Chapter 17 - Reef Fish Ecology and Grouper Conservation and Management

Abstract

This chapter evaluates the degree to which basic reef fish ecology can help reef fish managers by reviewing key aspects of the life history of groupers. Ranging in size from 25 cm to over 3 m, groupers occur mostly in shallow water, with a few species occurring in depths as great as 300 m. They are important components of most reef fish fisheries, and are highly esteemed as food fishes that are very susceptible to nearly every type of fishing gear, a combination that is typically catastrophic for fish populations. In many cases, protection for grouper stocks is inadequate or nonexistent, and given their high value, rapid overfishing of groupers is common. As with most reef fishes, attempts at stock assessments and management of groupers are relatively recent, and data shortages hamper the ability to make informed management decisions. Numerous groupers travel to specific locations to form spawning aggregations and tend to spawn in early spring and summer, with a general trend toward later spawning with increasing latitude. Spawning activity in groupers is often correlated with lunar or semilunar rhythms and the groupers are usually considered to be protogynous hermaphrodites. Although primary males may occur in some species, juvenile groupers typically mature and function as females. Males are produced when adult females change sex. Thus, sex ratios tend to be female biased, although there is a great variation both among and within species. Simulated effects of protogyny on yield-per-recruit, stock biomass-per-recruit (SSBR), and other measures of reproductive capability suggest that protogynous species lose reproductive capacity more rapidly with increasing fishing and sustain reproductive failure at lower levels of fishing, as compared to gonochoristic species. Compensation through conservation of the numerical sex ratio, and through conservation of the cohort male biomass:fecundity ratio, result in reduced and eliminated effects of protogyny, respectively.