Influence of Aquatic Macrophytes on Age‐0 Largemouth Bass Growth and Diets

Abstract

AbstractMacrophyte removal by lakefront property owners occurs on glacial lakes throughout the range of Largemouth Bass Micropterus salmoides, yet little information exists on how it affects recruitment of these fish populations. We hypothesized that with greater prey availability in macrophytes, age‐0 Largemouth Bass consumption and growth would increase. To test this hypothesis, we conducted an in‐lake experiment with age‐0 Largemouth Bass in twelve 9.29‐m2 littoral mesocosms in glacial Chancellor Lake, Michigan, during summer and fall 2014. We removed macrophytes from mesocosm substrates to produce low‐coverage, high‐coverage, and vegetation edge treatments and determined treatment effects on consumption and growth at differing age‐0 Largemouth Bass stocking densities (0.86–2.15 fish/m2). When macrophytes were present, age‐0 Largemouth Bass stomachs contained fewer zooplankton, contained terrestrial invertebrates more often, and contained aquatic macroinvertebrates less often than when macrophytes were absent. Age‐0 Largemouth Bass consumed more fish prey in macrophyte edge and high macrophyte coverage enclosures stocked at moderate densities, resulting in total stomach content biomass increases that increased growth and, potentially, recruitment. Age‐0 Largemouth Bass from enclosures with macrophyte edge and high macrophyte coverage grew 9.7 ± 2.2% (mean ± SD) and 8.3 ± 1.9% longer, respectively, than their counterparts in low macrophyte coverage enclosures; fish in macrophyte edge or high macrophyte coverage treatments at moderate stocking density gained 109.3 ± 45.1% and 110.7 ± 45.0% more weight, respectively, than those in low‐coverage enclosures. These results demonstrate a causal linkage between macrophytes and age‐0 Largemouth Bass consumption and growth in lakes. We recommend that fisheries managers seeking to increase consumption and growth rates in age‐0 Largemouth Bass consider protecting and restoring macrophytes in littoral habitats up to 60% coverage to potentially decrease mortality and improve recruitment.