Identification of skate nursery habitat in the eastern Bering Sea

Identification of habitat used for skate egg deposition has been rarely studied or reported worldwide. Four nursery sites for the Alaska skate Bathyraja parmifera, 2 for the Aleutian skate B. aleutica and 2 for the Bering skate B. interrupta were identified along the upper continental slope in the eastern Bering Sea. All sites were located near undersea canyons from 145 to 380 m depth in relatively flat sandy to muddy bottom habitat. Bottom temperatures were relatively constant throughout the year, varying from 3.7 to 4.6 degrees C. Egg case densities varied between nursery sites and were encountered at the Alaska skate nursery in Bering Canyon at densities greater than 800 000 eggs km(-2). Based on egg case composition, sites were predominantly used by a single skate species for egg deposition; however, up to 6 skate species used the habitat commonly. Seasonal sampling indicated that sites were continuously occupied throughout the year, and embryo length composition showed multiple cohorts developing simultaneously. Data from bottom trawl surveys suggest juvenile skates occupy habitats different than nursery sites. The movement of juvenile skates out of nursery habitat after hatching may lessen predation by common predators such as the Pacific cod Gadus macrocephalus and the Pacific halibut Hippoglossus stenolepis,