Contact with seaweed alters prey selectivity in a coral-feeding reef fish

摘要

Human-driven disturbance is fundamentally altering the composition of benthic marine communities. For instance, many coral reefs are experiencing declining coral cover alongside increased macroalgae (seaweed) abundance. While the responses of herbivorous fishes to sea-weeds are comparatively well understood, little is known regarding the responses of other important trophic guilds that interact with the benthic community, such as corallivores. To this end, we investigated how 2 species of seaweed (Galaxaura filamentosa and Sargassum polycystum) affected foraging in an obligate corallivorous fish, Oxymonacanthus longirostris. Corals with no seaweed contact were preferred over corals in contact with seaweed, regardless of the seaweed species. However, following seaweed removal, fish associated with, and fed on, all corals equally, suggesting that corals in contact with these seaweeds do not produce repellant chemical cues. This second finding contrasts with patterns seen in other corallivores, indicating that, while seaweeds may be generally repellent, sensory cues used to make foraging decisions may vary. Regardless, these findings provide further evidence that seaweeds negatively affect foraging in non-herbivorous fishes, which could have far-reaching impacts as habitat quality declines.