Growth, pH Tolerance, Survival, and Diet of Introduced Northern-Strain and Native Southern-Strain Appalachian Brook Trout

Abstract

The native range of brook trout Salvelinus fontinalis in southern Appalachia has been drastically reduced by human activities over the last century. Restoration of brook trout populations was attempted through stocking of hatchery-reared fish that were derived from populations native to northern Appalachia; these northern brook trout are genetically distinct from populations native to southern Appalachia. The extent of ecological differences between the naturalized, hatchery-derived northern brook trout (NBKT) and native southern brook trout (SBKT) is unknown but may have important implications for southern Appalachian stream ecosystems. We used a combination of laboratory, outdoor raceway, and natural stream experiments to test for differences in growth, pH tolerance, survival, and diet between introduced NBKT and native SBKT. Fish were collected separately for each experiment from wild allopatric populations in North Carolina. Northern brook trout had higher average survival than SBKT in the laboratory and raceway experiments, although the difference was significant only in the laboratory experiment. Northern brook trout had higher growth rates in the laboratory regardless of pH treatment, but growth was similar between strains in the raceway experiment. Relative condition factor was reduced by low pH, regardless of strain. Diets differed between the two strains in the natural stream experiment; NBKT consumed a larger percentage of terrestrial insects than did SBKT. These data offer the first experimental evidence of genetically based ecological differences between pure strains of wild, hatchery-derived NBKT and native SBKT in southern Appalachia.

Received December 8, 2009; accepted October 6, 2010

ACKNOWLEDGMENTS

We thank B. Salter, W. Haney, and M. Lavoie for field and laboratory assistance and the Biology Department at Western Carolina University for logistical support. Partial funding was provided by the Mountain Aquaculture Research Center, Cullowhee. Comments from the associate editor and two anonymous reviewers greatly improved the manuscript.