Habitat Suitability Index for Largemouth Bass in Tidal Rivers of the Chesapeake Bay Watershed

Abstract

AbstractThe largemouth bass Micropterus salmoides is arguably the most sought fish species by inland anglers in North America. The suitability of inland habitats for supporting largemouth bass populations can differ remarkably but is difficult to quantify. I developed and evaluated the utility of a habitat suitability index (HSI) for largemouth bass in tidal freshwater portions of selected drainages in the Chesapeake Bay. The HSI comprised suitability scores ranging from 0 (not suitable) to 1 (perfectly suitable) and was calculated from seven separate suitability models in which suitability scores were functions of summer water temperature (°C), summer dissolved oxygen (mg/L), summer pH, maximum monthly salinity (‰), submerged aquatic vegetation coverage (%), monthly average water clarity, and stream discharge (m3/s) during the spawning season. Some of the suitability models that contributed to the HSI were modified to reflect species–habitat relationships observed for largemouth bass in drainages of the Chesapeake Bay from 2003 to 2008. Based on the HSI, drainages ranged from moderately suitable (HSI = 0.57) to highly suitable (HSI = 0.84). Spatial and monthly differences in HSI were positively correlated with relative abundance of largemouth bass; similar habitat conditions among years led to low interannual variation in HSI, which was not correlated with annual differences in relative abundance. Although the HSI may be useful in summarizing habitat suitability for a species, it may obscure important physical and biotic interactions that could affect the species’ distribution.