Volunteer Aime Bourdon and Service Biologist Jim McFee with a young of the year and an age one lake sturgeon from the Detroit River. - FWS photo by James Boase

Service Biologist James Boase and volunteer Aime Bourdon handle a steelhead at the north end of Fighting Island on the Detroit River. - FWS photo by Jim McFee

Fisheries Biologists James Boase and Jim McFee, in conjunction with United States Geological Survey (USGS), completed a lake whitefish survey on the Detroit River.  Sampling was conducted in both US and Canadian waters in the area downstream of the City of Detroit, from October 30^th to December 4^th. 

Historically lake whitefish used the Detroit River for spawning, but in the recent past have been absent from the system.  Sampling in the fall of 2005 produced two adult lake whitefish and numerous eggs, which warranted an increased sampling in 2006.

During the sampling period several methods were used to collect information on the stock structure of this species, including gillnets, egg mats, and egg pumping equipment.  Service biologists concentrated on the gillnetting and assisted with the egg pumping, while USGS biologists focused on egg collection using the egg mats. 

Nets were fished in three zones within the sample area.  Before whitefish eggs were identified in the survey one zone was sampled per night with four 150 foot experimental gillnets.  The mesh sizes ranged from three to six inch stretch on 25 foot panels.  Once whitefish eggs were confirmed in the sampling gear netting was concentrated around the areas of egg collection.

During the first few weeks of the study drifting vegetation fouled the gillnets and diminished their effectiveness.  Once the nets are choked with vegetation they become highly visible and avoidable by fish.  As temperatures dropped the amount of vegetation in the river decreased resulting in increased catches.

Gillnetting produced no lake whitefish in 54 overnight sets, however several others species were collected.  Gillnetting revealed eleven different species, including lake sturgeon and a steelhead (rainbow trout).  Four lake sturgeon ranging in size from 365mm to 872mm received passive integrated transponder (PIT) tags and cinch FLOY tags after capture from the Fighting Island Complex, prior to release.  The 365mm lake sturgeon is a young of the year (YOY), which was the first YOY sturgeon captured in the Detroit River in 40 years of sampling by biologists.  A large, 712mm, male steelhead was also captured at the north end of Fighting Island, another rare find in the Detroit River.

Lengths were recorded for all other species, with more extensive data collected from walleye and yellow perch.  Additional data collected included, aging structures (otoliths and dorsal spines), sex data, and diet data of 33 walleye and 6 yellow perch.  Aging structures will be analyzed this winter back at the lab.

This project is an ongoing look at the lake whitefish stocks that use the Detroit River for spawning.  Sampling will continue in the fall of 2007 as water temperatures approach 10^oC.  In addition to gillnets some alternative gears may be used to capture whitefish to increase the number of adults that are handled.