Karr's Index of Biotic Integrity (IBI) approach provides a biological measure of ecosystem health using a wide spectrum of metrics which can be extracted from fish catch data obtained using standardized methods. Extensive electrofishing surveys of littoral fish assemblages, conducted in three Great Lakes' Areas of Concern, provided the basis for developing a lacustrine IBI that was 12 metrics of three broad types: (i) species composition, (ii) trophic composition, and (iii) abundance and condition. In contrast with lotic IBIs where diversity and abundance metrics have mostly been used, several biomass metrics were adopted to accommodate the large size range of lentic fishes. The variability of repeated measures was low enough to allow valid testing of intertransect differences with three to five samples per transect. Comparisons among survey areas showed significant differences consistent with the varying levels of ecosystem degradation. Analyses of mean IBI values with measures of submerged vegetation density and cover by transect produced significant positive correlations. This IBI developed for the Great Lakes' littoral zone, both by design and by demonstrated correlations, integrates the effects of four main factors influencing fish assemblages and hence revealing ecosystem health: exotic fishes, water quality, physical habitat supply, and piscivore abundance.

Community fish production data were summarized from the literature to test the hypothesis that production is higher in rivers than in lakes. Average community production at 55 river sites was three times greater (273 kg∙ha−1∙year−1) than at 22 lakes (82 kg∙ha−1∙year−1). Higher production (P) in rivers resulted from much higher densities of fish (14 times) and greater biomass (B) (about 2 times). Average fish weight and P/B ratios were inversely correlated. Average fish weight was 7 times less, and P/B ratios were 1.5 times higher (after correction for fish size), in rivers than in lakes. Thus, rivers not only had higher average biomasses of fish but also the turnover rate of the biomass was greater. Fish production was positively correlated with phosphorus in both lakes and rivers. Information on community fish production supported the hypothesis that the productivity of river habitat is, on average, higher than the productivity of lake habitat. The productive capacity of freshwater habitats can be predicted using a multiple regression model developed by Boudreau and Dickie (Can. J. Fish. Aquat. Sci. 46: 614. 1989), where fish production is calculated from average fish biomass and body mass.

Often the Before-After-Control-Impact (BACI) design is suggested as being a statistically powerful experimental design in environmental impact studies. If the timing and location of the impact are known and adequate pre-data are collected, the BACI design is considered optimal to help isolate the effect of the development from natural variability. This paper presents 9 years of results from a long-term BACI experiment tested using a range of statistical models and post-impact monitoring designs. To explore suboptimal designs that are often utilized in environmental effects monitoring, the same data were also explored assuming either no control system was available (Before-After only), or that no pre-impact data were available (Control-Impact only). The results of the BACI design were robust to the statistical model used, and the BACI design was able to detect effects from the impact that the two suboptimal designs failed to detect. However, the BACI design demonstrated different conclusions depending on the number and configuration of post-impact years included in the analysis. Our results reinforce the idea that caution should be employed when using, or interpreting results from, a BACI design in an environmental impact study, but demonstrate that a well-designed BACI remains one of the best models for environmental effects monitoring programs.

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Hatchery-reared Atlantic salmon (Salmo salar) parr were captured 1–3 mo after release in streams, along with wild parr from the same streams. Identification of their stomach contents showed total number of organisms and number of taxa per stomach were greater and there was a higher index of stomach fullness in wild than in hatchery parr resident ≤ 2 mo in a stream. Wild parr consumed more Brachycentridae, Hydroptilidae, Diptera, and Plecoptera than did hatchery parr, but sometimes less Odontoceridae and Heptageniidae. These differences may have arisen from size-dependent food selection, the effects of feeding experience, or possible microhabitat differences between wild and hatchery parr. Key words: salmon parr, hatchery-reared, wild, feeding