Population dynamics of smallmouth bass in response to habitat supply

Abstract

We have developed an age-structured, spatially explicit model to estimate smallmouth bass ( Micropterus dolomieu) population dynamics from the readily available habitat data of a lake. Habitat suitability models were used to rank the suitability of different sites throughout a lake for smallmouth bass. Population dynamics were then linked to the habitat suitabilities via a home range mechanism, a density-dependent mechanism and the ideal-free distribution theory. The home ranges are calculated as a function of size, the density-dependent mechanism assumes that habitat suitability will decrease as the density of fish at a site increases and the ideal-free distribution theory assumes fish will seek out more suitable habitats. When all fish are distributed throughout the lake, growth is calculated as a function of temperature and density. This consequently affects the fecundity of the mature females, survival of the young-of-year (YOY) and the number of fish recruited to the population in subsequent years. Sensitivity analyses indicated that the habitat alterations that increased YOY survival (increased temperature and total nesting habitat) had the greatest impact on population dynamics and suggests that conservation or restoration efforts should focus on the nesting (YOY) habitat. When validated, the model described the population indicators, total number of nests and fish, better than the spatial distribution of fish within the study lakes. These findings suggest that in its current state, the model may be successfully used to guide smallmouth bass population and habitat management practices. Future developments of the model are also discussed.