Current Ideas: Lower Wisconsin State Riverway Fish Survey

by David Marshall

Editor's Note: There will be a talk given by Dave Marshall on this topic! Join us at St. John's Lutheran Church, in the Fellowship hall on Wednesday, May 21, 2008. Refreshments start at 6:30pm with the talk beginning at 7pm.

While most of us in this area appreciate the Lower Wisconsin State Riverway for outstanding canoeing, fishing and eagle watching, the Lower Wisconsin River is also one of the most ecologically diverse large river reaches in the United States. High numbers of fish species is one of the ways that the ecological diversity is expressed. One hundred and forty seven species of fish live within the Riverway, reflecting a free flowing river that is connected to a vast network of floodplain lakes.

Oxbow Sampling Recognizing that floodplain lakes are important and unique features of the Riverway, SP River PAL received a State River Planning Grant in 2007 to sponsor a two year study of floodplain lakes along the entire Lower Wisconsin State Riverway. The primary goal of the study is to collect information from lakes that had either never been sampled or had not been sampled in decades. The data that we are collecting is revealing a wealth of information on near-shore fish species and water quality.

Most of the larger floodplain lakes are oxbows or former channels that became separated from the river under normal conditions. Oxbows are either completely isolated or partly connected to the river during low flow but occasionally become part of the larger river during floods. These connections influence the types of fish that live in the lakes. The existence of numerous oxbows is one of the reasons the Riverway supports so many fish species and other aquatic animals. The oxbows provide habitats for fish that avoid fast currents as well as nursery habitat for young fish that normally live in the main channel as adults.

Glass Pickeral In 2007, 46 oxbows and other floodplain lakes were sampled from Prairie du Sac to Lone Rock. Preliminary results revealed surprising populations of popular sport fish as well as rare species. Water quality sampling demonstrated that oxbows and floodplain ponds that lack either upland sources of groundwater or tributaries are generally devoid of fish due to lack of sufficient oxygen. The results indicate that protecting water quality and quantity of both groundwater and streams far beyond the floodplain benefit oxbow and river fish.

Sampling will continue in 2008.

Upper right photo shows sampling procedures in the oxbow. Lower left photo is a Grass pickerel -- a Pike family member and smaller cousin to northern pike and musky.