Identification of multiple nursery habitats of skates in the eastern Bering Sea

Abstract

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.

Deep-sea hydrothermal vents as natural egg-case incubators at the Galapagos Rift

“…In addition to decreasing egg incubation periods, this is the first record of a hydrothermal vent habitat serving as an egg-case nursery site, a discrete habitat with extremely high densities of egg cases when compared to surrounding similar habitats 16 . Among the elasmobranchs, skates are the only group known to be strictly oviparous, where females produce large collagen egg cases containing a large yolk mass 22 , 23 .…”

“…The presence of a B. spinosissima egg-case nursery (as described by 16 ) in an active hydrothermal vent field, where even the temperatures several meters above the substrate were often higher than ambient water, implies that this species is utilizing heat at the active Iguanas-Pinguinos vent site to incubate its egg-cases. We hypothesize that this behavior is directly targeted to accelerate embryo development times.…”

“…Egg-case nursery sites for members of the genus Bathyraja have been previously identified across most ocean basins and in diverse habitats like rocky reefs, submarine canyons, seamounts or even methane cold seeps 17 , 24 , 25 . Hydrothermal vent sites may also have other advantages as a juvenile nursery, although previous studies have revealed that juvenile skates of other species of the genus Bathyraja leave egg-case nurseries after hatching 16 , 26 .…”

“…This fully non-extractive reserve also protects adjacent seamounts, and it includes the Iguanas-Pinguinos vent site, thus protecting the first known nursery for deep-water predators associated with active hydrothermal vents. In 2015, the North Pacific Fishery Management Council designated eight deep-sea skate egg-nurseries in the eastern Bering Sea as habitat areas of particular concern, and this represented the first official recognition of this habitat type worldwide 16 . Further research should focus on identifying and promoting the protection of additional Chondrichthyan deep-sea nurseries, given the continuous expansion of fisheries towards the deep-sea and the intrinsic vulnerability of this group of species 32 – 34 .…”

Skate-ing on thin ice: molecular ecology of longnose skates in the Southeast Pacific Ocean

“…Natal philopatry is well-recognised among various marine vertebrates including elasmobranch fishes, but while it has been shown definitively for sharks (Hueter et al, 2005;Dudgeon et al, 2012;Feldheim et al, 2014;Chapman et al, 2015;Hoff, 2016), the situation in skates is less clear. Tagging studies have indicated that skates may have the potential to travel hundreds of kilometres (Templeman, 1984;Hunter et al, 2005), however, 90% of individuals had a relatively small home range (within a 100 km 2 area) (Walker et al, 1997;King et al, 2010;Farrugia et al, 2016).…”