Patterns of Fish Abundance Associated with a Dredge Disposal Island: Implications for Fish Habitat Enhancement in a Large Reservoir

Abstract

Abstract We evaluated trends in fish abundance associated with in-water disposal of dredged material in Lower Granite Reservoir, Idaho–Washington. Fish assemblages were sampled before (1985) and after (1993) construction of a 0.37-ha disposal island to assess local changes in fish community structure, In addition, resident fish abundance was monitored for 5 years (1989–1993) near the disposal island and compared with patterns of fish abundance at other shallow-water sampling stations in the reservoir. Ranked abundance of fishes collected in gill-net samples differed before and after construction of the disposal island. Of 12 common resident fishes in Lower Granite Reservoir, only 6 species were represented in gill-net catches before construction of the island, whereas 11 species were represented in catches after construction. Trophic structure and trends in feeding-guild abundance were not significantly different between disposal and reference stations from 1989 to 1993. However, herbivores and insectivor...