Impacts of Introduced Blueback Herring on Piscivorous Sportfish in a Southeastern U.S. Reservoir

Non-native species have sometimes been introduced to increase forage availability and sportfish production, but such introductions have potential for negative as well as positive effects. In 2010, non-native blueback herring (Alosa aestivalis) were found in Lewis Smith Lake, Alabama, due to illegal stocking. Our objective was to quantify food habits and determine potential impacts of blueback herring introduction on body condition and growth of important sportfishes in Lewis Smith Lake. Largemouth bass (Micropterus salmoides), Alabama bass (Micropterus henshalli), and striped bass (Morone saxatilis) were sampled in 2013 and 2014, and diets of these post-blueback herring introduction piscivores were quantified. Relative weight and length-at-age data from these fish were combined with data from Alabama Department of Conservation and Natural Resources and Auburn University collected prior to blueback herring introduction to quantify any changes in relative weights or length at age. Overall, piscivore diets included blueback herring at lower percentages (4.5, 19.5, and 6.6% for largemouth bass, Alabama bass, and striped bass, respectively) than other fish prey (52.2%, 58.7%, and 92.2% for largemouth bass, Alabama bass, and striped bass, respectively). Only summer striped bass diets contained high proportions of blueback herring. Relative weights of all sizes of largemouth bass and Alabama bass and intermediate sized striped bass were significantly higher after blueback herring introduction. This increased condition did not result in increased mean-length-at-age for piscivores age-4 and younger (except age-1 and age-2 striped bass). Blueback herring contributed to piscivore diets and increased body condition of some piscivores, with little change observed in growth. However, long-term effects should be assessed as blueback herring densities increase in the reservoir.