This is the third compilation of imperiled (i.e., endangered, threatened, vulnerable) plus extinct freshwater and diadromous fishes of North America prepared by the American Fisheries Society'S Endangered Species Committee. Since the last revision in 1989, imperilment of inland fishes has increased substantially. This list includes 700 extant taxa representing 133 genera and 36 families, a 92% increase over the 364 listed in 1989. The increase reflects the addition of distinct populations, previously non‐imperiled fishes, and recently described or discovered taxa. Approximately 39% of described fish species of the continent are imperiled. There are 230 vulnerable, 190 thretened, and 280 endangered extant taxa, and 61 taxa presumed extinct or extirpated from nature. Of those that were imperiled in 1989, most (89%) are the same or worse in conservation status; only 6% have improved in status, and 5% were delisted for various reasons. Habitat degradation and nonindigenous species are the main threats to at‐risk fishes, many of which are restricted to small ranges. Documenting the diversity and status of rare fishes is a critical step in identifying and implementing appropriate actions necessary for their protection and management.

Periphyton assemblage data collected from 233 stream site-visits (49 in 1993, 56 in 1994, and 128 in 1995) throughout the Mid-Appalachian region were used to develop a periphyton index of biotic integrity (PIBI) based on 1) algal genera richness; 2) the relative abundances of diatoms, Cyanobacteria, dominant diatom genus, acidophilic diatoms, eutraphentic diatoms, and motile diatoms; 3) chlorophyll and biomass (ash-free dry mass) standing crops; and 4) alkaline phosphatase activity. Thirty-seven diatom genera and 38 non-diatom genera were collected. The relative richness and relative abundance (RA) of these genera were used to calculate the RA metrics of the PIBI. PIBI scores ranged from 48.0 to 85.1 among the 233 site-visits with an overall regional mean (Ϯ1 SE) of 66.1 Ϯ 0.5. The 10 metrics and the PIBI were correlated with 27 chemical, 12 physical habitat, and 3 landscape variables. Overall, PIBI was inversely correlated with stream depth, stream water color, and Fe. Component metrics were significantly correlated with several chemical (Al, acid neutralizing capacity, Cl, Fe, Mn, N, Na, P, pH, Si, SO 4 , total suspended solids), physical habitat (channel embeddedness, riparian disturbances, stream depth, stream width, substrate composition), and landscape (% of the watershed in forest, agriculture, and urban land uses) variables. Canonical correlation analysis revealed significant correlations between the 10 PIBI metrics and 4 significant environmental gradients related to general human disturbances (stream acidity, stream substrate composition, and stream and riparian habitat). Analysis of variance revealed significant differences in PIBI scores for lowland vs highland streams, and among stream orders. Annual differences were explained by differences in the proportions of sampling sites in lowland streams in each year. The univariate distribution of PIBI scores was used to set threshold PIBI values for the assessment of ecological condition in Mid-Appalachian streams.

From 1993 to 1996, fish assemblage data were collected from 309 wadeable streams in the U.S. Mid‐Atlantic Highlands region as part of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program. Stream sites were selected with a probabilistic sampling design that allowed regional estimates of stream condition. We examined responses of 58 fish assemblage metrics to physical, chemical, and landscape indicators of disturbance. Univariate and multivariate analyses of relationships among fish metrics, habitat integrity, and anthropogenic disturbance were used to develop a fish index of biotic integrity (IBI) for assessing stream condition in the entire region. Of 58 candidate metrics 9 were selected and scored continuously from 0 to 10; the resulting IBI was scaled so that it ranged from 0 to 100. Regional estimates of stream conditions showed that 27% of the stream length in the Mid‐Atlantic Highlands had fish assemblages in good or excellent ecological condition. Of the total wadeable perennial stream length in the region 38% was fair and 14% was poor. There were insufficient data to calculate IBIs for 21% of the wadeable stream length in the Mid‐Atlantic Highlands; all of these streams were small (watershed area ≤2 km2) and lacked sufficient sample size (<10 individuals) to calculate an IBI.

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We tested the ability of delta15N-derived trophic position (TP) to predict polychlorinated biphenyl (PCB) concentrations in a historically contaminated stream (Twelvemile Creek, SC). We analyzed sediment, four types of organic matter, 27 macroinvertebrate taxa, and 25 fish species from six sites spanning 25 stream km. SigmaPCBs were high across sites (mean fish = 2505 ng g(-1) wet), with little spatial variation in concentrations within a trophic level. SigmaPCBs (wet weight) were significantly positively correlated with TP (r2 = 0.56) and lipids (r2 = 0.44), and concentrations increased 1-2 orders of magnitude among trophic levels. After adjusting for lipids, we calculated a food web magnification factor of 1.6 for SigmaPCBs, which is low compared to marine and lentic food webs. The predictive power of TP for individual congeners increased with Kow (octanol-water partition coefficient), with regression slope approximately 0.48 and r2 approximately 0.70 for Kow > 6.5. The proportion of high Kow compounds increased with distance from the source and with trophic position. Spatial variation in congener patterns was high, in contrast to marine and lentic systems where variation is typically low.