Effects of habitat quality and fishing on Caribbean spotted spiny lobster populations

1. Overfishing has had detrimental impacts on many marine populations. However, measurements of the effect of exploitation are often confounded by intersite differences in habitat quality. 2. To assess the effects of fishing and habitat quality on spotted spiny lobster Panulirus guttatus, the target of a luxury fishery in the Caribbean, lobster populations were assessed on 12 reefs around Anguilla, British West Indies. Habitat quality was measured by the availability of foraging habitat. Fishing intensity was estimated through interviews with fishers. 3. Spotted spiny lobster densities were significantly higher on reefs with good-quality habitat than on poorer-quality reefs. However, mean lobster size remained constant regardless of habitat quality. 4. In contrast, lobsters were on average smaller in heavily fished than in unfished areas because of the removal of the largest size classes by fishers. Changes in densities as a result of fishing could not be detected, and there was no interaction between fishing pressure and habitat quality. 5. The lack of an observable effect of fishing on lobster population densities may be because fishers more intensively target high-quality habitats. Fishing has probably reduced lobster densities on high-quality reefs to a greater extent than on low-quality reefs, but the high productivity of good-quality sites is still sustaining more intense fishing. 6. Synthesis and applications. The importance of habitat quality in sustaining P. guttatus populations in the face of intense exploitation suggests that management efforts should be aimed at enhancing reef health. The latter may be achieved through the establishment of no-take areas on good-quality reefs. Such actions should, however, be expected to generate conflicts with stakeholders because these reefs are currently those most heavily exploited.