A nursery site of the Alaska skate (Bathyraja parmifera) in the eastern Bering Sea

Elasmobranchs are of growing concern worldwide because they are threatened by increased fishing and habitat disturbances (Musick et al., 2000; Stevens et al., 2000). Characteristic life history traits of these fish include slow growth rates, late maturation, low fecundity, and long life-spans, all of which make them extremely vulnerable to increased fishing-induced mortality (Dulvy, 1999; Frisk et al., 2002). Species with these life history patterns depend on high juvenile survival and recruitment for population stability. An adequate understanding of reproduction dynamics and habitat requirements are lacking for most species, yet these may be the most critical biological criteria for successful reproduction. Oviparous species such as skates (Rajidae) use nursery areas for egg deposition, embryo development, and hatching (Hitz, 1964; Hoff, 2007). They produce relatively large collagen egg cases (Knight et al., 1996) which contain a large yolk mass and developing embryo. The egg cases are deposited directly onto the seafloor and embryos develop independent of maternal care (Hamlett and Koob, 1999). The embryonic developmental period is unknown for most species of skates, but evidence indicates that it may exceed one year for temperate and deepwater species (Berestovskii, 1994). The Alaska skate (Bathyraja parmifera) represents >95% of estimated skate biomass on the eastern Bering Sea shelf (20 to 200 m) (Lauth and Acuna, 2007), and estimates of biomass and population numbers have indicated nearly a fourfold increase since 1975 (Hoff, 2006). Skates at A nursery site of the Alaska skate (Bathyraja parmifera) in the eastern Bering Sea