Influence of marine reserves on reef fish recruitment in the upper Florida Keys

Abstract

Coral reef fish recruitment to the upper Florida Keys was monitored monthly for 7 years (2003–2009) to establish a baseline and test whether recruitment varied between reserve and non-reserve sites. Recruits <30 days old were surveyed in two primary habitat types (reef and rubble) in each of two replicate reserve and non-reserve sites. Recruitment of all fish species peaked in the summer and early fall; winter recruitment was consistently low. Some interannual recruitment patterns were roughly similar among species, with recruitment generally lower in 2004 for several taxa, possibly reflecting a system-wide process. During 7 peak recruitment months each year, overall recruitment to reef habitat was significantly higher in non-reserve sites in 2 of 7 years. In contrast, recruitment to rubble habitat was significantly higher in reserves in 3 of 7 years. Specific fish taxa had variable patterns of recruitment to reserves and non-reserves: Despite high interannual variation in recruitment magnitude, Scaridae (parrotfish) densities were significantly higher in reserves than in non-reserves. Densities of two abundant goby taxa (Gnatholepis thompsoni and Coryphopterus spp.) were also higher in reserves than in non-reserves, but the magnitude varied among years. Recruitment of the bicolor damselfish, Stegastes partitus, did not differ consistently between reserves and non-reserves. Densities of Thalassoma bifasciatum had an opposite trend relative to other taxa, with densities typically higher in non-reserves than in reserves (in 6 of 7 years; significant in only 2 years). Higher recruit densities (scarids, gobies, and all rubble taxa together) within reserves were coupled with significantly lower densities of intermediate-sized piscivores and significantly greater cover of Dictyota spp. macroalgae and turfs relative to non-reserves. Reserves may be areas of relative refuge from predation for some fish recruits due to a combination of reduced predator abundance and enhanced small-scale structural habitat.