Evaluation of a Modified Habitat Suitability Index Model for Eastern Brook Trout: Implications for Efficient Habitat Assessment

Abstract

Species-specific habitat suitability models have potential for use in restoration efforts, but their efficiency still remains in question. As eastern brook trout, Salvelinus fontinalis, populations in New England have declined over the last few decades as a result of anthropogenic and natural impacts on critical habitat, habitat suitability models have become a common tool for conservation efforts. These models, however, have inherent flaws that prevent widespread and uniform use. To better adapt these models, the flaws must be properly addressed. Using a modified habitat suitability index (HSI) model developed for eastern brook trout, we explained the correlation between catch per unit effort (CPUE) of brook trout with designated HSI variables such as temperature, dominant substrate type, and percent riffle fines for nineteen reaches within the Westfield River watershed. CPUE was not significantly correlated with HSI outputs. A principal components analysis (PCA) was employed and revealed driving factors within the system. Four variables were shown to yield the highest explained variance over the first two axes: velocity, instream cover, percent pools, and thalweg depth. Evidence suggests that habitat assessment based around these core variables may lead to a more efficient and accurate assessment. Recommendations for improved methodologies include revised tolerance curves, a reworked index rating system, and revised model variables based on current field research. Alterations to existing models provide hope for more accurate assessment, and increased efficiency in conservation efforts.