A Review of the Potential Effects of Coal Bed Natural Gas Development Activities on Fish Assemblages of the Powder River Geologic Basin

Coal bed natural gas (CBNG) development in the Powder River geologic basin (PRGB) may alter water quality, quantity, or aquatic habitats. CBNG product water is generally higher than surface waters in dissolved sodium and bicarbonate and sometimes exceeds toxicity levels for fathead minnows and daphnids. Montana and Wyoming water quality standards do not account for differential ion toxicity; toxicity data for most fishes of the PRGB are lacking, and there are minimal data available on composition of CBNG product water. One field study suggests that CBNG may limit fish distribution. Metals and trace elements in CBNG product water, wetlands, impoundments, sediments, and biological tissues may exceed chronic standards or other biologically relevant thresholds. Product-water dissolved oxygen, pH, and turbidity are comparable to surface waters, but spatiotemporal temperature variation may disrupt natural cues. Increased discharge from CBNG product-water discharge or groundwater depletion may alter the ecology of PRGB streams. Indirect effects may occur if development alters food webs, plant communities, or aquatic habitats. Road construction may increase sedimentation, and stream crossings may fragment fish populations. Impoundments may be a source of non-native fish species. The uncertainty concerning potential effects of CBNG development on fish in the PRGB highlights the need for further research and monitoring.