Does Herbivorous Fish Protection Really Improve Coral Reef Resilience? A Case Study from New Caledonia (South Pacific)

Abstract

Parts of coral reefs from New Caledonia (South Pacific) were registered at the UNESCO World Heritage list in 2008. Management strategies aiming at preserving the exceptional ecological value of these reefs in the context of climate change are currently being considered. This study evaluates the appropriateness of an exclusive fishing ban of herbivorous fish as a strategy to enhance coral reef resilience to hurricanes and bleaching in the UNESCO-registered areas of New Caledonia. A two-phase approach was developed: 1) coral, macroalgal, and herbivorous fish communities were examined in four biotopes from 14 reefs submitted to different fishing pressures in New Caledonia, and 2) results from these analyses were challenged in the context of a global synthesis of the relationship between herbivorous fish protection, coral recovery and relative macroalgal development after hurricanes and bleaching. Analyses of New Caledonia data indicated that 1) current fishing pressure only slightly affected herbivorous fish communities in the country, and 2) coral and macroalgal covers remained unrelated, and macroalgal cover was not related to the biomass, density or diversity of macroalgae feeders, whatever the biotope or level of fishing pressure considered. At a global scale, we found no relationship between reef protection status, coral recovery and relative macroalgal development after major climatic events. These results suggest that an exclusive protection of herbivorous fish in New Caledonia is unlikely to improve coral reef resilience to large-scale climatic disturbances, especially in the lightly fished UNESCO-registered areas. More efforts towards the survey and regulation of major chronic stress factors such as mining are rather recommended. In the most heavily fished areas of the country, carnivorous fish and large targeted herbivores may however be monitored as part of a precautionary approach.

A test of trophic cascade theory: fish and benthic assemblages across a predator density gradient on coral reefs

“…Taylor 2014;Williams et al 2015a) in highly dynamic ecosystems such as coral reefs before attributing differences in fish density and biomass to fishing effects alone. Similar to predator-herbivore interactions, we found no significant cascading trophic links between the density of herbivorous fishes and benthic composition (also see Carassou et al 2013). However, we found some regional differences in benthic composition, with CCA on average five times as abundant in the Ribbons, and rubble and sand on average nearly five times as abundant in the Swains.…”

Spatial distribution of surgeonfish and parrotfish in the north sector of the Mesoamerican Barrier Reef System

“…However, the high macroalgae on all habitats in this study did not significantly affect the abundance and biomass of herbivorous fish as suggested by the RDA. Similar results have been found in other studies (Wellington & Victor 1985;Williams 1986;Chabanet & Letourneur 1995;Carassou et al 2013). For example, Abah was dominant on the fronts, where despite the overwhelming dominance of macroalgae, it did not significantly influence the abundance and biomass distribution of this or any other species.…”

“…Similar results have been found in other studies (Wellington & Victor ; Williams ; Chabanet & Letourneur ; Carassou et al . ). For example, Abah was dominant on the fronts, where despite the overwhelming dominance of macroalgae, it did not significantly influence the abundance and biomass distribution of this or any other species.…”

Similar impacts of fishing and environmental stress on calcifying organisms in Indian Ocean coral reefs

“…The one weak association was a negative association between acan thurids and coral cover that would indicate their preference for feeding on dead coral surfaces (Marshell & Mumby 2012). While this does not support some ecosystem management recommendations, it does correspond with a number of large-scale studies that have failed to find significant coral− parrot fish associations, identified other factors, or found that herbivorous fish passively associate with, rather than actively control, algae-coral relationships (McClanahan et al 2011b, Wilson et al 2012, Carassou et al 2013, Russ et al 2015, Suchley et al 2016.…”