Fish with Missing Adipose Fin FAQ

The Department of Natural Resources (DNR) fisheries biologists track fish for research purposes. There are various ways DNR marks fish which are part of these research studies:

• a tag is attached to the fish, or
• a radio transmitter is implanted, as noted by a wire antenna, or
• a code wire tag is implanted, as identified by a missing adipose fin.

DNR discourages anglers from tagging their own fish.

Should you catch a DNR tagged fish, it is very important to report the requested information promptly. The information provided by the angler helps DNR to determine fish population estimates, and harvest and exploitation rates. In some cases, these studies have been going on for years. Your cooperation and participation is greatly appreciated.

If you release the fish, please do not remove the tags.

Adipose Fin Clip

Fish biologists want to learn more about trout and salmon in Lake Michigan to improve rearing techniques and the management of the fishery. When these fish are stocked, they are too small to use conventional tagging techniques to mark them. Over the past two decades, the DNR has utilized coded wire tags (CWTs) to mark numerous study groups of trout and salmon fingerlings. CWTs are very small (i.e., smaller than this minus sign -) pieces of stainless steel wire that are etched with a binary code and injected into the snout of trout and salmon fingerlings before stocking. To identify the fingerlings which have been implanted with a CWT, the adipose fin is removed as shown below:

This disgram shows a fish with a missing adipose (back) fin.

Requested Information and Notifying the DNR

If you catch a fish missing ONLY its adipose fin, please record the fish's length and the date and location caught. Freeze the head and drop it off at one of the following DNR offices or cooperating businesses.

DNR Offices

DNR Service Center
1155 Pilgrim Road, Box 408
Plymouth, WI 53073
(920) 892-8756 - phone
(920) 892-6638 - fax

DNR Service Center
1125 N Military, PO Box 10448
Green Bay, WI 54307
(920) 492-5800 - phone
(920) 492-5913 - fax
(920) 492-5912 - tdd

DNR
2220 E County Highway V
Mishicot, WI 54228
(920) 755-4982 - phone - hours vary, call ahead
(920) 755-4981 - fax

DNR Peshtigo Service Center
101 N Ogden Road
Peshtigo, WI 54157
(715) 582-5001 - phone
(715) 582-5005 - fax

DNR Service Center
110 S Neenah Avenue
Sturgeon Bay, WI 54235-2718
(920) 746-2860 - phone
(920) 746-2863 - fax

DNR
Water Institute
600 East Greenfield Avenue
Milwaukee, WI 53204
(414) 382-7929

DNR Southeast Region
2300 N Dr. Martin Luther King Drive, PO Box 12436
Milwaukee, WI 53212
(414) 263-8500 - phone
(414) 263-8606 - fax

Cooperating Businesses

You may also freeze the head and drop it off at the following locations:

Algoma True Value
410 2nd Street
Algoma, WI 54201
(920) 487-3374

Jalensky's Sport Headquarters
5803 52nd Avenue
Kenosha, WI 53142
(262) 654-2260

Racine Fish Cleaning Station
5th Street
Racine, WI 53402
(262) 632-5040

Riverfront Bait & Tackle
733 Riverfront Drive
Sheboygan, WI 53081
(920) 458-4406

Hole 'N One Mobil Station
Sturgeon Bay, WI 54235
(920) 743-8772

Seagull Sports Marina
1400 Lake Street
Two Rivers, WI 54241
(920) 794-7533

If you include your name and address, DNR will respond with the stocking history of this fish.

To help encourage anglers to participate in this reporting program and through the generosity of various lure manufacturers, DNR is able to send out a lure for each trout or salmon head received from an angler that contains a CWT.

Ongoing Chinook Salmon Studies

Currently several chinook salmon studies are being conducted. Chinook from these studies were released over the past several years and are beginning to return to the spawning weirs.

In one study, chinook hatched from eggs treated with thiamine are returning to the spawning weirs in as good or better health than chinook that were not treated with thiamine as eggs. DNR treats trout and salmon egges with thiamine just after fertilization to reduce the early mortality problems that agencies around the Great Lakes have been experiencing. This longer-term study shows that in addition to getting more of the fertilized eggs to hatch and survive to stocking, there is no negative long-term effect of thiamine treatment.

Other CWT chinook studies currently in progress include a study in which fingerling chinook from four-year-old parents are being compared with the fingerlings from three-year-old parents. There is evidence from chinook studies on the west coast that the age of maturity in chinook salmon is an inheritable trait. If this proves true of our Lake Michigan chinook -- and we can shift most of our chinook to maturing at four years, instead of three years -- we could get an extra year of fishing out of these fish. Also, the average size of chinook in the sport catch should go up a little.

In another CWT chinook salmon study on in the Kewaunee River system, chinook salmon fingerlings are being stocked at various distances from Lake Michigan. Previous studies have shown that stocking chinook fingerlings in rivers is more effective than stocking them directly into Lake Michigan. This study builds on the previous studies and will hopefully allow DNR to stock our chinook more effectively.

For more information on fish with missing adipose fins, please contact: Paul Peeters, Fisheries Biologist.

If you catch a fish with a tag, please see our web page on catching a tagged fish.

If you catch a fish with a wire antenna, please see our web page on catching a fish with a wire antenna.

If you are unsure who to report your information to, please contact the Bureau of Fisheries Management.