Zhao and McGovern: Variation in sexual maturity and sex ratio of Rhomboplites aurorubens 
847 
and hook-and-line were similar to each other (traps: 
72.1%; hook-and-line: 68.0%) but differed from that 
for trawl capture (59.9%). Trawls caught smaller fish 
from shallower waters when compared with traps 
and hook-and-line (Tables 2 and 7C). However, 
present results indicated that sex ratios were not 
affected by water depth or fish length. With traps 
and hook-and-line gear, baits were used to attract 
fish. If female vermilion snapper were more aggres- 
sive in pursuing bait than males, the percentage of 
females in the catch of traps and hook-and-line could 
be higher than that in the population. In contrast, 
no baits were used for trawling, and therefore males 
and females might be caught with the same prob- 
ability. If the difference in feeding behavior between 
sexes can account for the difference in sex ratio be- 
tween gear, then the sex ratio of vermilion snapper 
in the population may be correctly represented by 
the trawl catch. Watanuki et al. ( 1993) reported that 
basket traps caught the greatest ratio of female 
cuttlefish among three types of gear (basket traps, 
jigs, and trammel nets). More females may be at- 
tracted to traps for spawning, but Watanuki et al. 
indicated that there are probably other unknown 
factors governing the entry of cuttlefish into traps. 
Because information on spawning behavior of ver- 
milion snapper is unavailable, we cannot evaluate 
how the spawning activity of vermilion snapper may 
affect its vulnerability to different gear types. 
We pooled data from all gear types and calculated 
the overall sex ratio by period. The percentage of fe- 
males gradually increased from 62% in 1979-81 to 
70% in 1991-93. The temporal increase in the per- 
centage of females proved to be an artifact of unequal 
distribution of catch by gear among periods. Reasons 
for the difference in sex ratios among gear types are 
unknown. Caution must be used when evaluating the 
sex ratios of any fish species collected by various gear 
types. 
Our conclusion of independence between sex ra- 
tios and lengths differs from previous studies. Grimes 
and Huntsman (1980) concluded that the sex ratio 
of vermilion snapper was dependent on fish length, 
with the percentage of females increasing in larger 
size classes. However, the percentage of females 
within the range of 551-600 mm TL (89.3%, n= 32) 
was obviously higher than those for other length 
ranges. Thus, it is suspected that the significant chi- 
square calculated by Grimes and Huntsman (1980) 
was probably due to this length range. We used the 
original data published in Table 4 of Grimes and 
Huntsman (1980) but excluded the data with length 
greater than 550 mm TL (n= 32). We found that sex 
ratio was independent of length (x 2 =13.105, P=0.108, 
n=841, df=8, TL=101-55Q mm) and thus was in 
agreement with the conclusion of the present study. 
A further 2x2 contingency table analysis formed by 
the TL range of 551-600 mm versus all other length 
ranges rejected the null hypothesis of independence 
between sex ratio and length (% 2 =11.732, P=0.001, 
n= 873, df=l). Thus, we confirmed that the sex ratio 
within 551-600 mm TL is significantly different from 
those of other length ranges. Because our data had 
relatively few vermilion snapper larger than 450 mm 
TL, the conclusion of independence between sex ra- 
tio and length may be limited to 450 mm TL or less. 
However, the similar size-at-age and the same lon- 
gevity of male and female vermilion snapper do not 
suggest the percentage of females would increase 
with length even beyond 450 mm TL (Zhao et al., 
1997). 
Acknowledgments 
We thank W. A. Roumillat and D. M. Wyanski for 
their advice and help with data analysis. We are 
grateful to the many individuals who participated 
in the field effort and to W. A. Roumillat, G. R. 
Sedberry, D. S. Vaughan, and to two anonymous re- 
viewers for helpful comments on an earlier draft of 
this paper. This research was supported by the Na- 
tional Marine Fisheries Service, MARMAP contract 
Number 50WCNF006002, and the South Carolina 
Department of Natural Resources. 
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