by Mike Reiter
Polk County Naturalist
On April 12th, my wife, Sally, and I attended an extremely interesting talk by Dr. John Lyons, Curator of Fishes at the University of Wisconsin Zoological Museum in Madison. It was held at the River Falls Library and titled “Fish of the St. Croix: Past, Present and Future” and sponsored by the St. Croix River Association.
John did a great job of laying out the changes that have occurred over the last two hundred years since European expansion on the fishery populations and extended his thoughts as to what it might look like 100 years into the future. He focused on the St Croix River watershed, which includes all the tributaries of the St Croix River including the Willow, Apple, Kinni and several on the Minnesota side.
Early writings on the area mention the predominate fish at that time which included brook trout, lake sturgeon, redhorse and least darter. They were probably much more prevalent back 200 years ago. Several things happened that greatly affected the areas lakes and rivers since the early settlement.
Beavers were nearly eliminated by the mid 1800’s due to the value placed on their fur by European fashion demands. The coarse guard hairs of beaver provided “felt” that made the beaver hats very popular at that time. With the beavers almost wiped out, the streams they had dammed were opened and fish habitat that the dams provided was greatly affected. Fish population types changed dramatically in those areas.
Timber cutting of the vast white pine forests and other valuable timber species caused a marked change in the area logged off. Erosion followed deforestation and the rivers and lakes were choked by the runoff. The rivers became the means of moving the huge quantity of logs to the lumber mills. The physical abuse of the logs being moved greatly gouged out the shorelines and widened the banks making the waterways shallower. Log jams needed to be cleared and blasting of them were a common means of getting the logs back into the flow of the river.
Increased agriculture in areas of the northern watershed that was not good farmland caused increased erosion and sedimentation. Removing vegetation and plowing of marginal cropland exposed the sandy soils to further soil loss. All this ended up in the lakes and streams. Formerly deep river channels became shallow shadows of themselves.
Eutrophication of the watershed was hastened further by raw sewage being dumped into streams and rivers and industrial pollution from factories and other facilities hastened the demise of water quality. Damming of rivers and streams also markedly transformed the way fish could migrate to spawning areas and water backed up behind the impoundments caused further water quality changes.
Introduction of invasive species by planned stocking or by accidental escapes greatly changed the area fisheries make-up. Carp at one time were considered a valuable food fish and were actively stocked in the 1870’s to provide what was thought of as a welcome addition to our rivers and lakes. They presently are now considered a detriment to aquatic habitat and out-compete much more desirable fish species. Brown trout from Europe were stocked in our cold water streams and presently provide a better outcome than the carp but do have a downside as they compete for habitat with our native brook trout. Muskies were not present in the St Croix River system until the 1920’s for whatever reason but now are increasing in numbers. Walleyes, while present back in the early days, are now becoming much more prevalent in our waterways.
Habitat and weather changes have shifted the fish populations of the watershed markedly. The St Croix River fishery had proven to be remarkably resilient however. Our fish population remains one of the most diverse in the nation.
The advancement of modern sewage treatment has led to huge water quality improvement since the 1950’s. Beaver populations have rebounded and expanded. Reforestation of our northern forested areas has returned land cover and now provides much better habitat for all wildlife. Our river channels are healing and deepening. Thinks are looking up!
While the future looks bright, we are still facing severe changes that will affect us all including the fisheries and all wildlife. Increased urbanization will continue to put pressure on our natural resources. Invasive species will continue to modify our aquatic communities and the increasing demand on water and its quality and availability will become more intense as we move forward!