"Once the sewage treatment facility was upgraded and also when the combined flows were eliminated from the Twin Cities area, the water quality started to improve and it took quite a few years for the river to recover.
"We don't have information on the fish population every year during the recovery period but we do have intermittent surveys of the fish population during the recovery time and we did see what I would call the classic response: the water quality improves, the bottom conditions improve, the fish population responds and the structure of the fish population started to revert back to what it would be in a more normal river. In fact, in the area of the pool that used to have the real heavy areas of sludge deposition, zero levels of oxygen and high levels of ammonia, today we see good populations of smallmouth bass, good populations of walleye which would be indicative of much better conditions because their habitat requirements are quite strict, they require high oxygen levels.
"So the fish population started to restructure, got much more like a normal river and the fish population became a real magnet for anglers. Over the last 10-15 years especially, anglers discovered especially the walleye fishing in the pool, and pretty soon we got into a problem with real heavy fishing pressure. The fish population was so high that we were attracting large numbers of anglers. And in fact, we eventually put a special regulation on the pool to protect some of the game species from overexploitation. So it's really an amazing story where you go from where there are very poor populations of game fish to where the fish population becomes so abundant that it attracts large numbers of anglers and we actually had to put regulations in place to try to protect the fish population.
"I think probably the best symptom of the improving conditions was the occurrence of smallmouth bass in the lower part of the pool. To me, as a biologist, it's just amazing to see the smallmouth living where once no fish could live or if there were any fish at all, they were fish like carp or black bullheads."