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

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 two-year period, assessing a)
the change in adult and juvenile L. trabeculata density
within harvested and non-harvested (control) plots (~90m2), b) the impact
of L. trabeculata harvesting on reef fish and
macroinvertebrate assemblages, and c) the change in density of the most
abundant L. trabeculata-associated species. The experiment was
conducted over a two-year period, from December 2016 to May 2019.
Approximately 90% of L. trabeculata was removed by an
experienced kelp fisherman in experimental plots. After two
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 non-harvested 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 re-establish 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.