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Varying responses of herbivorous and invertebrate-feeding fishes to macroalgal reduction on a coral reef

Lookup NU author(s): Dr Tim McClanahan, Vicki Hendrick, Professor Nick Polunin

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Abstract

The consequences of macroalgal overgrowth on reef fishes and means to reverse this condition have been little explored. An experimental reduction of macroalgae was conducted at a site in the Watamu Marine National Park in Kenya, where a documented increase in macroalgal cover has occurred over the last nine years. In four experimental 10 m by 10 m plots, macroalgae were greatly reduced (fleshy algal cover reduced by 84%) by scrubbing and shearing, while four similar plots acted as controls. The numerical abundance in all fish groups except wrasses and macroalgal-feeding parrotfishes (species in the genera Calotomus and Leptoscarus) increased in experimental algal reduction plots. Algal (Sargassum) and seagrass (Thalassia) assays, susceptible to scraping and excavating parrotfishes, were bitten more frequently in the algal reduction plots one month after the manipulation. Further, surgeonfish (Acanthurus leucosternon and A. nigrofuscus) foraging intensity increased in these algal reduction plots. The abundance of triggerfishes increased significantly in experimental plots relative to control plots, but densities remained low, and an index of sea urchin predation using tethered juvenile and adult Echinometra mathaei showed no differences between treatments following macroalgal reduction. Dominance of reefs by macrofleshy algae appears to reduce the abundance of fishes, mostly herbivores and their rates of herbivory, but also other groups such as predators of invertebrates (triggerfishes, butterflyfishes and angelfishes).


Publication metadata

Author(s): McClanahan TR, Hendrick V, Rodrigues MJ, Polunin NVC

Publication type: Article

Publication status: Published

Journal: Coral Reefs

Year: 1999

Volume: 18

Issue: 3

Pages: 195-203

Print publication date: 23/09/1999

ISSN (print): 0722-4028

ISSN (electronic): 1432-0975

Publisher: Springer

URL: http://dx.doi.org/10.1007/s003380050181

DOI: 10.1007/s003380050181


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