Evaluating the Potential Impacts of the Introduced Blueback Herring, Alosa aestivalis, on the Aquatic Communities in Lewis Smith Lake, Alabama

Abstract

Reservoir food webs are complex, making prediction of the influence of introducing new species difficult. Blueback Herring Alosa aestivalis were first discovered in Lewis Smith Lake, Alabama in 2010 and both positive and negative effects are likely to be expressed depending on the species and life stage being affected. Responses elsewhere in the Southeastern U.S. have demonstrated that Blueback Herring can compete with other fishes for zooplankton at multiple life stages. Alternately, introductions might increase prey availability for piscivores and increase piscivore growth and condition. I sampled all life stages of Blueback Herring and resident sport fishes in Lewis Smith Lake over 2 years (2013-2014). High diet overlap between juvenile and adult Blueback Herring and both larval Lepomis spp. and adult Threadfin Shad Dorosoma petenense for zooplankton prey suggests a potential for competition across multiple life stages. When comparing pre-Blueback Herring data with post-Blueback Herring data, I found significant increases in relative weights of adult Alabama Bass Micropterus henshalli and Largemouth Bass Micropterus salmoides, and Striped Bass Morone saxatilis. Clearly resident fishes will experience a complex mix of positive and negative responses to Blueback Herring introductions, and the overall effect will be some combination of these. Additional research is required to fully quantify these effects and potential effects.