Multi-Scale Spatial Habitat Influences on Largemouth Bass Abundance and Growth

Due to the fact that fish-habitat relationships are often scale dependent there is a need to investigate multi-scale fish-habitat relationships for important sportfish species such as largemouth bass (Micropterus salmoides). In this study, we used regression tree analysis to examine relationships between largemouth bass populations and habitat at four spatial scales across 25 lakes in the central U.S. Landscape regression tree models incorporating major river basins, lake order, and longitude explained 52% of the variation in largemouth bass abundance. At the watershed and riparian scale percent forest cover and percent forest cover and wetland area explained 29% and 51% of the variation in abundance. At the in-lake scale largemouth bass abundance was driven by submerged aquatic vegetation coverage and gizzard shad (Dorosoma cepedianum) abundance explaining 41% of the variation. Size specific growth rates of 300mm largemouth bass were density dependent showing relationships to habitat opposite those of abundance. At the in-lake scale largemouth bass abundance was the only significant variable explaining 20% of the variation in growth. Our results suggest that largemouth bass abundance in the region is driven by landscape and land use effects on macrophytes and gizzard shad whereas growth rates are density dependent.