Development of Habitat Suitability Indices for the Candy Darter, with Cross‐Scale Validation across Representative Populations

Abstract

Understanding relationships between habitat associations for individuals and habitat factors that limit populations is a primary challenge for managers of stream fishes. Although habitat use by individuals can provide insight into the adaptive significance of selected microhabitats, not all habitat parameters will be significant at the population level, particularly when distributional patterns partially result from habitat degradation. We used underwater observation to quantify microhabitat selection by an imperiled stream fish, the Candy Darter Etheostoma osburni, in two streams with robust populations. We developed multiple‐variable and multiple‐life‐stage habitat suitability indices (HSIs) from microhabitat selection patterns and used them to assess the suitability of available habitat in streams where Candy Darter populations were extirpated, localized, or robust. Next, we used a comparative framework to examine relationships among (1) habitat availability across streams, (2) projected habitat suitability of each stream, and (3) a rank for the likely long‐term viability (robustness) of the population inhabiting each stream. Habitat selection was characterized by ontogenetic shifts from the low‐velocity, slightly embedded areas used by age‐0 Candy Darters to the swift, shallow areas with little fine sediment and complex substrate, which were used by adults. Overall, HSIs were strongly correlated with population rank. However, we observed weak or inverse relationships between predicted individual habitat suitability and population robustness for multiple life stages and variables. The results demonstrated that microhabitat selection by individuals does not always reflect population robustness, particularly when based on a single life stage or season, which highlights the risk of generalizing habitat selection that is observed during nonstressful periods or for noncritical resources. These findings suggest that stream fish managers may need to be cautious when implementing conservation measures based solely on observations of habitat selection by individuals and that detailed study at the individual and population levels may be necessary to identify habitat that limits populations. Received March 30, 2016; accepted July 19, 2016Published online October 7, 2016

Evaluation of Potential Translocation Sites for an Imperiled Cyprinid, the Hornyhead Chub

“…). We calculated a NMDS ordination for all habitat variables using two dimensions and a Euclidean distance matrix because habitat variables were normalized using log( x + 1) transformation (Dunn and Angermeier ). We calculated stress values to assess how well NMDS configurations preserved the original dissimilarity distances.…”

Remaining populations of an upland stream fish persist in refugia defined by habitat features at multiple scales

“…We surveyed 42 segments during May–July, 2012. We limited surveys to riffles, where E. osburni spends most of its life (Dunn & Angermeier, ). Within each segment, we randomly selected three geographical coordinates within 300 m of a road or trail and sampled the closest riffle to each coordinate twice to limit imperfect detection (i.e., three riffles per segment).…”

Characterizing species co‐occurrence patterns of imperfectly detected stream fishes to inform species reintroduction efforts

“…Instead, the best available information is typically limited to comparisons of current ecological conditions with other regions where the species exists, allowing investigators the ability to infer factors associated with species viability. Fish habitat‐suitability models provide a valuable tool for identifying suitable reintroduction locations (e.g., Dixon & Vokoun ; Dunn & Angermeier ). For example, Dunn and Angermeier () sampled 4 streams in West Virginia and Virginia (U.S.A.) that contained robust, localized, or extirpated populations of the imperiled candy darter ( Etheostoma osburni ), and built habitat‐suitability models to better understand variation in microhabitat use, which could ultimately inform future reintroduction efforts of the species.…”