Trophic restructuring of coral reef fish communities in a large marine reserve

Abstract

Marine reserves can directly replenish heavily fished species. However, communitywide effects of reserves are less clear. Marine reserves directly reduce fishing mortality rates, but through the restoration of apex predators, reserves may have strong indirect effects on non-target species. We explored the effects of a large, fully protected marine reserve in the Bahamas on the community of coral-reef fishes. We examined the effect of the reserve on fish biomass by comparing the density and size of all fishes on similar reefs located inside and outside the reserve. Total biomass of fishes was approximately 7× higher in reserve sites, where biomass was strongly concentrated in species of higher trophic levels. Analysis based on the relative magnitude of individual species' responses indicated that, on average, the largest species increased in biomass within the reserve, intermediate-sized species decreased, and the smallest species exhibited variable responses. Species' responses to the reserve were also examined by pooling species into 9 trophic categories using consumptive relationships, which provided corroborating results. Large piscivores (e.g. sharks, large groupers) were on average larger and more abundant inside the reserve. Mid-trophic-level groups (e.g. small piscivores) had higher average biomass outside of the reserve, where the number of species and biomass of large predators was lower. Finally, some low-trophic-level groups (e.g. planktivores) had higher biomass within the reserve, while others (e.g. small herbivores) did not respond strongly. Overall, these results suggest that marine reserves can substantially alter the composition and structure of reef fish communities. KEY WORDS:Top-down effects · Indirect effects · Food web · Community structure · Coral reef fishes · Fish biomass · Reef-fish communities · Marine reserve Resale or republication not permitted without written consent of the publisher

Pre-existing spatial patterns in fish abundances influence species-specific responses in a Caribbean marine reserve

“…Predatory fish species have shown consistent and positive responses to reserve protection in studies of reserves in the Mediterranean Sea (Guidetti & Sala 2007) and the Red Sea (Ashworth & Ormond 2005). This pattern has also been documented in coral reef systems (Lamb & Johnson 2010). Increased abundance of fishes of higher trophic levels is one possible explanation for the observed decreases in abundance of non-fished species in our study.…”

Highly localized replenishment of coral reef fish populations near nursery habitats

“…Several of the species we examined have important ecological roles either as predators (snappers Lutjanus spp.) that structure local food webs (Stallings 2009, Lamb & Johnson 2010, as grazers (parrotfishes Scarus spp.) that keep fleshy reef algae in a cropped state (Mumby et al 2006, Harborne et al 2016, or as prey (grunts Haemulon spp.)…”

The Role of Pre-Existing Disturbances in the Effect of Marine Reserves on Coastal Ecosystems: A Modelling Approach

“…[49]; [50], [51], [52], [53] in finding clear benefits of reserves to top predators, such as sharks and rays, and those benefits extended well beyond the reserve boundaries. Given the identified critical role of top predators in maintaining the structure and function of ecosystems e.g.…”