Fish Are Providing Life-Saving Services to Corals—And Scientists Are Just Beginning to Understand How

Our review reveals that on coral reefs, the relationship between fish and their coral hosts runs deeper than simple shelter-seeking. We synthesized decades of research on coral-fish relationships to reveal patterns that individual experiments might miss, focusing on species that maintain close spatial relationships with live coral structures—from obligate coral dwellers like damselfishes and gobies to facultative species like grunts and snappers.

The numbers tell a compelling story. We found that grunt schools foraging away from reefs at night but sheltering near corals during the day increase nitrogen and phosphorus concentrations around their host corals by tenfold. This nutrient boost leads to 75% increases in growth of Acropora cervicornis. In another study spanning 13 months, corals hosting resident damselfish showed approximately 37% greater growth in skeletal surface area compared to fishless corals. We also documented how damselfish swimming movements increase coral photosynthesis by 3-6% during daylight hours by enhancing water flow.

Our findings show these relationships are highly context-dependent. In areas with high nitrogen concentrations and high flow, the positive relationship between fish density and coral growth actually reverses. Beneficial effects observed in small-scale studies don't always scale up to reef-wide surveys, suggesting complex interactions between fish services and environmental conditions.

"These findings matter because coral reefs face unprecedented threats from climate change, pollution, and overfishing."

These findings matter because coral reefs face unprecedented threats from climate change, pollution, and overfishing. Understanding fish-coral partnerships could help enhance restoration efforts. If fish truly buffer corals against environmental stressors, protecting these partnerships becomes as important as protecting the corals themselves.

The future of coral restoration may depend not just on replanting corals, but on ensuring the right fish communities are there to support them.

Citation

Stier, Adrian C.; Chase, Tory J.; Osenberg, Craig W. (2025). Fish services to corals: a review of how coral-associated fishes benefit corals. Coral Reefs.

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