For coastal communities around the world, coral reefs are not just beautiful underwater locations. In areas with few alternative resources, these unique ecosystems provide small-scale fisheries and the populations they support with access to a diverse range of species for commercial harvest.

But beyond their economic significance, reef fish play a crucial role in keeping local communities healthy. In the Seychelles obesity and cardiovascular disease are key health concerns, along with high levels of anaemia, low birth weights and stunted growth. These conditions are associated with a lack of specific micronutrients, which the consumption of fish that inhabit coral reefs can help reduce.

However, climate change has begun to have harmful impacts on reef communities, with coral bleaching one of the most visible effects. As sea temperatures rise, corals expel algae from within their tissues causing the coral to turn white and the two major bleaching events in the Seychelles in 1998 and 2016 dramatically transformed local habitats. Although some reefs recovered, many transformed into ecosystems dominated not by coral but by seaweed or rubble.

A recent study led by Dr Sarah Martin and colleagues from the Lancaster Environment Centre examined how these changes have affected the reefs and the populations that rely on them. Her research categorised reefs into four recovery types based on these changes: coral-dominated, rocky, mixed, and macroalgal-dominated.

Each habitat was different, changing the number and types of fish available to catch and sell. Coral-dominated reefs support the highest diversity of fish species and yield larger quantities of fish, yet more fish are harvested from macroalgal-dominated reefs which have lower species diversity. Rocky and mixed reefs occupy a middle ground between the extremes. The diverse fishes associated with coral habitats, including snappers and groupers, command a wider range of market values, while macroalgal habitats favour herbivorous species like rabbitfish, which are commonly caught, particularly as these habitats become more widespread. These changes also influence the nutritional value of fish, and while all habitats supported nutritious fish, coral-associated fish were richer in omega-3 fatty acids and vitamin A, and macroalgal-associated fish were higher in iron and zinc.

These changing ecosystems mean that local fishers must adapt to the new environment. Confronted with the threat of more frequent and sustained bleaching events, combined with increasing effort and declining catch rates, managing tropical reef fisheries sustainably is ever more important. Strategies that focus on rebuilding stocks of diverse, coral-associated reef species are vital. and may be possible without adversely affecting nutritious food supplies by maintaining fisher access to species associated with other reef habitats.

Although coral reefs may never return to their pre-bleaching states, they can still support livelihoods and nutrition if managed wisely. For coastal communities in the Seychelles and beyond, this balance will be critical in navigating an uncertain ocean future.

The full research paper can be found here.