Schroederichthys bivius

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

View Printer Friendly

Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	CHONDRICHTHYES	CARCHARHINIFORMES	SCYLIORHINIDAE

Scientific Name:

Schroederichthys bivius

Species Authority:

(Smith, in Müller & Henle, 1838)

Common Name/s:

English

–

Narrowmouth Catshark, Narrowmouth Catshark

Synonym/s:

Scyllium bivium Müller & Henle, 1838

Assessment Information [top]

Red List Category & Criteria:

Data Deficient ver 3.1

Year Assessed:

2005

Assessor/s

Chiaramonte, G.E.

Evaluator/s:

Musick, J.A. & Fowler, S.L. (Shark Red List Authority)

Justification:
The Narrowmouth Catshark, or ‘Pintarroja’, (Schroederichthys bivius) is an endemic species of the southwest Atlantic and southeast Pacific continental shelf, from Brazil to Chile, found at depths of 10–359 m. Good data are available on the biology of this poorly known, albeit moderately common inshore and offshore shark, but there is inadequate information on the possible impacts of habitat degradation and fisheries on its populations.

History:

2000

–

Data Deficient

Geographic Range [top]

Range Description:	The Narrowmouth Catshark is an endemic shark from the coasts of South America within the Magellanic province (Norman 1937). It originates from the Pacific basin (Krefft 1968), and inhabits the Southwest Atlantic from Brazil (Amorim et al. 1995) to the Beagle Channel (Lloris and Rucabado 1991, Matallanas et al. 1993) and the Southeast Pacific to north of Chile (Compagno 1984b). It occurs from the surface to 179m in the Atlantic Ocean (Bellisio et al. 1979, Menni et al. 1979) and reaches 359 m in the Pacific Ocean (Ojeda 1983).
Countries:	Native: Argentina; Brazil; Chile; Uruguay
FAO Marine Fishing Areas:	Native: Atlantic – southwest; Pacific – southeast

Population [top]

Population Trend:	Unknown

Population Trend:

Unknown

Habitat and Ecology [top]

Habitat and Ecology:	The Narrowmouth Catshark shows an unusual secondary sexual dimorphism, with longer males than females and females heavier than males (Menni et al. 1979, Menni 1986). It reaches a maximum size of about 80 cm total length (TL) in males and 70 cm in females (Menni et al. 1979, Menni 1986). Males reach sexual maturity at 53 cm TL and are all sexually mature at 66.5 cm TL; females reach sexual maturity at 40 cm TL and are all sexually mature at 45 cm TL (Gosztonyi 1973, Menni et al. 1979, Menni 1986). It is an oviparous species, probably laying one egg at a time per oviduct (Gosztonyi 1973, Menni et al. 1979, Compagno 1984b, Menni 1986). Menni et al. (1979) reported females carrying egg capsules in autumn (April– May) and spring (August–September). The egg cases are anchored onto the seabed in estuaries and other sheltered areas. Menni et al. (1979) pointed out that females from 42.2– 44.2 cm TL showed neither a nidamental gland nor widening of the uterus and oocytes measured under 2 mm. From lengths of 45–51.2 cm TL, oocytes of 1–15 mm were observed. Nidamental gland width was 3–22 mm and a wider uterus (22×3 mm to 45×7 mm) was observed in 66% of individuals. From 51.2–62.5 cm TL, egg capsules were absent in 49.1% of the sample, 3.8% showed a flaccid and vascularised uterus (probably recently emptied), 15% of the sample had oviductal eggs and 32% carried egg capsules, always one in each organ. The same authors reported that when maturity begins, the right ovary develops, while the left one goes into regression. Gosztonyi (1973) shows that both the mouth and teeth shape are sexually dimorphic in this species and that this change starts in both sexes at 30 cm TL. Teeth in adult males are unicuspidate and twice as high as the tricuspidate teeth of females of similar size. Although Menni et al. (1979) and Menni (1986) pointed out some sexual segregation, with more numerous females in the shallow stratum (below 100 m) while large numbers of males occur between 100–130 m, Matallanas et al. (1993) did not find any segregation with depth in their sample. The diet of this shark, according to Matallanas et al. (1993), in the Beagle Channel during summer is predominantly monophagous, consisting mainly of Munida subrugosa (Crustacea: Decapoda). The presence of other incidental prey was higher in males than in females. For example, the frequency of teleosts in the diet was higher in males of over 40 cm TL, but not significantly. In comparison, analysis of data from two cruises on the Southwest Atlantic continental shelf indicated that the diet was less selective than in the Beagle Channel (although the methodology of analysis was different and the results not strictly comparable). This variation can be explained by a change in predation behaviour in different habitats: leptobenthic behaviour on the continental shelves, as defined by Compagno (1990a) for Schroederychthys species and a crab-eating littoral behaviour in the more restricted habitat of the Beagle Channel, typical of the smoothhounds and related species (Compagno 1990a).
Systems:	Marine

Habitat and Ecology:

The Narrowmouth Catshark shows an unusual secondary sexual dimorphism, with longer males than females and females heavier than males (Menni et al. 1979, Menni 1986). It reaches a maximum size of about 80 cm total length (TL) in males and 70 cm in females (Menni et al. 1979, Menni 1986). Males reach sexual maturity at 53 cm TL and are all sexually mature at 66.5 cm TL; females reach sexual maturity at 40 cm TL and are all sexually mature at 45 cm TL (Gosztonyi 1973, Menni et al. 1979, Menni 1986).

It is an oviparous species, probably laying one egg at a time per oviduct (Gosztonyi 1973, Menni et al. 1979, Compagno 1984b, Menni 1986). Menni et al. (1979) reported females carrying egg capsules in autumn (April– May) and spring (August–September). The egg cases are anchored onto the seabed in estuaries and other sheltered areas.

Menni et al. (1979) pointed out that females from 42.2– 44.2 cm TL showed neither a nidamental gland nor widening of the uterus and oocytes measured under 2 mm. From lengths of 45–51.2 cm TL, oocytes of 1–15 mm were observed. Nidamental gland width was 3–22 mm and a wider uterus (22×3 mm to 45×7 mm) was observed in 66% of individuals. From 51.2–62.5 cm TL, egg capsules were absent in 49.1% of the sample, 3.8% showed a flaccid and vascularised uterus (probably recently emptied), 15% of the sample had oviductal eggs and 32% carried egg capsules, always one in each organ. The same authors reported that when maturity begins, the right ovary develops, while the left one goes into regression.

Gosztonyi (1973) shows that both the mouth and teeth shape are sexually dimorphic in this species and that this change starts in both sexes at 30 cm TL. Teeth in adult males are unicuspidate and twice as high as the tricuspidate teeth of females of similar size. Although Menni et al. (1979) and Menni (1986) pointed out some sexual segregation, with more numerous females in the shallow stratum (below 100 m) while large numbers of males occur between 100–130 m, Matallanas et al. (1993) did not find any segregation with depth in their sample.

The diet of this shark, according to Matallanas et al. (1993), in the Beagle Channel during summer is predominantly monophagous, consisting mainly of Munida subrugosa (Crustacea: Decapoda). The presence of other incidental prey was higher in males than in females. For example, the frequency of teleosts in the diet was higher in males of over 40 cm TL, but not significantly. In comparison, analysis of data from two cruises on the Southwest Atlantic continental shelf indicated that the diet was less selective than in the Beagle Channel (although the methodology of analysis was different and the results not strictly comparable). This variation can be explained by a change in predation behaviour in different habitats: leptobenthic behaviour on the continental shelves, as defined by Compagno (1990a) for Schroederychthys species and a crab-eating littoral behaviour in the more restricted habitat of the Beagle Channel, typical of the smoothhounds and related species (Compagno 1990a).

Systems:

Marine

Threats [top]

Major Threat(s):	The Narrowmouth Catshark uses estuaries and other sheltered areas to lay their egg cases and as nurseries. Egg cases have so far only been recovered from the estuary of Ria Deseado (Gosztonyi 1973). There have been no reports made of egg cases from continental shelves. Local sport and commercial fishermen have not caught any pintarroja in the above estuary in the last eight years, although it was formerly very common there. The marked increase in the use of Patagonian natural harbours by fishing and oil vessels over the last 15 years, with consequent disturbance, oil and noise pollution in these estuaries and bays, has not been assessed in terms of its impact on shark breeding grounds. However, acoustic pollution in these inlets could be one reason for the loss of this reproductive habitat. For example, a study of the association between noise levels in the Ria Deseado and the behaviour of Commerson’s Dolphin (Cephalorhynchus commersonii), has demonstrated an association between rising noise levels and escape behaviour (M. Iniguez pers. comm.). However, other sharks, such as Narrownose Smoothhound (Mustelus schmitti) and probably the Broadnose Sevengill Shark (Notorynchus cepedianus) (Chiaramonte and Pettovello 2000), also use the estuaries and sheltered areas in Patagonia as nursery grounds, and these species have apparently not shown any decline in connection with human use of the areas. The species is taken as bycatch by bottom-trawlers and outriggers in Patagonian waters, but it has not been possible to estimate the scale of capture. This species may also be taken by directed commercial fisheries and possibly exported (Chiaramonte 1996).

Major Threat(s):

The Narrowmouth Catshark uses estuaries and other sheltered areas to lay their egg cases and as nurseries. Egg cases have so far only been recovered from the estuary of Ria Deseado (Gosztonyi 1973). There have been no reports made of egg cases from continental shelves. Local sport and commercial fishermen have not caught any pintarroja in the above estuary in the last eight years, although it was formerly very common there.

The marked increase in the use of Patagonian natural harbours by fishing and oil vessels over the last 15 years, with consequent disturbance, oil and noise pollution in these estuaries and bays, has not been assessed in terms of its impact on shark breeding grounds. However, acoustic pollution in these inlets could be one reason for the loss of this reproductive habitat. For example, a study of the association between noise levels in the Ria Deseado and the behaviour of Commerson’s Dolphin (Cephalorhynchus commersonii), has demonstrated an association between rising noise levels and escape behaviour (M. Iniguez pers. comm.). However, other sharks, such as Narrownose Smoothhound (Mustelus schmitti) and probably the Broadnose Sevengill Shark (Notorynchus cepedianus) (Chiaramonte and Pettovello 2000), also use the estuaries and sheltered areas in Patagonia as nursery grounds, and these species have apparently not shown any decline in connection with human use of the areas.

The species is taken as bycatch by bottom-trawlers and outriggers in Patagonian waters, but it has not been possible to estimate the scale of capture. This species may also be taken by directed commercial fisheries and possibly exported (Chiaramonte 1996).

Conservation Actions [top]

Conservation Actions:	Captures of this species in fisheries are not recorded and there are no conservation or management initiatives underway.

Conservation Actions:

Captures of this species in fisheries are not recorded and there are no conservation or management initiatives underway.

Citation:	Chiaramonte, G.E. 2005. Schroederichthys bivius. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. <www.iucnredlist.org>. Downloaded on 09 February 2010.
Disclaimer:	To make use of this information, please check the <Terms of Use>.
Feedback:	If you see any errors or have any questions or suggestions on what is shown on this page, please fill in the feedback form so that we can correct or extend the information provided