Brian W. Nagy and Doran M. Mason, Department of Forestry and Natural Resources, Purdue University, 1159 Forestry Building, West Lafayette, Indiana 47907-1159; Voice 765-494-2379 FAX 765-496-2422 E-Mail bnagy@fnr.purdue.edu, doran@fnr.purdue.edu

Pelagic planktivorous fishes aggregate at artificial reef structures and are known to be an important food resource for some species of piscivorous reef fishes. However, despite their importance little is know about the distribution and persistence of pelagic fishes at artificial reefs. The objective of this study was to collect preliminary data on the distribution of pelagic planktivorous fish and their association and persistence with reefs. We measured the diel distribution, density, and size-structure of fish using a BioSonics 120kHz DT6000 digital hydroacoustic system. Pelagic fish were sampled at two different spatial scales: at a large scale (km) to determine the association of pelagic fishes to reef structures and at a fine scale (m) to determine their persistence on the reefs. Initial analysis indicates that fish appear to have higher densities over the reefs when compared to the surrounding area. Fine scale sampling illustrates a dispersion and reaggregation process occurring from night to day, respectively. Reasons for the increased density and congregation on the reefs have not been determined, but two possible explanations are the reefs provide a common location for fish to find one another, and/or the reefs provide food due to upwelling of benthic organisms around the reefs.