil- 

 ion snapper from depths between 60 and 90 m. 

 We do not know the depth at which the fish 

 we sampled were captured; however, the mean 

 depth at which vermilion snapper were caught by 

 the eastern GOM commercial fishery in 1995 was 

 80 m ( Schirripa'' ) and is within the depth range given 

 by Nelson (1988). The presence of larger fish in the 

 western GOM could be the result of larger fish mov- 

 ing from the eastern to western GOM. However, this 

 movement seems unlikely because tagging data sug- 

 gest that vermilion snapper are residents of reefs and 

 do not travel long distances (Beaumariage, 1964; 

 Fable, 1980; Grimes et al., 1982). 



Increases in fishing pressure may have reduced 

 the average size of fish caught by the fishery. 

 Schirripa^ reported that the average size of fish in 

 the GOM commercial fishery dropped from a high of 

 371 mm TL in 1984 to a low of 320 mm TL in 1993. 

 Over this same time, commercial landings increased 

 from 1.6 million pounds in 1984 to 2.5 million pounds 

 in 1993, and recreational landings increased from 

 0.2 million fish in 1984 to 1.2 million fish in 1993. 



The sex ratio of GOM vermilion snapper is differ- 

 ent from the sex ratio reported for snapper from the 

 SAB. In the GOM, female-to-male sex ratios were 

 not significantly different from 1:1 (Zastrow, 1984; 

 Collins'^; this study), or they significantly favored 



18 25 18 39 31 14 31 82 60 42 34 21 



S 20 - 



Female 



I I Immature 



^^ Resting 

 ^^ Early 



developing 



lllllll Developing 



I I Ripe 



Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 



IVIale 



NWWi Resting 



YX/vxA Developing 



1=1 Ripe 



illli n Spent 



Oct Nov Dec Jan Feb Mar Apr May Jun Jut Aug Sep 



Month 



Figure 6 



Percentage of vermilion snapper from the eastern Gulf of Mexico 

 in gonad development classes by month and by sex. 



males (1:1.2; Nelson, 1988). In the SAB, females sig- 

 nificantly outnumbered males, and sex ratios ranged 

 from 1.6:1 to 1.7:1 (Grimes and Huntsman, 1980; 

 Cuellaretal., 1997; Zhao and McGovern, 1997). Zhao 

 and McGovern ( 1997 ) partitioned sex ratios from the 

 SAB by depth, fish size, sampling year, gear type, and 

 latitude. Of these, only gear type and latitude signifi- 

 cantly affected the sex ratio. Females were proportion- 

 ally more common in trap and hook-and-line collections 

 than in trawl collections. Although Zhao and McGovern 

 ( 1997 ) were cautious about attributing decreases in the 

 proportion of females to changes in latitude, 1:1 sex 

 ratios reported in the GOM (Zastrow, 1984; Collins^; 

 our study) and from Puerto Rico ( Boardman and Weiler, 

 1979) are consistent with this hypothesis. We did not 

 find any significant differences in sex ratios by season; 

 however, Zastrow (1984) and Nelson (1988) reported 

 an increase in the proportion of males in the summer 

 in the western GOM. 



Age and growth 



Sectioned otoliths can be used to age eastern GOM 

 vermilion snapper and produce higher readability 



