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°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.KEY WORDS: Elasmobranch · Skate · Reproduction · Egg case · Undersea canyon · Nursery · Alaska Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 403: [243][244][245][246][247][248][249][250][251][252][253][254] 2010 Lauth & Acuna 2009). Combined these 3 species constitute > 95% of the skate population and biomass in the entire EBS (20 to 1200 m depth) and are the major components of skate bycatch in non-target commercial bottom trawl and longline fisheries (Stevenson 2004). Other important slope-dwelling species in the EBS include the whiteblotched skate B. maculata, the mud skate B. taranetzi, the Commander skate B. lindbergi and the whitebrow skate B. minispinosa (Hoff & Britt 2009).This study focuses on identification of skate nursery habitat for 3 abundant skate species in the eastern Bering Sea. Four nursery sites for the Alaska skate, 2 nursery sites for the Aleutian skate, and 2 nursery sites for the Bering skate ( Fig. 1) are described. Some important biological aspects examined were skate and skate egg case composition, egg case densities and predation on juvenile skates. Nursery habitat parameters include location, temporal use, depth, temperature, bottom topography and associated sessile fauna EasternBering SeaGulf of Alaska P e rv e n e ts C a n y o n P r ib il o f C a n y o n B e r in g C a n y o n MATERIALS AND METHODSNursery habitat identification. Initial locations of nursery sites were identified based on fisheries data, and previous survey trawls in which large numbers of skate egg cases were reported in the catch. Identified sites were subsequently sampled using bottom trawls in an adaptive sampling approach to identify the egg...

The use of more than a single nursery habitat type is examined for oviparous elasmobranchs using data summarized from studies conducted on the Alaska skate Bathyraja parmifera and the Aleutian skate Bathyraja aleutica in the eastern Bering Sea. The eastern Bering Sea skate species use two discrete areas as nurseries, one for egg deposition and a second for newly emergent juveniles. Egg deposition sites were located along the outer shelf and upper slope near canyons in the eastern Bering Sea. Newly emergent juveniles were found along the outer and middle shelf for B. parmifera and deep-slope for B. aleutica, suggesting that habitat used by newly emergent juvenile skates is distinct from habitat used for egg deposition and embryo development. In reviewing many studies on oviparous elasmobranchs, similar patterns emerge of habitat use during their early life history. To distinguish these distinct habitats, appropriate terminology is proposed. Egg case nursery is suggested for areas of egg deposition and juvenile nursery is suggested for areas where juveniles aggregate after emergence. Criteria to describe each habitat type are outlined.

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