1,100 ruffe were captured in a five-minute bottom trawl from the Duluth/Superior Harbor of Lake Superior. - FWS photo

The Ashland Fishery Resources Office provided technical assistance to the U.S. EPA Laboratory, Duluth, Minnesota, in developing an aquatic invasive species (AIS) early detection monitoring protocol. 

The study location was the Duluth/Superior Harbor, St. Louis River Estuary,  in both Minnesota and Wisconsin.  The EPA lab is studying sampling methods for early detection of both invasive fish and aquatic invertebrates. 

Fish sampling methods included electrofishing, trapping, and bottom trawling.  The Ashland FRO assisted with the trawling phase by providing a smallcraft trawler and an operator/biologist. 

A trawl was specially configured with a fine mesh liner for capturing larval, juvenile and adult fish.  A total of 40 five-minute tows were completed in three days at point locations and zones representing a spectrum of trawlable habitats identified by the EPA.  Captured AIS included ruffe, round and tubenose goby, white perch, common carp, and zebra mussels.  All of these AIS are reproducing in the St Louis River Estuary. 

AIS catches of interest included 1,100 ruffe from one tow near a sewage treatment facility, and two common carp, each measuring nearly three feet in total length, from separate tows in diverse habitats. 

One carp was captured from a dredged heavy boat slip with a clay substrate.  The other large carp was captured far upriver in an undisturbed natural channel containing woody debris.  

Ruffe were the most abundant of all invasive fish captured, and were present in nearly all tows.  No new AIS were detected in the St. Louis River Estuary trawls. 

The Ashland FRO also participated in a workshop conducted previously by the EPA lab to suggest methodology for this AIS early detection case study.