A process for developing and evaluating indices of fish assemblage integrity

Abstract

We describe a general process for developing an index of fish assemblage integrity, using the Willamette Valley of Oregon, U.S.A., as an example. Such an index is useful for assessing the effects of humans on entire fish assemblages, and the general process can be applied to any biological assemblage and any region. First, a reference condition was determined from historical information, and then candidate metrics of ecological importance were listed. The variability of the candidate metrics in time and space was estimated and their responsiveness to independent measures of riparian and stream habitat quality assessed. Metrics were scored continuously from 0 to 10, producing an index of biological integrity (IBI) that was weighted to range from 0 to 100 regardless of the number of metrics. The index, developed from a set of 35 sites, was then tested on an independent set of eight urban sites sampled by the Oregon Department of Fish and Wildlife. Thirteen of the 16 candidate metrics were appropriate and produced an IBI with among-site variance triple that of revisit variance. The method distinguished sites with acceptable fish assemblages from marginally and severely impaired sites.

A Preliminary Fishery Quality Index for Portuguese Streams

“…Likely, reduced within-site variability of species metrics (noise), increased among-site variability (signal), or both provided stronger correlations between predictor variables and FQIs than for SQIs. Hughes et al (1998) and Mebane et al (2003) reported that their IBIs had greater among-site versus within-site variability (signal/noise) than the metrics forming them. But Hughes et al (2004) and Whittier et al (Lyons et al 1996;Mundahl and Simon 1999;Ferreira et al 2007;Whittier et al 2007).…”

“…Also, Hickman (2000) proposed a sportfishing [Article] index for reservoir populations, but his index uses rank scores of 5, 10, or 15 for each of four qualitative population characteristics (angler quantity and quality, population quantity and quality), while each of the five components of the population quality characteristic was scored 1, 2, or 3. Such scoring increases the variance of indices as compared with continuous metric and index scoring (Hughes et al 1998;Pont et al 2006).…”

Monitoring Methods Based on Fish

“…by Suter, 1993), although strong counter arguments have been also presented by others (e.g. Simon and Lyons, 1995;Karr and Chu, 1997;Hughes et al, 1998).…”

“…Therefore, it is of paramount importance to rely on the widest base of testers and collaborators when developing a multimetric index. Even when a multimetric index has been correctly developed (see, for instance, Hughes et al, 1998), its ability to measure environmental perturbations depends on the right combination of metrics that are taken into account. Of course, there are no general rules that can help in selecting proper metrics, but usually the latter are chosen on the basis of their presumed general ecological relevance or because of their responsiveness to specific perturbations (e.g.…”

A zone-specific fish-based biotic index as a management tool for the Zeeschelde estuary (Belgium)

“…This visual analysis allowed the first selection of appropriate metrics for each zone, i.e., those metrics that separate different pressure classes. Out of these relevant metrics we indicated those with a high contribution to the variation (F1 or F2 > ±0.55) using a principal component analysis (PCA) with the log transformed metric values (log(x + 1)) (Hughes et al, 1998). From these we tested for redundant metrics by a Pearson correlation (McCormick et al, 2001: r > 0.75, p < 0.05).…”