Testing new electronic archival tags in Alaska salmon

Objective 3

Implant archival tags into a sub-sample of juvenile coho

By early spring 2001, the accelerated growth program provided a sub-sample of coho large enough to be implanted with inactive archival tags.  The tags were provided by LOTEK, a Canadian company specializing in fish and wildlife electronic monitoring tools.  We are working with LOTEK in the development and implementation of this new tagging technology. Our goal was to test surgical techniques and survivability of young salmonids implanted with these tags.  A total of 60 coho were implanted with inactive archival tags.  Average measurements for the tagged coho were 199.11 mm (FL) and 94.72 g.  Tag specifications were 11x36 mm tubular form weighing 6.8 grams.  The tags averaged 7.28% coho body weight. 

Archival tagged coho salmon

Great care was taken to ensure a high level of survival for implanted coho salmon.  Each coho was initially anesthetized in a clove oil solution. A separate pack of sterilized surgical tools was used for each fish surgery.  All tags and equipment were thoroughly sterilized and biologists operating on the fish wore sterile surgical gloves.  After implanting the tag, coho were immediately placed into a tub of fresh flowing cool water (10 oC) that was highly oxygenated (>96%) to aid in fish recovery. Average coho recovery time was eight minutes.  As soon as a fish recovered equilibrium and was swimming independently, tagged coho were placed into a portion of a large indoor raceway at Fort Richardson Hatchery.  They were observed for up to two weeks before being released.  Out of 60 internally tagged coho, we had two mortalities, one to two days after
	Biologist Derek Wilson (back) and DMV Dan Mulcahy (front) implanting coho with archival tags.
surgery.  One other mortality occurred after the transfer to Elmendorf Hatchery, resulting in a 95% post-surgical survival rate.  An autopsy was performed for each mortality and we found no obvious handling injuries or impoundments resulting from the surgery.  Stress from the surgical process and smoltification were likely contributing factors. The following spring produced similar surgical archival tagging success.  The accelerated growth program produced enough coho of size for a total of 174 to be tagged and released with active archival tags.  The average measurements for the 2002 tagged coho were 199.95 mm (FL) and 91.68 g. The active tags were slightly smaller than the previously used in-active tags in part to manufacturing progress,  resulting in an average of 5.73% of the coho body weight.   With small improvements made to the tagging process, we were able to observe the tagged coho for up to 32 days before release and increase the post-surgical survival rate to 97%.

Click on thumbnails for larger versions of the pictures below

Biologist performing tag implant surgery on coho salmon	Suturing an incision on a coho	Biologist preparing surgical packet for surgery	Sterilized open surgical packet for individual fish

(continued to Objective 4)

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