Studies on Damselfish (Pomacentridae) Larvae from the Island of Oahu, Hawaii

Ichthyoplankton sampling was conducted at three power plants on the island of Oahu in Hawaii from April 2006–April 2010. All of the sampling was completed in front of the plant intakes along the shoreline, but covered a range of habitats including the open coast on the west side of the island near Kahe Point, and inside both Pearl and Honolulu Harbors. Damselfish (Pomacentrid) larvae was the most abundant taxonomic group collected during all four years at the Kahe and Honolulu locations making them the second most abundant larvae collected from all three plants combined. The size of most of the damselfish larvae were close to the reported hatch sizes for the most common species in this family. The small size of most of the larvae made them impossible to visually identify to species, and as a result our taxonomic separation was limited to the family level. Additional funding from the Electric Power Research Institute (EPRI) through the Hawaiian Electric Company allowed us to submit a sample of these larvae for DNA analysis. Although there are 17 species of damselfishes found in Hawaiian waters, the DNA results showed that the collected larvae included seven species with the Hawaiian sergeant, Abudefduf abdominalis, being the most abundant. This species along with two other species of sergeants comprised over 91 percent of the damselfish larvae analyzed. As a result, we were able to limit our research on life history parameters necessary for adult equivalent modeling to these closely related species. It also provided insights into our field data such as the sharp decline we observed in the number of larvae older than 3-4 days when the yolk sac is absorbed and the larvae must begin feeding. The observed peaks in abundance generally coincided with published records of the reproductive cycle of Hawaiian sergeants. These insights plus other published information were used to develop a set of parameters for estimating the adult equivalents from the larvae entrained by the plants.