Fisheries Restrictions and Their Cascading Effects on Herbivore Abundance and Macroalgae Removal at Kenyan Coral Reefs [post]

Ewout Geerten Knoester, Veerle Eline Plug, AJ Murk, Susan Okoth Sande, Ronald Osinga
2022 unpublished
The increase of macroalgae at degraded reefs impedes ecosystem services and calls for effective methods to facilitate a return to coral dominance. Removal of macroalgae (i.e. browsing) is typically realized by fish, but the role and identity of browsers at the heavily-fished East African Coast is still largely unknown. This study investigated how browsing pressure at Kenyan reefs (-4.700, 39.396) related to fisheries management and herbivore abundance. From October 2018 to January 2019,
more » ... ion during 24-h buffet assays using the brown macroalgae Sargassum and Padina was determined and video recorded at six sites: two in fished zones, two in marine reserves (traditional fishing allowed) and two in no-take zones. Herbivorous fish composition and biomass and urchin abundance were also determined. Consumption of both Sargassum and Padina was significantly lower in the fished zones (25% and 27% of macroalgal biomass consumed, respectively) compared to the no-take zones (66% and 81%), with intermediate consumption in the marine reserves (49% and 73%). Biomasses of herbivorous fish (browsers, grazers and scrapers) were between 3 to 30 times higher in the protected zones, whereas sea urchins and territorial damselfish were more abundant in fished zones. Macroalgae consumption correlated positively with the biomass of browsing and grazing fish and negatively with sea urchin abundance. Fish from various functional groups were identified as dominant browsers and these differed strongly across sites. These results indicate that fishing restrictions are likely to support reef resilience by increasing herbivorous fish biomass of key species and thereby promote macroalgae removal.
doi:10.21203/ fatcat:gdbopl3zkrhr3cryqwruafyesm