Journal of Experimental Marine Biology and Ecology Ž . 262 2001 133–153 www.elsevier.nlrlocaterjembe Echinoid bioerosion and herbivory on Kenyan coral reefs: the role of protection from fishing M. Carreiro-Silva a, ) , T.R. McClanahan b a School of Ocean Sciences, UniÕersity of Wales, LL59 5HD Menai Bridge, UK b The Wildlife ConserÕation Society, P.O. Box 99470, Mombasa, Kenya Received 1 March 2000; received in revised form 9 April 2001; accepted 20 April 2001 Abstract During feeding, echinoids remove a large proportion of calcium carbonate in addition to the algae growing on dead coral and are consequently of importance in estimating the turnover of organic and inorganic carbon in coral reefs. Rates of herbivory and the erosion of dead coral substratum, referred to as bioerosion, by the most abundant echinoid species in Kenyan reefs, Ž . Ž . Ž . Echinothrix diadema Linnaeus , Diadema setosum Leske , D. saÕignyi Michelin and Echi- Ž . nometra mathaei de Blainville , were compared in three different reef categories with different Ž. histories of fishing and its exclusion. These were reefs: i protected within Marine National Parks, Ž. which exclude all forms of fishing, coral and shell collection for more than 25 years; ii one reef Ž within a Marine Park, which has received protection from fishing activities for 8 years referred to . Ž . as ‘newly protected’ reef ; and iii unprotected reefs, which experience heavy fishing and some coral collection. The aim was to investigate the grazing and bioerosion activity by the above echinoid species in these reef categories. We surveyed sea urchin population densities and determined their rates of bioerosion and herbivory per individual and square meter. Individual rates of bioerosion and herbivory, of the species D. setosum, D. saÕignyi and E. diadema were estimated from laboratory gut content analysis and gut evacuation experiments in the field, using elevated underwater cages. Individual rates of bioerosion and herbivory of E. mathaei were w Ž . x obtained from a previous field study J. Exp. Mar. Biol. Ecol. 147 1991 121 . Sea urchin bioerosion was greater than herbivory for all studied species and proportional to the body size of the sea urchin species. The large-bodied E. diadema exhibited the highest bioerosion and Ž y1 y1 . herbivory rates 5.5 "0.9 and 2.2 "0.3 g individual day , respectively followed by D. Ž y1 y1 . Ž setosum 1.8 "0.3 and 1.1 "0.2 g individual day and D. saÕignyi 0.7 "0.2 and 0.4 "0.1 y1 y1 . Ž g individual day . Highest sea urchin densities were recorded at unprotected reefs 6.2 "1.5 ) Corresponding author. Present address: Chesapeake Biological Laboratory, Center for Environmental Science, University of Maryland, Solomons, MD 20688-0038, USA. Tel.: q 1-301-405-6938; fax: q 1-301- 314-4139. Ž . E-mail address: mcsilva@wam.umd.edu M. Carreiro-Silva . 0022-0981r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0022-0981 01 00288-X