Testing new electronic archival tags in Alaska salmon

Objective 2

Tag each coho salmon for individual identification and record retention rate.

Close-up of VI-alpha tag used on arctic char1

Soft visible implant tags known as VI-alpha tags were used to individually mark each coho salmon for the 2001 release.  The tags are injected with an adapted syringe under the adipose eyelid directly behind each eye.  This tissue is clear and allows for visual identification of marked coho.  Each tag is numerically and color-coded to allow for individual identification.  In dark or cloudy conditions, an U.V. light can be used to enhance the brightness of the tag and code.

¹ - Audun H. Rikardsen, 2000. Effects of floy and soft VI Alpha tags on growth and survival of juvenile arctic char.  N. Amer. J. Fish. Mgmt., 20(3).

Close-up of VI-alpha tag under UV light used on juvenile coho salmon

Coho greater than 150 mm (FL) were tagged with individually identifiable VI-alpha tags in sub-sets taken from the study population.  Two different sizes in three different colors were randomly used to tag coho.  Preliminary results found that within four weeks of being VI tagged, there was a 31% tag loss.  Tag loss can be attributed to a lack of tagging experience by biologists, handling stress, and size of tag in relationship to fish size.

Inserting a PIT tag into a coho pre-smolt

Following the 2001 summer / fall search for returning tagged coho, project biologists decided to use PIT tags to aid in the efficiency of sampling the large return of spawning adult coho for archival tagged fish.  A PIT tag, manufactured by Biomark, is a small 11.5 mm by 2.1 mm glass cylinder equipped with a 12 digit bar code which transfers an individual number to a receiver when scanned by a PIT tag receiver.  They are injected into the body cavity of fish using a sterile syringe and 12 gauge needle.  The tags are placed inside the needle and a plunger gently pushes the PIT tag into the body cavity. With the use of a portable receiver and antenna, the large volume of returning adult coho to Ship Creek each summer and fall can be more readily scanned for tags as they are passed through the ADF&G fish weir as well as during daily stream surveys looking at local sport fishing captures.

Scanning a newly PIT tagged coho

(continued to Objective 3)

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