Ocean surgeonfish Acanthurus bahianus. II. Fishing effects on longevity, size and abundance?

Abstract

The ocean surgeonfish Acanthurus bahianus, an abundant small herbivore on reefs throughout the tropical west and central Atlantic, is a significant component of Caribbean trap-fishery catches. To assess effects of fishing on this species we compared its longevity, survivorship, size and abundance at localities throughout its range that have differing intensities and targets of fishing. Temperature explains nearly all of the geographic variation in maximum longevity of A. bahianus, and most of the variation in adult survivorship, with no indications of consistent fishing effects on either. Variation in maximum and median length (1.6-fold) and in abundance (16-fold) also are not consistently related to fishing. A. bahianus has similar demographic characteristics at 2 neighbouring (50 km apart) offshore Venezuelan reefs, one a well protected reserve, the other with intense fishing for predators. At Panamá, the abundance of adult A. bahianus showed no trend of change from 1979 to 1997, as the local density of subsistence fishers increased by ~70%. The lack of consistent fishing-effects on this species found in this and some other studies may reflect a combination of (1) resilience to fishing mortality arising from rapid growth to asymptotic size, early maturity, small size and abundance, and (2) strong, natural, large- and small-scale spatial variation in demography and abundance obscuring any such effects. Effects of non-catastrophic fishing on sedentary reef-fishes with similar demographic characteristics probably will be revealed only through comparisons of subpopulations in adjacent fished and no-take areas involving careful consideration of small-scale habitat effects.