A. I'm sure there are places where hatchery effluents can degrade water quality downstream, but I would also guess that problems are largely site specific depending on the characteristics of the effluent and the receiving stream. One of the ongoing plans to enhance anadromous salmonid returns to the Yakima River system in WA was to add a series of rearing ponds in the drainage to supplement natural reproduction. I was asked to determine if the effluents would have any effect on the primary production (algal growth and oxygen production) in the receiving streams. I examined this by determining how much nitrogen and phosphorus would be added from each pond, whether this would change the existing ratio of nitrogen and phosphorus in the stream, and predicting whether the change in the nutrient regime would be significantly enough to enhance algal production. In no case did the added effluents change the nutrient regime significantly. Now, this is just one situation that I was involved with, and I was not concerned with benthic fauna. I'm not sure whether this was published by the state or not; I retired and left the lab and have lost track of what happened to the report. I could find out if you want me to pursue it; contact me at cecushing@aol.com.