Bythaelurus dawsoni

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	CARCHARHINIFORMES	SCYLIORHINIDAE

Scientific Name:

Bythaelurus dawsoni

Species Authority:

Springer 1971

Common Name/s:

English

–

Dawson's Cat Shark, New Zealand Catshark

Synonym/s:

Halaelurus dawsoni Springer 1971

Taxonomic Notes:

The species was described in 1971 from nine specimens collected from southern New Zealand. However, the collection locality of the holotype and four paratypes was incorrectly reported as 44°32.5' S, 166°41' E which is in depths of several thousand metres; it should be 46°32.5' S, 166°41' E. There have been no taxonomic studies of this species since its original description. Originally placed under genus Halaelurus and subgenus Bythaelurus. Bythaelurus is now elevated to generic level (P. Kyne in litt. 2004).

Assessment Information [top]

Red List Category & Criteria:

Data Deficient ver 3.1

Year Published:

2003

Assessor/s:

Francis, M.P. (SSG Australia & Oceania Regional Workshop, March 2003)

Reviewer/s:

Fowler, S. & Cavanagh, R.D. (Shark Red List Authority)

Justification:
There is no information on the population abundance or catches of this New Zealand endemic. It has a small distributional range (most of the population occurs in an area of about 722,000 km²) and it is uncommon. Research trawl tows in the habitat area usually catch no sharks, and tows that do catch them usually take only a few individuals. The only known threat is fishing by deep-water bottom trawlers, but the small size of the shark probably ensures a large proportion escape through the codend meshes, which are a minimum of 100 mm over much of the habitat range.

History:

2003

–

Data Deficient (IUCN 2003)

Geographic Range [top]

Range Description:	Limited to New Zealand between 38°S and 54°S, but most records are from south-eastern New Zealand (Chatham Rise and Campbell Plateau) at 43 to 54°S.
Countries:	Native: New Zealand
FAO Marine Fishing Areas:	Native: Pacific – southwest
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population Trend:	Unknown

Population Trend:

Unknown

Habitat and Ecology [top]

Habitat and Ecology:	Occurs over a depth range of 50 to 790 m, but is most abundant in 300 to 700 m. All known records have been obtained by bottom trawlers over soft sediment, however, it is possible that the species also occurs over foul, untrawlable seabed. Feeds on crustaceans. Males mature at 35 to 36 cm total length (TL) and females at 37 to 38 cm TL (M.P. Francis, unpubl. data). Maximum known length 41.5 cm TL. Males and females grow to similar maximum lengths. Females produce thick-shelled egg cases, two at a time, that are presumably deposited on the seabed. Size at hatching is unknown but smallest observed free-living individual 11.3 cm TL.
Systems:	Marine

Habitat and Ecology:

Occurs over a depth range of 50 to 790 m, but is most abundant in 300 to 700 m. All known records have been obtained by bottom trawlers over soft sediment, however, it is possible that the species also occurs over foul, untrawlable seabed. Feeds on crustaceans.

Males mature at 35 to 36 cm total length (TL) and females at 37 to 38 cm TL (M.P. Francis, unpubl. data). Maximum known length 41.5 cm TL. Males and females grow to similar maximum lengths. Females produce thick-shelled egg cases, two at a time, that are presumably deposited on the seabed. Size at hatching is unknown but smallest observed free-living individual 11.3 cm TL.

Systems:

Marine

Threats [top]

Major Threat(s):	Probably caught occasionally as trawl bycatch, but their small size means that escapement from trawl nets would be high.

Major Threat(s):

Probably caught occasionally as trawl bycatch, but their small size means that escapement from trawl nets would be high.

Conservation Actions [top]

Conservation Actions:	None, apart from a restriction on the mesh size of trawl nets to 100 mm or greater at latitudes north of 50°S.

Conservation Actions:

None, apart from a restriction on the mesh size of trawl nets to 100 mm or greater at latitudes north of 50°S.

Citation:	Francis, M.P. 2003. Bythaelurus dawsoni. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 22 May 2012.
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