The Japanese spurdog (Squalus japonicus) is a dogfish, a member of the family Squalidae. It is found in the western Pacific Ocean – southeastern Japan and the East China Sea,[2] including the Republic of Korea, the Philippines, and the Arafura Sea.[3] It occurs in temperate and tropical waters along the continental shelf and slopes[4] and primarily feeds on teleost fish and squid.[2] It is caught as bycatch in commercial fishing, which has caused populations to decline.[5]
Japanese spurdog | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Order: | Squaliformes |
Family: | Squalidae |
Genus: | Squalus |
Species: | S. japonicus |
Binomial name | |
Squalus japonicus Ishikawa, 1908 | |
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Range of the Japanese spurdog (in blue) |
Description
Males measure 50 to 70 cm (19.7 to 27.6 in) long in adulthood, while females measure 56 to 80 cm (22 to 31.5 in) long.[5] Females are also higher in weight than males.[2] They have 25 to 27 teeth on their upper jaw and 20 to 24 teeth on their lower jaw.[4]
Distribution and habitat
The Japanese spurdog is found in the Pacific Ocean, in southeast Japan, China, North Korea, South Korea, and Taiwan.[5][4] Additionally, there is one record of S. japonicus being caught in a trawl net in the Arafura Sea, between Australia and Western New Guinea.[3] It is a demersal species, found on the continental shelf and upper slope[4] at depths of 52 to 400 m (170.6 to 1312 ft).[5]
Reproduction
They are viviparous, giving birth to between 2 and 8 pups each litter.[4] The pups are 19 to 30 cm (7.5 to 11.8 in) long at birth.[4] Gestation is 11 to 12 months[5] and they reproduce annually.[4] A study in the East China Sea found an equal sex ratio of both embryos and adults.[2]
Conservation
The Japanese spurdog is listed on the IUCN Red List as Endangered.[5] Populations in Japan have been stable since 1983, but shark abundance elsewhere in its range has been in decline since the middle of the twentieth century.[5] It is believed that S. japonicus abundance has declined in those areas as well.[5]
Its major threat is commercial fishing. Though not a commercial product itself, it is caught as bycatch in demersal fishing and used for meat or fish meal.[4]
References
External links
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