Number of Trout and Sunfish Species

 

This metric was adopted as a hybrid for warmwater and coldwater streams. The metric is

similar to that used in a combined coldwater-warmwater version of an IBI developed in

Ontario (Steedman 1988), but designed for high-gradient rather than low-gradient streams.

Both sunfish and trout are water-column species sensitive to habitat degradation and loss of

instream cover (Gammon et al. 1981; Angermeier 1983). In coldwater streams where sunfish

are typically absent, trout fill a similar ecological niche and may be used to replace sunfish.

Trout are equally, if not more sensitive to habitat degradation. The relationship between trout

populations and habitat is well documented (Peters 1967; Hunt1969; Meehan 1991). Metric

recalibration has resulted in the elimination of green sunfish and bluegill, as these species are

designated as tolerant by the USEPA (Plafkin et al 1989).