Eastern Pacific reef fish responses to coral recovery following El Nino disturbances

This study examined fluctuations in an eastern Pacific reef fish assemblage as it varied with coral recovery over 30 yr. Concurrent fish and coral monitoring were conducted at Uva Island reef, which lies within the boundaries of Coiba National Park, Panama, in an area that has received virtually no fishing pressure or watershed development over the past 80 yr. Coral and fish monitoring spanned the 1982-1983 and 1997-1998 El Nino disturbances-anomalous warming events that selectively killed reef-building corals. While no fish mortalities were observed during the 1982-1983 El Nino event, live coral cover was reduced to nearly 0% at the study reef. From 1984 to 1990, live coral (Pocillopora spp.) cover was extremely low (< 5%), but demonstrated steady recovery to similar to 35% by 2010. By quantifying disturbance-related, long-term changes in coral reef resources and relating these to fish trophic group responses, several functional relationships emerged. A total of 63 fish taxa were observed, and reef fish density (all taxa combined) remained relatively stable. Multivariate analysis of species abundances revealed a strong overlap between seasons and a clustering of community composition in the years following bleaching. Fish species richness increased significantly as live coral cover rose from near 0 to 15-20% and then demonstrated a decreasing trend to 35% cover. Benthic invertivores showed a significant parabolic increase in density peaking at similar to 20% live coral cover. A pattern of decline was apparent for the mixed diet feeders guild as coral cover increased, whereas an asymptotic relationship with coral cover emerged for the facultative corallivore guild. No clear patterns in herbivore, piscivore and planktivore abundance were apparent with increasing coral cover. The varying responses of invertivore, corallivore and mixed diet feeders guilds demonstrated strong associations with coral cover, probably reflecting changes in the availability of their respective trophic resources during reef recovery. Thus, variations in coral cover probably influence fish communities through trophic pathways involving invertebrate food sources.