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MASS MARKING TRAILERS MAKE LAST STOP AT IRON RIVER NATIONAL FISH HATCHERY
Midwest Region, September 30, 2013
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Longtime Iron River employee, Mary Reijo, enjoys her time helping out in the mass marking trailer.
Longtime Iron River employee, Mary Reijo, enjoys her time helping out in the mass marking trailer. - Photo Credit: USFWS Photo
Mass marking biologist, Allen Lane, from the Green Bay office fills buckets with fish, which will be marked and tagged.
Mass marking biologist, Allen Lane, from the Green Bay office fills buckets with fish, which will be marked and tagged. - Photo Credit: USFWS Photo
U.S. Fish and Wildlife Service employees, hard at work inside a mass marking trailer.
U.S. Fish and Wildlife Service employees, hard at work inside a mass marking trailer. - Photo Credit: USFWS Photo

For a couple of weeks a year the staff working at Iron River National Fish Hatchery in Iron River, Wisconsin, more than doubles when a tagging crew arrives in late September to mark and tag all 1.6 million juvenile lake trout on site. The mass marking program is managed through the Green Bay Fish and Wildlife Conservation Office, made up of four specialized trailers and staff, which travel across the Great Lakes states, tagging a variety of species within the basin.

Why mass marking? Little is known about survival, contribution, and reproduction of releases species, return data from Coded-Wire-Tags allows for these parameters to be analyzed by researchers. This data is then passed to managers who can make informed decisions based on scientific reviews.

What is a CWT? Coded-Wire-Tag or CWT is a 1.1mm long stainless steel wire marked with codes. This tag is injected into nasal cartilage, a relatively innocuous procedure, using a needle. Once released, the fish can be differentiated from wild fish based on a fin clip (usually the adipose fin - located behind the dorsal fin, on the back of the fish). Recapture allows for extraction of the CWT connects the fish to a release group and all data related to those fish. Data allows for population level parameters to be measured, such as: Survival, Reproduction, Growth, Contribution (percentage of total population), and Movements.

Why use a mass-marking trailer? Mass-marking trailers allow for quick, efficient marking and tagging of fish, and workforce reduction of approximately 2,500 hours at Iron River National Fish Hatchery. All fish pass through the trailer, are measured, shunt to a tagging machine by size, held in place while injected, and adipose-fin clipped. Under- and over-sized fish are hand tagged and clipped by employees in the rear of the trailer. Prior to release, a sample for each tag code is analyzed to define tag loss or missed fin clips. Mass-Marking trailers visit Iron River National Fish Hatchery, Jordan River National Fish Hatchery, and Pendills Creek National Fish Hatchery, which are all part of the Midwest Region's Lake Trout Program.  Marked fish are released to Lake Huron and Lake Michigan. The majority of Iron River lake trout are released into Lake Michigan.


Watch mass marking in action!
http://youtu.be/stnm2Y_KHBo
Contact Info: Shawn Sanders, (715)372-8510, Shawn_Sanders@fws.gov



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