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Red Bluff Fish & Wildlife Office
Pacific Southwest Region

Hatchery Evaluation - Coded-wire tagging

Coded Wire Tag shown on a finger tip for reference

Coded Wire Tag shown on a
finger tip for reference
PhotoCredit: Northwest Marine Technology, Inc

Coded-wire tags are an important tool biologists use to manage fisheries and evaluate hatchery programs all along the Pacific coast. A coded-wire tag is a small piece of stainless steel wire, measuring about one quarter of a millimeter in diameter and about a millimeter in length. On the barrel of the tag a unique code is inscribed. The tag is inserted into the cartilage of the fishes snout. Typically, the adipose fin is removed from coded-wire tagged fish as a visible mark to identify them as containing a tag. The coded-wire tag will remain in place for the entire life of the fish. When the fish is harvested or returns to the hatchery as an adult the tag will be recovered and decoded with the aid of a microscope. By applying this tag to a juvenile fish and recovering it later in the fish’s life, biologists can associate information from the two life stages and gather important information that is used to make management decisions. For example, biologists use coded-wire tags and the associated fin clip to gather information such as the harvest rate and straying of hatchery fish.

Fish having Coded Wire Tag embedded

Fish having Coded Wire Tag embedded
PhotoCredit: USFWS

Currently, about 4 million juvenile salmon are coded-wire tagged each year at the Coleman National Fish Hatchery, including three million fall Chinook (25% of the hatchery’s production) and 1 million late-fall Chinook (100% of the hatcheries production). Steelhead produced at the Coleman NFH are not currently coded-wire tagged, however, all of the steelhead produced at the Coleman NFH are marked by removing their adipose fin to identify them as being of hatchery origin. All of the winter Chinook salmon produced at the Livingston Stone National Fish Hatchery are coded-wire tagged.

Coded Wire Tag embedded in the nose of a fish

Coded Wire Tag embedded
in the nose of a fish
PhotoCredit: USFWS

Coded-wire tagging of fall Chinook salmon at the Coleman National Fish Hatchery is part of a larger basin-wide program to mark and coded-wire tag a consistent portion of fall Chinook salmon from Central Valley salmon hatcheries. This program is called the Constant Fractional Marking (CFM) Program. A coded-wire tag rate of 25% has been used at Central Valley salmon hatcheries since 2007. As part of the CFM, over eight million fall Chinook salmon are marked and tagged each year at five Central Valley salmon hatcheries. To mark and tag this large number of fish requires the use of highly sophisticated, state-of-the-art automated tagging trailers. The primary goal of the CFM program is to estimate the relative harvest and abundance of hatchery and naturally produced fall Chinook salmon.

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Last updated: August 22, 2014