Prohibiting spearfishing boosts conservation outcomes for partially protected areas

Abstract

Partially Protected Areas (PPAs) are a ubiquitous management tool, yet their ecological effects are often poorly understood. Here, we compare conservation outcomes for two different kinds of PPAs (allowing limited line fishing, but with or without spearfishing) on sheltered and exposed sides of coral reefs of the southern Great Barrier Reef. Compared with No-Take Marine Reserves (NTMRs), Conservation Park Zones (CPZs; spearfishing allowed), had lower biomass and density of primary fisheries targets. Conversely, Special Management Areas (SMAs; spearfishing prohibited) had similar biomass and density of primary targets to NTMRs, and had greater densities of coral trout (a key fishing target), compared to CPZs. No zoning patterns occurred for non-target species. Both PPA zones supported greater biomass of targets compared to less regulated Habitat Protection Zones, which have more allowable fishing activities. These results indicate that partial protection measures limiting fishing activities can create conservation outcomes for targeted fishes. In particular, we provide evidence to support the premise that prohibition of spearfishing can significantly boost conservation outcomes for PPAs. Zoning outcomes did not differ between exposed and sheltered sides of reefs, despite exposed sites consistently supporting a greater biomass and density of fishes. The success of PPAs, and in particular SMAs, in the region is likely due to a combination of factors including: strong enforcement and subsequent compliance of fishing restrictions, the presence of adjacent effective NTMRs, and a long duration of protection. Our results highlight the valuable contributions that PPAs can make to conservation outcomes in well managed MPAs.