Overview

Comprehensive Description

Biology

Oviparous. Distinct pairing with embrace. Young may tend to follow large objects, such as their mother (Ref. 205). Eggs are oblong capsules with stiff pointed horns at the corners deposited in sandy or muddy flats (Ref. 205). Egg capsules are 10.6-12.0 cm long and 7.54-7.8 cm wide (Ref. 41253, 41249, 41250, 41298). Depth range given by H. Ishihara (pers.comm. 07/07).
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Distribution

Range Description

Northwest Pacific: endemic to Japan, Southern Hokkaido to Choshi, Honshu (Ishihara 1990, Dolganov 1998).
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Northwest Pacific: off northern Japan.
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Japan.
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
A medium sized deepwater skate, found on lower shelf and upper continental slope at depths between 100-1,000 m (Ishihara 1990). Maximum recorded size is 87.7cm total length (TL) for females and 85.9 cm TL for males (Dolganov 2005). Females mature at 5-7 years, reaching a total length of 67-70 cm and males mature at 5?6 years, reaching a total length of 64-69 cm (Dolganov 1998). Egg capsules are 10.6-12.0 cm in length and 7.6-7.8 cm wide (Dolganov 1998). Virtually nothing else is known about this species? ecology and biology. Reproduction is presumably oviparous like other skates.

Systems
  • Marine
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Environment

demersal; marine; depth range 400 - 800 m
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Life History and Behavior

Life Cycle

Oviparous, paired eggs are laid. Embryos feed solely on yolk (Ref. 50449). Distinct pairing with embrace. Young may tend to follow large objects, such as their mother (Ref. 205).
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2009

Assessor/s
Ishihara, H., Orlov, A. & Huveneers, C.

Reviewer/s
Gibson, C., Valenti, S.V. & Fowler, S.L. (Shark Red List Authority)

Contributor/s

Justification
The Duskypink Skate (Bathyraja diplotaenia) is a medium-sized (88 cm TL), primarily deepwater skate. This northwest Pacific species is endemic to Japan, found at depths of 100?1,000 m. Females mature at 5?7 years, males at 5?6 years. It is caught as bycatch at depths of <500 m, and retained by the bottom trawl fishery targeting cod and rockfish. This fishery only operates to 500 m depth and therefore only impacts the species over the shallower part of its bathymetric range. Given that the majority of the species? area of occurrence is thought to lie beyond the range of current fisheries, it is assessed as Least Concern at present. However, as the species may have limiting life-history characteristics, similar to other deepwater skates, the situation should be very carefully monitored. If fishing effort increases or expands further throughout its area of occurrence, then this assessment should be revisited. Species-specific assessment and monitoring of current catches, as well as research on the impact of fisheries-related mortality would also be beneficial.
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Population

Population
Very little is known about the population of this species.

Population Trend
Unknown
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Threats

Major Threats
This species is caught as bycatch and retained by the bottom trawl fishery targeting cod and rockfish. This fishery is reported to impact this species in the upper part of its bathymetric distribution only (to 500 m depth), offering refuge beyond the range of fishing pressure (H. Ishihara pers. obs.). Increased fishing pressure, particularly and expansion of pressure into deeper water, could pose a threat to this species.
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Least Concern (LC)
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Management

Conservation Actions

Conservation Actions
No management or conservation measures are currently in place. Like many deeper water species more information on biology, ecology and importance in fisheries are required. Given the species? limited range, catches need to be monitored and further study of the impact of fisheries on this species is required.

The development and implementation of management plans (national and/or regional e.g., under the FAO International Plan of Action for the Conservation and Management of Sharks: IPOA-Sharks) are required to facilitate the conservation and management of all chondrichthyan species in the region.
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