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Squalus megalops
– Data Deficient
Taxonomy
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Kingdom:
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ANIMALIA
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Phylum:
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CHORDATA
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Class:
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CHONDRICHTHYES
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Order:
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SQUALIFORMES
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Family:
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SQUALIDAE
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Scientific Name:
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Squalus megalops
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Species Authority:
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(Macleay, 1881)
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Common Name/s:
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| English | — | COSMOPOLITAN SPURDOG, PIKED SPURDOG, SHORTNOSE SPURDOG |
| French | — | AIGUILLAT NEZ COURT |
| Spanish | — | GALLUDO NATO |
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Taxonomic Notes:
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Synonym = Squalus tasmaniensis Rivero 1936 – local synonymy.
There are unresolved taxonomic problems with this species. Dogfishes referred to in the literature as Squalus megalops appear to belong to a complex of similar species rather than a single, very wide-ranging species that spans the Eastern Atlantic and Indo-West Pacific. Compagno (in prep) reports that Last and Stevens (1994) statement: that typical Squalus megalops is an Australian endemic, may be correct, but their account does not suggest any obvious differences between the typical Australian S. megalops and the very similar nominal S. megalops from off southern Africa, the Eastern North Atlantic, or the Western North Pacific. The typical Australian S. megalops needs to be critically compared with nominal S. megalops from elsewhere, but for the moment, pending a revision of S. megalops complex worldwide the various nominal records of S. megalops and likely synonyms are considered as a single species. It is likely that as with certain other dogfish there are discrete populations, stocks or subpopulations of S. megalops, with differences in size at maturity and maximum size.
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Assessment Information
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Red List Category & Criteria:
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DD ver 3.1 (2001)
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Year Assessed:
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2003
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Assessor/s:
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Cavanagh, R.D. & Lisney, T.J. (SSG Australia & Oceania Regional Workshop, March 2003)
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Evaluator/s:
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Walker, T.I., McAuley, R. (Shark Red List Authority) & Graham, K.
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Justification:
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A common to abundant dogfish of temperate and tropical seas, this species is of considerable interest to fisheries. It is taken in significant quantities in bottom trawls and also caught with lines and mesh nets. Squalus megalops is one of the most abundant chondrichthyan species on the outer continental shelf and upper slope of southern Australia. Its distribution includes some heavily fished areas, for example, off southeast Australia, although significant declines have not been documented to date. It is a minor component of the demersal gillnet fisheries through Bass Strait, off South Australia and Western Australia. However, S. megalops is too small to be readily captured by gillnets, particularly the 6 to 6½-inch mesh of shark nets, and there has been no detectable changes in catch rates of this species by commercial shark gillnets in Bass Strait since the 1970s. There are large regions around southern Australia where S. megalops is not greatly impacted by fishing, including a large area off the northern west coast which is closed to shark fishing. Consequently, the species is assessed as Least Concern in Australia, but the situation should be monitored because there are recent indications that fishing pressure may be affecting the local abundance of the species in some areas e.g., off Ulladulla, New South Wales. It should be noted that although currently considered a wide-ranging single species, S. megalops, as assessed here, may in fact be an Australian endemic pending further taxonomic studies. Due to taxonomic uncertainty, the global assessment is Data Deficient, pending further study.
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Geographic Range
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Range Description:
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Eastern Atlantic and Mediterranean (Alboran Sea and western Mediterranean), western Indian Ocean, western Pacific (Sea of Japan and Yellow Sea south to Gulf of Tonkin), southern Australia, New Caledonia and New Hebrides.
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Countries:
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Native:
Angola; Australia (South Australia, Tasmania, Victoria); China; Congo; Congo, The Democratic Republic of the; Gabon; Guinea; Japan; Korea, Democratic People's Republic of; Korea, Republic of; Madagascar; Mauritania; Mauritius; Morocco; Mozambique; Namibia; New Caledonia; Portugal; South Africa (Eastern Cape Province, KwaZulu-Natal, Northern Cape Province, Western Cape Province); Spain; Taiwan, Province of China; Viet Nam; Western Sahara
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FAO Marine Fishing Areas:
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Native:
Atlantic-northeast; Atlantic-southeast; Indian Ocean-eastern; Indian Ocean-western; Mediterranean and Black Sea; Pacific-northwest; Pacific-western central
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Population
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Population Trend:
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Habitat and Ecology
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Habitat and Ecology:
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A common to abundant small dogfish of temperate and tropical seas, found on the inner and outer continental shelves and upper slopes generally on or near the bottom at depths from close inshore down to 732 m. Much of the biological information is from South African specimens. Off South Africa newborn young were found to be pelagic on pupping grounds on the outer continental shelves on the Agulhas Bank at about 157 to 158 m through sampling with an Engels pelagic trawl hauled by the RV Africana, and were abundantly collected along with a few adults (mostly males) from near the bottom to the surface. This is a social shark that often forms large, dense schools where it occurs. On the east coast of South Africa some sexual segregation may occur, with breeding females more southerly in distribution. Ovoviviparous (aplacental viviparous), with number of young per litter 1-6 and generally two or three. There may be a lack of birth seasonality with no obvious peaks in fetal size during the year. The gestation period is uncertain although it has been estimated as two years. Adult females are apparently continuously reproductive, without a gap between pregnancies. This shark eats a variety of bony fishes, and more rarely elasmobranchs. Invertebrate prey includes a variety of crustaceans, mollusks, cephalopods, brittle stars and especially bristleworms (Polychaeta). which are common prey items. Maximum total length is about 77 cm, with most smaller than 65 cm. Term fetuses about 20 to 25 cm long, size at birth about 23 to 25 cm, freeliving young with yolk scars 23 to 28 cm; males maturing at about 34 to 51 cm, females mature at 37 to 62 cm. Age at maturity has been estimated at 22 years for females and 15 years for males in the South Africa population (Watson and Smale 1999).
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System:
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Marine
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List of Habitats:
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| 9.1 | Marine Neritic - Pelagic |
| 10.1 | Marine Oceanic - Epipelagic (0-200m) |
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Threats
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Threats:
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This species is of considerable interest to fisheries and is taken in considerable quantities in demersal trawls but also on lines and nets. It is commonly caught as bycatch of the trawl fishery off southern Africa but is largely discarded.
In Australia S. megalops was shown to be a major component of the catch by a fishery independent trawl survey (Graham et al. 2001) between the years 1976 to 1977 and 1996 to 1997 between the Sydney area (central New South Wales (NSW)) and the Eden-Gabo I. area (southern NSW/northern Victoria). However, this species did not follow the general pattern of decline shown by other species of deepwater dogfish, and it appears that the present level of trawling is not adversely affecting S. megalops. This could be due to recruitment from the lightly fished outer shelf areas helping to maintain their overall biomass. Despite this, the situation needs to be monitored as there are indications that the relatively heavy fishing pressure off Ulladulla (NSW) is in fact beginning to affect local abundance of this species (although this is unlikely to markedly affect the entire population). Because of its relatively small size, S. megalops has historically not been targeted by trawlers off south-eastern Australia; but as catch rates of more traditional species decline, greater exploitation of this species is likely to occur. Along the south coast of Australia, trawl grounds are mainly away from the areas inhabited by this species, and selectivity data indicates that comparatively low numbers are captured in the commercial shark gillnets of 6-6.5-inch mesh-size. There is no detectable change in catch rates with 6-inch mesh-size between 1973 to 1976 and 1998 to 2001 in Bass Strait (Walker et al. in press).
S. megalops is a very minor component of the temperate Western Australia demersal gillnet fishery (probably less than one tonne/year) and possibly the Commonwealth managed trawl fisheries. The gillnet fishery only operates to the inshore limit of the species' range (i.e., to around 100 m depth) and there is a large area off the northern west coast that is closed to shark fishing. Catches are hard to ascertain as dogfish are generally not retained and not identified to species level in either fishery. There is no evidence to suggest a population decline (R. McAuley, WA Fisheries. pers.comm. April 2003).
It is utilized for human consumption in Australia being sold as fresh fillets. Significant quantities of ‘greeneye’ dogfish, comprising about 80% S. megalops, are sold annually through the Sydney Fish Market but sales have declined in recent years (Daley et al. 2002). Sales of greeneye dogfish declined from about 150 tonnes in 1992 to about 50 tonnes in 1999. Quantities sold in other Australian markets are small.
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List of Threats:
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| 4.1.1.1 | Accidental mortality - Bycatch - Fisheries-related - Hooking (ongoing) |
| 4.1.1.2 | Accidental mortality - Bycatch - Fisheries-related - Netting (ongoing) |
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Conservation Actions
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Conservation Actions:
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There are currently no conservation measures in place for this species.
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List of Conservation Actions:
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| 0 | No conservation actions (in place) |
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Bibliography
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Bibliography:
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Compagno, L.J.V. In prep. a. Sharks of the World. An annotated and illustrated catalogue of the shark species known to date. Volume 1. (Hexanchiformes, Squaliformes, Squatiniformes and Pristiophoriformes). FAO Species Catalogue for Fisheries Purposes No. 1, Vol.1. FAO, Rome. Daley, R., Stevens, J. and Graham, K. 2002. Catch analysis and productivity of the deepwater dogfish resource in southern Australia. Report by CSIRO Marine Research and NSW Fisheries to the Fisheries Research and Development Corporation. FRDC Project 1998/108. Graham, K.J., Andrew, N.L. and Hodgson, K.E. 2001. Changes in the relative abundances of sharks and rays on Australian South East Fishery trawl grounds after twenty years of fishing. Journal of Marine and Freshwater Research 52: 549-561. Last, P.R. and Stevens, J.D. 1994. Sharks and Rays of Australia. CSIRO, Australia. Shark Specialist Group. For more information, see the Specialist Group website. Walker, T.I., Hudson, R.J. and Gason, A.S. In press. Catch evaluation of target, byproduct, and bycatch species taken by gillnets and longlines in the shark fishery of south-eastern Australia. In: Proceedings of North Atlantic Fisheries Organisation Symposium. Elasmobranch Fisheries: Managing for Sustainable Use and Biodiversity Conservation. 11–13 September 2002. Santiago de Compostela, Spain. Journal of Northwest Atlantic Fishery Science Watson, G. and Smale, M.J. 1999. Age and growth of the shortnose spiny dogfish Squalus megalops from the Agulhas Bank, South Africa. South African Journal of Marine Science 21: 9-18.
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