Small-scale spatial variation in the population structure of vermilion snapper (Rhomboplites aurorubens) from the northeast Gulf of Mexico

This study estimated the variation in demographic parameters in vermilion snapper, Rhomboplites aurorubens, on a small spatial scale (i.e., tens of kilometres). Vermilion snapper were collected from seven reef sites in the northeastern Gulf of Mexico using hook and line. Sagittal otoliths were collected from vermilion snapper sampled over a 2 years period. Vermilion snapper were assigned ages from 1 to 14 years and were assumed to be fully recruited to the sampling gear by age 4 or 5 at most reef sites. Significant differences were noted in mean total length and age by reef site, depth zone and distance from shore. The overall sex ratio of vermilion snapper favored females (1.6:1) with no significant difference in this ratio for fish collected during spawning months versus non-spawning months, depth zone or distance from shore; however, there were significant differences in sex ratios by site. Differences were noted in growth by reef site, depth zone and distance from shore using size at age and in reef site using otoliths weight at age. A middle depth site consistently indicated faster growth than all other sites. Von Bertalanffy growth curves for males and females were different, however the growth coefficient (k) was not. Mortality rates did not differ by site, depth zone or distance from shore. The results of this study underscore the importance of spatial scale for understanding the dynamics of reef fish populations.