Effects of Zebra Mussel (Dreissena polymorpha) on the Feeding Ecology of Early-Stage Striped Bass

Invasion of zebra mussel in the Hudson River sharply reduced phytoplankton biomass and markedly altered estuarine energy flow. Previous studies suggest that early-stage fishes of several species were negatively impacted by the invasion, including the Striped Bass. While abundance, growth, and distribution of Striped Bass are well documented throughout the zebra mussel invasion, diet and feeding success have been unanalyzed. The objective of this study is to analyze feeding success, physiological condition, gut fullness, and diet composition of bass over multiple years, including pre-invasion and post mussel invasion years. We hypothesized that feeding success and condition would decrease in mussel impacted years and that diet would shift towards a more littoral based diet rather than pelagic. Analysis to test this hypothesis is possible thanks to 21 years of early-stage fish samples collected as part of the Hudson River Utilities’ long-term monitoring program. We found that condition of bass varied among years, such that condition was relatively high in some pre-invasion years and relatively low in some post-invasion years. Diet composition did not differ between years nor were there clear shifts in littoral or pelagic prey prevalence. We are currently conducting multivariate analyses of gut fullness and diet composition