Ruffe graphic - Art by Gary Cholwek, USGS Total image

The Ashland Fishery Resources Office (FRO) completed summer sampling of the invasive fish, ruffe, in three Wisconsin tributaries and one Michigan tributary to Lake Superior. 

Sampling is also conducted during spring and fall, and the results are averaged to account for seasonal variation.  This ongoing investigation was initiated in 1995 to compare trends in abundance of ruffe and native fish populations, one of eight elements in the Ruffe Control Program. 

A total of 3,123 fish representing 25 species were captured in bottom trawls, including two invasive species, ruffe and threespine stickleback. 

All fish were released except the invasive species.  The total catch was 3% ruffe and less than 1% threespine stickleback, not unusual for the summer sampling.  Ruffe young-of-the-year were only strong in the Flag River, Wisconsin, which contains the most nursery habitat of the four tributaries.

Research and this long-term investigation have shown that ruffe may impact on yellow perch growth and abundance.  Yellow perch comprised just over 1% of the total catch in this sample.