Daily and monthly ichthyoplankton assemblages of La Azufrada coral reef, Gorgona Island, Eastern Tropical Pacific

The description of the daily and seasonal variation of the species composition and abundance on the early stages of fishes in coral reefs can lead to a better understanding of fish population dynamics in these ecosystems, because settlement and recruitment processes depend on larval fish supply. Daytime and nighttime samples of ichthyoplankton were collected through circular surface tows using a bongo net between October 2010 and November 2011 at La Azufrada, the largest coral reef on the Colombian Pacific coast, located in Gorgona Island. A total of 2,171 fish larvae representing 87 species in 42 families were identified. The most important species by their frequency of occurrence and density were Anisotremus sp., Cetengraulis mysticetus, Bregmaceros bathymaster, and Gobiidae sp.4. Daytime and nighttime samples showed variations in the composition of the assemblage, with a greater number of species at night, evidencing short-scale variations over a diel cycle. On the other hand, environmental parameters such as oxygen, salinity, pH, temperature, and zooplankton biomass were also measured; however, none of them had a strong relationship with the larvae assemblage structure throughout the year. In conclusion, this study suggests that night conditions had a higher effect over the ichthyoplanktonic species found in La Azufrada coral reef than the observed changes in the environmental parameters.