This is a repost from 2013 with updates.
Around 2006 the dam at Taylor’s Falls on the St. Croix had dramatically changed its flow patterns. It used to fluctuate the water levels for developing peak power out of the hydro-dam. Now the flow is what NPS calls “natural run of the river” constant(slower) with no peaking. I believe it was done to help preserve the endangered mussels. Unfortunately it has had some rather huge consequences. Beavers now dam across backwaters and seal off backwater lakes closing them to the main river. These areas were the nursery of the lower St. Croix.
When peaking of the Hydro-dam was fluctuating water levels up to 3 feet daily the beavers could not get dams established. The peaking water would also flush and oxygenate the waters allowing the fish and mussel nurseries to thrive.
Old time fisherman that have been fishing the river for a decade or longer know how much the St Croix has changed over the last >10 years. Most river fish species have been in dramatic decline while lake fish species(large mouth, sunfish, perch) have taken over.
Small fish nursery areas north of the turn bridge are no longer functioning as they have in the past. The resulting explosion of sunfish in closed off nursery areas over the last 10 years has crippled river fish reproduction and possibly ended the return of river fish to traditional spawning areas. Sunfish are voracious eaters of eggs, fry and macroinvertebrates. My observations of declining Damsel and Dragonflies in nursery areas lend support to this theory. River fish and minnows are host species for freshwater mussels to reproduce. There has also been a massive decline in many of these mussel species. Shell Middens(piles of shells) from muskrats used to be very common along the edges of the river. Now they are much less common.
Changes to the Saint Croix over the last 10 years are easily visible and profound. Climate change and pollution is not a reasonable explanation. I truly believe the dam flow changes were orchestrated with the best of intentions for river preservation and protections. Unfortunately the results have not been as beneficial as we had hoped. After 14years the river is reaching a much less bio-rich equilibrium. Will anyone step up to restore the river to the previously wealthy, biodiverse river of years past?
As old time stewards of the river retire, there is a generational cognizance lost forever. Soon nobody will remember what the river was like before the dam flow change. A more prolific lake fishery and its corresponding reduction of river fish species is the new norm for the St Croix. New generations of river stewards will readily accept the current river assuming that all is normal.
With fewer river fish, fewer river minnows equating to fewer mussels… It may be time to ask a different question. The current mindset has focused on what “changes” can be made to protect the river? I believe we should be asking what has made the St Croix one of the best freshwater fish and mussel beds in the world? Monumental changes have been made to an area historically known for extraordinary natural wealth. The adage “If it works, don’t fix it” may apply in this situation.