Habitat Suitability Modeling to Evaluate Conservation and Enhancement Efforts for Gulf-Strain Striped Bass in Mississippi Coastal Rivers

Abstract

Conservation of native populations such as Gulf-strain striped bass Morone saxatilis is a priority for preserving historic fisheries and maintaining biodiversity. Habitat alteration is thought to be the primary driver of native striped bass decline in Mississippi coastal rivers, so it is a priority to understand current habitat suitability as part of a comprehensive restoration plan. A bioenergetics model is a useful tool to examine habitat suitability by using growth rate potential as an indicator of habitat quality. The purpose of this study was to develop a habitat suitability model for Gulf-strain striped bass that incorporates seasonal and spatial variability in temperature, salinity, and dissolved oxygen in an index river system along the Gulf of Mexico coast, Mississippi. Environmental data collected with a stratified-random survey during fall, winter, spring, and summer of 2008–2009 were incorporated into a spatially explicit bioenergetics model. Model-predicted growth rates were analyzed by season and salinity zone in a geographical information system framework. Model results suggested that growth rate patterns significantly differed spatially and between summer and the other seasons. Habitat suitability is greatly reduced during summer and concentrated in specific parts of the river system, suggesting the existence of habitat hot spots that are potentially important to population viability. Gulf-strain striped bass appear to be nonmigratory; therefore, high summer temperatures in the river system make upper thermal tolerance the most important factor limiting summer distributions and growth of these fish. Additional laboratory studies on Gulf-strain striped bass’ environmental tolerances and habitat use are needed. Nonetheless, this study demonstrates the value of habitat suitability assessment as a tool for fish conservation planning.

Received May 4, 2011; accepted December 19, 2011

ACKNOWLEDGMENTS

We thank Larry Nicholson and Jimmy Christmas for their advice and support based on their 40 years of experience with striped bass stock enhancement; we also thank Mark Peterson and Eric Hoffmayer for their assistance in planning the study. The extensive habitat survey could not have been completed without the work contributed by the many field assistants; Rebecca Haehn, Jennifer McKinney, and Nicole Shaffer primarily assisted in the field. This work was funded by the Coastal Impacts Assessment Program of the Mississippi Department of Marine Resources and by the U.S. Fish and Wildlife Service.