Ecosystem health in coastal areas targeted by small-scale artisanal fisheries: Insights on monitoring and assessment

摘要

The assessment of the status of marine ecosystems is still a major challenge, because in general we lack well established ecosystem-based monitoring programs. The coast of central Chile is subjected to moderate but historic fishing pressure by small-scale fisheries. In spite of the increasing evidences of the impact of fishing. beyond target species, there is a lack of systematic ecosystem-based assessments. We focused on this problem with the goal of identifying community components, based on a Biological Traits Analysis, that respond to fishing activities to ultimately define ecosystem health. We sampled a set of study sites subjected to benthic invertebrate gathering, and more recently to kelp harvesting. Sites included paired fishery restricted and open access areas where mobile invertebrates and sessile benthos were surveyed. In addition, kelp density and size structure were assessed in two sites subjected to kelp harvesting (also pairing restricted and open access areas). Target species exhibited higher densities in fishery-restricted areas. Fisheries restricted-areas also showed overall higher richness and redundancy of biological traits. Otherwise, we observed high variability in the structure of sessile benthos linked to small-scale heterogeneity of the seabed. The areas subjected to kelp harvesting exhibited variability in mobile invertebrates' composition between fishing access regimes, whereas no effects could be detected by only considering target species. Current monitoring efforts seem to be well-suited to address target species but fail to inform on ecosystem health in an area with increasing signs of community-wide effects from fishing. Therefore, we recommend future monitoring schemes targeting community components, beyond commercial species' densities, at different scales.