Current Marine Protected Areas Conserve Fish Spawning Aggregations Under Climate Change due to Habitat Refugia

In addition to overfishing threats, tropical reef fishes that form spawning aggregations are threatened by climate change, which can reduce management effectiveness. While management strategies such as marine protected areas (MPAs), seasonal sales bans, and seasonal fishing closures may be effective at reducing the impacts of fishing pressure, they may not be as effective in the future as climate change reduces suitable fish habitat. By examining oceanographic conditions at known spawning sites of critically endangered Nassau grouper (Epinephelus striatus), along with future climate conditions under multiple emissions scenarios (RCPs 4.5 and 8.5), projections were made of suitable spawning habitat throughout the species' range. Spawning habitat in no-take MPAs and protected under seasonal sales bans and fishing closures was compared to spawning habitat in unprotected regions and times of year to determine potential success in protecting Nassau grouper spawning under current and future conditions. By the end of the century, declines in suitable spawning habitat were projected throughout the region under both climate scenarios. Most countries showed declines in effectively protecting spawning habitat, but MPAs had 31% higher spawning suitability than surrounding areas due to the presence of refugia with persistently suitable temperatures at the end of the century. By the end of the century, only modest improvements (≤ 10%) could be made by locating new MPAs to maximize protection of spawning sites. Additionally, spawning phenology shifts on average by 25 days under RCP 8.5, which can be mitigated in countries with seasonal bans by adjusting closures to match this change. Creating networks of smaller MPAs can maximize conservation of spawning habitat because they can incorporate climate refugia, are easier to enforce, and would protect a variety of habitats.