Ruffe. - FWS photo

Yellow Perch. - FWS photo

Trout-perch. - FWS photo

Threespine Stickleback. - FWS photo

The Ashland Fishery Resources Office staff completed summer monitoring of the invasive fish, ruffe, and native fish by bottom trawling in three Wisconsin tributaries and one Michigan tributary to Lake Superior. 

These ongoing investigations were initiated in 1995 to compare trends in relative abundance of ruffe and native fish populations, one of eight elements in the Ruffe Control Plan.  Monitoring is also conducted during spring and fall, and the abundance results are averaged to account for seasonal variation.    

A total of 2,386 fish representing 18 species were captured including 2 invasive species, ruffe and threespine stickleback.  This compares to a total catch of 3,123 fish representing 25 species captured during this cycle in 2006. 

Trout-perch, spottail shiner, and common shiner were the three most abundant species captured, comprising 57%, 18%, and 10% of the total catch respectively.  The majority (55%) of the trout-perch were captured from the Ontonagon River, Michigan.  Walleye comprised nearly 1% of the total catch with 75% of the walleye catch consisting of young-of-the-year (YOY), and all YOY walleye were captured from the Ontonagon River. 

Ruffe comprised 1 % of the total catch compared to 3% during this cycle in 2006, and only a total of 1 threespine stickleback was captured in 2007 compared to a total of 2 captured in 2006.  In both years, threespine stickleback were only captured from the Iron River, Wisconsin.  \

No YOY ruffe were captured in this cycle, including the Flag River, Wisconsin, which contains the most nursery habitat of the four tributaries.  In 2006, YOY ruffe numbers in the Flag River had indicated a strong year class there.  Yellow perch comprised nearly 4 % of the total catch in this cycle, compared to 1% in 2006.  One third of the yellow perch catch were YOY, and all YOY yellow perch were captured from the Flag River.  All fish were released alive except the two invasive species.