Effects of harvesting on subtidal kelp forests (Lessonia trabeculata) in central Chile

Abstract

The systematic degradation of marine ecosystems is a global phenomenon that has important and diverse consequences including biodiversity loss and reduced ecosystem service provisions. In temperate regions, subtidal kelp forests are dominant ecosystems in rocky coasts, subjected to the influence of local-scale stressors and regional environmental variation. For example, kelps within the Humboldt Current System are at risk of degradation from live-harvesting by fisheries. However, limited information exists regarding the long-term consequences of kelp harvesting, which, in turn, limits the ability to provide effective management and conservation efforts. Here, we examined the ecosystem-level consequences of the artisanal subtidal Lessonia trabeculata fishery along the coast of central Chile during a 2-year period, assessing (1) the change in adult and juvenile L. trabeculata density within harvested and nonharvested (control) plots (~90 m2), (2) the impact of L. trabeculata harvesting on reef fish and macroinvertebrate assemblages, and (3) the change in density of the most abundant L. trabeculata-associated species. The experiment was conducted over a 2-year period, from December 2016 to May 2019. Approximately 90% of L. trabeculata was removed by an experienced kelp fisherman in experimental plots. After 2 years, L. trabeculata and its associated community showed a lack of recovery in the harvested plots. Within these plots, the average abundance of the rock shrimp, Rhynchocinetes typus, and the herbivorous snail, Tegula tridentata, was greater than in nonharvested plots and the pattern persisted over the study period. The difference in abundance of associated species may be key to the (lack of) recovery of L. trabeculata forests. Our study highlights the impact of L. trabeculata harvesting on associated fauna; however, significant knowledge gaps remain regarding the capacity and time frame to reestablish the original biomass of L. trabeculata, as well as its associated fauna. The management of L. trabeculata fisheries needs to account for ecosystem-wide impacts in order to better manage and protect vital coastal ecosystems.