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Mustelus norrisi

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES CARCHARHINIFORMES TRIAKIDAE

Scientific Name: Mustelus norrisi
Species Authority: Springer, 1939
Common Name(s):
English Narrowfin Smooth Hound
Taxonomic Notes: Preliminary morphometric analysis indicates that all characters commonly used to separate Mustelus norrisi from M. canis actually overlap and are not unique. In addition, preliminary genetic analyses suggest that M. norrisi and M. canis may be one species (Jones unpublished).

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2009
Date Assessed: 2008-12-01
Assessor(s): Jones, L.M., Kyne, P.M. & Carlisle, A.B.
Reviewer(s): Valenti, S.V. & Francis, M. (Shark Red List Authority)
Justification:
The Narrowfin Smooth Hound (Mustelus norrisi) is commonly found inshore on sandy/muddy bottoms usually at depths shallower than 55 m, but has been recorded down to 84 m. It has a patchy distribution in the western Atlantic in US waters, the Caribbean coast of South America and southern Brazil, and is apparently common where it occurs. It is believed that it is migratory in the Gulf of Mexico, moving to inshore shallower waters in the winter and offshore in the summer. Little is known of this species’ population status, although it is taken in unknown numbers in trawl fisheries in the Gulf of Mexico and possibly off the east coast of the U.S.A. Given its inshore occurrence, it is also likely to be taken in fisheries where it occurs in South America (Colombia, Venezuela and southern Brazil—all areas that receive relatively intensive coastal and shelf fishing pressure, and where declines in Mustelus species have been documented). Preliminary research is indicating that the Narrowfin Smooth Hound may not be distinct from the Dusky Smooth Hound (Mustelus canis), and on-going work should confirm its taxonomic status. For this reason it is listed as Data Deficient. However, while its taxonomic status is uncertain, and while little information is available on this species, as known it has a moderate fecundity, is targeted by small commercial fisheries throughout its range, and it occurs in waters where it is vulnerable to being caught as bycatch. All of these factors indicate that this species could be vulnerable to overexploitation (as documented in other Mustelus species in parts of its range). Further research should verify its taxonomic status, but there is a need to determine population trends and catch status where it occurs.

Geographic Range [top]

Range Description: Historically thought not to occur on the U.S. east coast, but recent examination of specimens from South Carolina suggest that M. norrisi is present in these waters.
Countries:
Native:
Brazil; Colombia; United States (Alabama, Florida, Georgia, South Carolina, Texas); Venezuela, Bolivarian Republic of
FAO Marine Fishing Areas:
Native:
Atlantic – southwest; Atlantic – western central
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: A common shark where it occurs (Compagno in prep.).
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: This shark is found on continental shelves, near the sea bottom, on sandy and mud sediments (Compagno in prep). It occurs close inshore to at least 84 m depth, although most records are shallower than 55 m (Compagno in prep). They have been observed to segregate by sex and size off Florida, and adult males are more common inshore during the winter. Apparently migratory in the Gulf of Mexico, this species moves inshore into water shallower than 55 m in the winter months and retreats into deeper water in other seasons. Males mature at 76–81 cm, and reach a size of at least 118 cm, and females mature at 76–87 cm and reach a size of at least 123 cm. Maximum recorded size is 123 cm, and size at birth is 29–37 cm. They are viviparous, with a yolk-sac placenta, and the number of young range from 7–14 per litter. They prey mainly on crabs and shrimp, but also small teleosts (Heemstra 1973, Heemstra 1997, Compagno in prep, Jones unpublished).
Systems: Marine

Threats [top]

Major Threat(s): This species is taken in unknown numbers in trawl fisheries in the U.S. Gulf of Mexico and may be taken in the commercial smooth dogfish fishery off the east coast of the U.S. Throughout its range there are small commercial fisheries for this shark, and they are often taken in fishing nets close to shore (Compagno in prep, Jones unpublished).

Given its inshore and shelf occurrence, the narrowfin smooth hound is likely taken as bycatch in coastal trawl, net and line fisheries across its South American range. Little specific information is available, but inshore fishing pressure is generally intense where the species occurs off Colombia, Venezuela and southern Brazil.

Medina (2002) conducted a study on bycatch from the shrimp trawl fishery in the La Guajira area (Colombia) with an evaluation of 20 sets in Cabo de La Vela but had limited species records. The only record of a Mustelus species was for M. norrisi with low abundance (eight specimens), biomass (10 kg) and occurrence (3.9%). It is also likely that M. norrisi is taken by longline fisheries that operate in this area. It is not known if the species is discarded or retained and utilised when taken as bycatch.

Off northeastern Venezuela, shrimp trawl fisheries began in the late 1960s, subsequently showing considerable increases in both effort and efficiency (Mendoza and Marcano 1994, Mendoza et al. 2003). By 2003 the commercial trawl fleet had increased to about 400 shrimp trawlers operating on the continental shelf (Mendoza et al. 2003). In addition, an artisanal fleet of 20,000 small vessels and about 1,000 medium and long-range vessels exists (Mendoza et al. 2003). The medium and long range fleet targets medium pelagics using pelagic longline, and snappers and groupers (Lutjanus purpureus and Epinephelus species) using hand line and demersal longline (Mendoza et al. 2003). Overall temporal trends in total reported catches for Venezuela showed a steep increase in landings through the 1980s and 1990s; from about 150,000 t/year to more than 350,000 t/year (Mendoza et al. 2003). Bycatch taken by shrimp trawlers off Venezuela was estimated at 96,000 tonnes annually and bycatch/shrimp ratios are typically between five and 15:1 in the region (Charlier 2000). Charlier (2000) indicates that, although only a small part of this catch is utilized, several species have apparently disappeared from the bycatch.

The very similar Dusky Smooth Hound (M. canis) has declined significantly in catches in fisheries in Venezuela (Cervigón and Alaclá 1999, Tavares 2005). During the 1980s the species was a common component of commercial landings from benthic longlining in the Archipiélago de Los Roques, but now catches are very low to absent (Tavares 2005). There is no reason to suspect that M. norrisi has not faced similar declines.

Coastal demersal species including smooth hounds are commercially important in Brazil, and although specific details are lacking, M. norrisi is likely captured in coastal fisheries off southern Brazil, where inshore fishing pressure is generally intense. The striped smooth hound Mustelus fasciatus is thought to be nearing extinction in southern Brazil due to intense gillnet pressure on inshore habitat (Hozbor et al. 2004). Massive declines have also been documented for that species off northern Argentina and Uruguay, while fishing continues for more abundant species (Hozbor et al. 2004). Shrimp and multi-species trawl fisheries operate off southern Brazil, and pressure on the inshore environment remains intensive. If such declines have been documented for M. fasciatus, it is likely that M. norrisi has suffered a similar fate there.

Research has shown that this species is contaminated by mercury off of Brazil and has mercury concentrations above the limit established by Brazilian legislation (0.5 mu g.g super(-1)), but not as high as found in other co-occurring piscivorous sharks (de Pinho et al. 2002).

Conservation Actions [top]

Conservation Actions: None in place. In the first instance, on-going research should determine the relationship of M. norrisi with M. canis (Jones unpubl. Data). Given its coastal occurrence and documented declines in other inshore Mustelus in areas of South America where M. norrisi occurs, there is an urgent need to determine population trends and catch status.

Citation: Jones, L.M., Kyne, P.M. & Carlisle, A.B. 2009. Mustelus norrisi. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 28 July 2014.
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