Comparing responses in the performance of sentinel populations of stoneflies (Plecoptera) and slimy sculpin (Cottus cognatus) exposed to enriching effluents
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Programs in Canada that assess the effects of wastewater discharges on organisms, such as Environmental Effects Monitoring (EEM), primarily focus on fish populations and benthic invertebrate communities. Although these methods are widely accepted, there are many situations where fish monitoring is difficult and benthic community data is difficult to interpret; in these instances alternative approaches should be used. There are, however, few alternative methods available. One potential alternative is to use invertebrate population endpoints to determine effects in the receiving environment. In this study we examined effects of sewage and pulp mill effluents in the Saint John River, New Brunswick, on two stonefly genera (Plecoptera, Perlidae, Acroneuria spp. and Paragnetina spp.) and compared the responses to those of a small-bodied fish, the slimy sculpin (Cottus cognatus). Stonefly measurements included condition, developmental stage, gonad weight, and size upstream and downstream of sewage and a pulp mill discharge. Condition, developmental stage, and absolute gonad weight were greater in Paragnetina spp. downstream of the sewage discharge. Acroneuria spp. showed persistence of the late developmental stage downstream of the sewage inputs. Slimy sculpin exposed to sewage effluents also showed increased condition, but the impacts downstream of the pulp mill effluent were inconsistent in both sculpin and Paragnetina spp. Our findings suggest that stonefly populations and slimy sculpin respond to effluents in similar ways and that the responses of large long-lived invertebrate populations, such as stoneflies, may be a viable alternative to fish population monitoring in environmental assessments of point source discharges.
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