Isistius plutodus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	SQUALIFORMES	DALATIIDAE

Scientific Name:

Isistius plutodus

Species Authority:

Garrick & Springer, 1964

Common Name/s:

English	–	Bigtooth Cookiecutter, Gulf Dogfish, Largetooth Cookiecutter Shark, Longtooth Cookiecutter Shark
French	–	Squalelet Dentu
Spanish	–	Tollo Cigarro Dentón

Assessment Information [top]

Red List Category & Criteria:	Least Concern ver 3.1
Year Assessed:	2006
Assessor/s	Kyne, P.M., Gerber, L. & Sherrill-Mix, S.A.
Evaluator/s:	Heupel, M.R., Simpfendorfer, C.A. & Cavanagh, R.D. (Shark Red List Authority)
Justification: A rare epibenthic and epipelagic cookiecutter shark known from 10 specimens. Possibly circumglobal but at present recorded from scattered locations in the Pacific and Atlantic with all specimens collected close to land (in contrast to its congener Isistius brasiliensis). Largest recorded specimen just over 42 cm total length, but very little known of the biology of this facultative ectoparasite. Probably an irregular bycatch of trawl (benthic and pelagic) and longline fisheries (taken by hook or attached to its captured prey). Although little is known about this species it is probably widely distributed with no significant threats apparent and is thus assessed as Least Concern.

Geographic Range [top]

Range Description:	Possibly circumglobal, but at present known from scattered locations in the Pacific and Atlantic (Zidowitz et al. 2004, Compagno in prep. a.).
Countries:	Native: Australia (New South Wales); Brazil; Japan; Portugal (Azores); United States (Alabama); Western Sahara
FAO Marine Fishing Areas:	Native: Atlantic – western central; Atlantic – northeast; Atlantic – southwest; Atlantic – eastern central; Pacific – northwest; Pacific – southwest

Population [top]

Population:	This species is rarely encountered compared to Isistius brasiliensis (the cookiecutter shark). Compagno (in prep. a.) suggests that this may be due to more localized or limited distribution of I. plutodus, its occurrence in deeper water or its lower abundance.
Population Trend:	Unknown

Habitat and Ecology [top]

Habitat and Ecology:	Little information available on the species’ biology as it is presently known only from 10 specimens. Epibenthic (~100 m depth over the continental shelf) and epipelagic (depths of 60 to 120 m over continental slopes with bottom depths of 815-2,060m; and, 200m over the Riu-Kyu Trench with bottom depth of 6,440 m) with all known specimens collected close to land (Zidowitz et al. 2004, Compagno in prep. a). Suggested to be a weaker, less active swimmer than I. brasiliensis (Compagno in prep. a). This species is a facultative ectoparasite, like I. brasiliensis, but with a probable different biting/cutting action (Compagno in prep. a). Life history parameters Age at maturity (years): Unknown. Size at maturity (total length cm): Unknown. Longevity (years): Unknown. Maximum size (total length): At least 42 cm TL (Garrick and Springer 1964, Zidowitz et al. 2004, Compagno in prep. a.).. Size at birth (cm): Unknown. Average reproductive age (years): Unknown. Gestation time (months): Unknown. Reproductive periodicity: Unknown. Average annual fecundity or litter size: Unknown. Annual rate of population increase: Unknown. Natural mortality: Unknown.
Systems:	Marine

Habitat and Ecology:

Little information available on the species’ biology as it is presently known only from 10 specimens. Epibenthic (~100 m depth over the continental shelf) and epipelagic (depths of 60 to 120 m over continental slopes with bottom depths of 815-2,060m; and, 200m over the Riu-Kyu Trench with bottom depth of 6,440 m) with all known specimens collected close to land (Zidowitz et al. 2004, Compagno in prep. a).

Suggested to be a weaker, less active swimmer than I. brasiliensis (Compagno in prep. a). This species is a facultative ectoparasite, like I. brasiliensis, but with a probable different biting/cutting action (Compagno in prep. a).

Life history parameters
Age at maturity (years): Unknown.
Size at maturity (total length cm): Unknown.
Longevity (years): Unknown.
Maximum size (total length): At least 42 cm TL (Garrick and Springer 1964, Zidowitz et al. 2004, Compagno in prep. a.)..
Size at birth (cm): Unknown.
Average reproductive age (years): Unknown.
Gestation time (months): Unknown.
Reproductive periodicity: Unknown.
Average annual fecundity or litter size: Unknown.
Annual rate of population increase: Unknown.
Natural mortality: Unknown.

Systems:

Marine

Threats [top]

Major Threat(s):	Rarely caught in trawl (pelagic and benthic) and longline fisheries. The Australian specimen was probably taken by otter trawl targeting prawns (not known if taken on/near the bottom or in midwater) (McGrouther 2001). The Azores specimen was taken by pelagic trawl (Zidowitz et al. 2004) and the Brazilian specimens were collected from longline fisheries operating out of Santos in the south of the country. One specimen was retrieved attached to a hooked blue shark Prionace glauca (Sadowsky et al. 1988, Amorin et al. 1998).

Major Threat(s):

Rarely caught in trawl (pelagic and benthic) and longline fisheries. The Australian specimen was probably taken by otter trawl targeting prawns (not known if taken on/near the bottom or in midwater) (McGrouther 2001). The Azores specimen was taken by pelagic trawl (Zidowitz et al. 2004) and the Brazilian specimens were collected from longline fisheries operating out of Santos in the south of the country. One specimen was retrieved attached to a hooked blue shark Prionace glauca (Sadowsky et al. 1988, Amorin et al. 1998).

Conservation Actions [top]

Conservation Actions:	Further specimens are required to better define distribution and obtain information on biology.

Conservation Actions:

Further specimens are required to better define distribution and obtain information on biology.

Citation:	Kyne, P.M., Gerber, L. & Sherrill-Mix, S.A. 2006. Isistius plutodus. In: IUCN 2008. 2008 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 04 December 2008.
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