Distribution and movement of juvenile tanner crabs Chionoecetes bairdi in Glacier Bay National Park

Abstract

Spatial segregation of adult and juvenile Tanner crabs was observed in conjunction with glacial landscape features during a comprehensive systematic survey of Glacier Bay National Park, Alaska, in 2002. Hot spots (clusters of high values) of catch per unit effort for juveniles occurred mainly in two narrow glacial inlets, whereas most adult hot spots occurred in the central portion of the bay. Overall, juveniles were associated with shallower depths and warmer temperatures than adults. However, in juvenile hot spot areas, where adults were rare, juveniles were associated with greater depths and colder temperatures than adults. Glaciated landscapes may provide spatial refuges from predation and nursery areas for juveniles. Tagging methods with high trans-molt retention need to be developed for direct measurement of ontogenetic movement. A laboratory study was conducted to determine trans-molt survival and retention of Floy T-bar tags in juvenile Tanner crabs. Approximately half of crabs in all tagging treatments survived and retained tags through a molt. Trans-molt retention of Floy tags is hindered by complex morphology of the Tanner crab carapace.