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Okamejei kenojei

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES RAJIFORMES RAJIDAE

Scientific Name: Okamejei kenojei
Species Authority: (Müller & Henle, 1841)
Common Name(s):
English Ocellate Spot Skate, Spiny Rasp Skate, Swarthy Skate
Synonym(s):
Raja kenojei Müller & Henle, 1841
Taxonomic Notes: Okamejei kenojei has various morphotypes, which previously lead to some taxonomic confusion. Ishihara (1987, 1990) synonymised Raja porosa, R. fusca, R. japonica, R. tobae, R. katsukii and R. atriventralis with R. kenojei (Ishihara et al. 2002).

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2009
Date Assessed: 2007-01-01
Assessor(s): Ishihaha, H., Wang, Y., Tanaka, S. & Nakaya, K.
Reviewer(s): Valenti, S.V. & Fowler, S.L. (Shark Red List Authority)
Justification:
The Ocellate Spot Skate (Okamejei kenojei) is a common skate found from 20-120 m depth on sandy, muddy bottoms, in the northwest and western central Pacific. The biology of this species is relatively well known in comparison to other species of the Okamejei genus and it is relatively productive, with rapid maturity and high fecundity. This species is captured in gillnets, bottom longline and trawl fisheries. It is targeted in some areas (such as Korea) and taken as utilised bycatch in others (such as Japan and China). No species specific information is currently available on catches or temporal trends, although total landings of skates and rays declined since 1947, mainly due to a decrease in catch in the East China Sea. Although this species has relatively productive life-history characteristics, parts of its range are intensively fished, it is targeted in some areas and further study is required to determine population trends. As such it cannot be assessed beyond Data Deficient at present.

Geographic Range [top]

Range Description: Northwest Pacific: widespread throughout eastern Asian waters. China, from Bohai Sea to Shanghai, Amoi and Taiwan Island; Korea, Baereungdo Islands, Northern Yellow Sea to Jeju-do Islands; Japan from northern Hokkaido to off Kyushu; Yellow Sea, East Sea (Sea of Japan), Sea of Okhotsk, East China Sea, South China Sea (Ishihara 1990, Jeong 1999). Also known to occur in the Western Central Pacific (Last and Compagno 1999), but its extent of occurrence within this region is uncertain.
Countries:
Native:
China; Japan; Korea, Democratic People's Republic of
FAO Marine Fishing Areas:
Native:
Pacific – northwest; Pacific – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: There is no population information for this species but it is reportedly common throughout its range (H. Ishihara pers. obs.).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: This is a benthic species that lives on sandy, muddy bottoms. Occurs from 20-120 m depth (H. Ishihara pers. comm.).

Size at birth is between 8.2 and 9.5 cm TL (Abe 1983, C.H. Jeong unpublished data). It reaches a maximum size of 55-60 cm total length (TL) (Ishihara 1987, C.H. Jeong unpublished data). Ishihara et al. (2002) described the reproductive biology of this species based on 134 female specimens collected from Japanese waters, and observations of three live skates in the Oh-arai aquarium. Females were found to mature at 39 cm total length (TL).

The age at maturity of this species is around three years, which is very rapid compared to many other elasmobranchs, although no separate estimates have been made for each sex. Longevity is at least nine years in captivity .and may not exceed more than four years in the wild, although the lifespan of captive skates may reflect the life span in a natural environment (Ishihara et al. 2002, Ishimaya 1951).

The gestation period is recorded at 63-80 days (at an average daily temperature of 25ºC) (C.H. Jeong et al. unpublished data), 128-146 days (average daily temperature 14.6ºC) and about 130 days (average daily temperature 14ºC in captivity Abe 1983). Females reproduce throughout the year, except in January, and their fecundity is estimated to be higher than many other skates due to a lifetime fecundity of at least 300 capsules, with some individuals producing up to 600 egg capsules over four years (Ishihara et al. 2002). Egg-capsules are produced alternately from left and right oviducts and intervals between egg-laying were usually found to be three to six days (Ishihara et al. 2002). C.H. Jeong (unpublished data) found that one or two egg-capsules were produced per day, with one to three day intervals between egg-laying. The fecundity of this species is aided by a switch from somatic to reproductive growth after it reaches around 55 cm TL (Ishihara et al. 2002).

Eggs are oblong capsules with stiff pointed horns at the corners deposited in sandy or muddy flats. Egg capsules are 4.8-6.6 cm long and 2.9-3.7 cm wide (C.H. Jeong unpublished data).
Systems: Marine

Threats [top]

Major Threat(s): This species is thought to be one of the most dominant batoid fishes from Korea (especially in the Yellow Sea), and also maybe in northern Japanese and northwestern Pacific waters. Okamejei kenojei is largely taken as commercial target species in South Korea, all year except in midsummer.

This species is captured as bycatch in gillnet fisheries, bottom trawl and coastal set nets in Japan and China, and in bottom trawl in Taiwan. Although it is not a target species in these areas, it is retained and utilised. In Taiwan, Province of China, and China, it is used for fishmeal (Y. Wang pers. comm.). In Japan its wings are eaten dried or processed into fishcakes (Kamaboko), (H. Ishihara pers. comm.).

Areas of this species- range, including the East China and Yellow Seas have been intensively exploited during past decades (NOAA 2004ab). No species specific information is currently available on catches or temporal trends. Total Japanese landings of skates and rays declined during 1947-1995 (from 18,000 t per year to ~4,000 t per year), mainly due to a decrease in catch in the East China Sea. This catch corresponds to small size Okamejei species and may be due to overfishing of these skates in the East China Sea (Ishihara et al. 2002).

Conservation Actions [top]

Conservation Actions: There are no specific conservation measures in place at this time. Species-specific monitoring is required to determine and monitor population trends.

Citation: Ishihaha, H., Wang, Y., Tanaka, S. & Nakaya, K. 2009. Okamejei kenojei. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 24 October 2014.
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