Ecological risk and the exploitation of herbivorous reef fish across Micronesia

Abstract

Nominally herbivorous fish play a variety of functional roles that are important in maintaining coral reef resilience, yet are major targets of spear fisheries in Micronesia. Although protection is afforded to iconic species in some areas, impacts of the fishery on the ecosystem are poorly understood. The goal of this study was to locate the major potential ecological threats from the fishery by integrating catch data with species-specific metrics of ecological importance and vulnerability to fishing. Region-wide and country-specific grounds for ecological concern were identified. The heavy exploitation of Naso unicornis was the most serious regional concern-not only was it the most vulnerable species involved in the fishery, but it plays a low-redundancy functional role (i.e. macroalgal browsing) in the ecosystem. The parrotfishes Cetoscarus bicolor, Scarus rubroviolaceus and Chlorurus microrhinos were also implicated in ecological risks (most noticeable in Palau), and the large proportion of immature catch aggravated the concerns found in Pohnpei. An interview-based assessment of species desirability among fishers highlighted the challenges managers may meet locally in diverting attention away from heavily harvested species. Opportunities to alleviate the ecological risks posed by a significant sector of the Micronesian fisheries were identified. Inducing changes in fishers' targeting behaviour towards opportunis - tically-caught species may prove feasible in most countries, and if enacted, may reduce fishing pressure in low-redundancy functional roles. The effectiveness of the policy options supported by the present approach in sustaining reef function and resilience has yet to be assessed. However, we anticipate that informing fishers about the implications of their selectivity may achieve tangible progress in conservation of the species. Therefore, policies which moderate catch rates of highly desirable species, as well as efforts to promote more conscious targeting behaviours, may complement the benefits of the existing networks of marine protected areas. © Inter-Research 2013.