Wednesday, February 23, 2011

AKCRRAB Conducts Juvenile Red King Crab Tagging Study

AKCRRAB biologists are developing methods to identify hatchery-raised king crab using physical tags. Their experiments test crab survival and retention of tags after molting for a range of juvenile crab sizes. The methods are modeled after similar efforts in Chesapeake blue crab.

From October 2010 to February 2011, Alaska Sea Grant research biologist Jim Swingle conducted a tagging study using coded wire tags, visible implant elastomers, and dactyl clipping on juvenile red king crab. Each method was tested on three different size classes of juveniles (5, 10, and 15 mm carapace width) to determine the minimum size juveniles could be effectively tagged. The experiment was run until all tagged juveniles molted at least once, so that tag retention could be measured post-molt. The findings suggest that juveniles of 10 mm CW and larger can be marked with low levels of mortality and high post-molt tag retention rates using both coded wire tags and visible implant elastomers. The mark from dactyl clipping was lost. Because the elastomers are likely to become more difficult to detect as the animals increase in size and their shells become increasingly opaque, the coded wire tags are more likely detectable over the lifetime of the animal.

The experiment was conducted at the University of Alaska Fairbanks Lena Point facility in Juneau, Alaska, using juvenile crabs reared at the Alutiiq Pride Shellfish Hatchery during 2010 production experiments. These tagging methods should prove useful to researchers and resource managers interested in further exploring the feasibility and effects of a king crab stock rehabilitation program.

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