|En - Narrownose smooth-hound, Fr - Émissole gatuso, Sp - Gatuso.|
3Alpha Code: SDP Taxonomic Code: 1080400712|
|Scientific Name with Original Description|
|Mustelus schmitti Springer, 1940, Proc. U.S. Natl. Mus. 86(3058): 465. Holotype: U.S. National Museum of Natural History, USNM 107740, 742 mm adult male. Type Locality: Off coast of Uruguay.|
Body fairly slender. Head short, prepectoral length 17 to 21% of total length. Snout moderately long and bluntly angular in lateral view, preoral snout 5.7 to 7.4% of total length, preorbital snout 5.8 to 7.8% of total length. Internarial space very narrow, 1.8 to 2.4% of total length. Eyes fairly large, eye length 2.0 to 3.1 times in preorbital snout and 2.1 to 3.5% of total length. Interorbital space fairly narrow, 4.3 to 5.3% of total length. Mouth short, subequal to eye length and 2.3 to 3.2% of total length. Upper labial furrows considerably longer than lowers and 1.8 to 2.6% of total length.
Teeth molariform and asymmetric, with cusp low and rounded. Buccopharyngial denticles not known. Crowns of lateral trunk denticles lanceolate, with longitudinal ridges extending at least half their length.
Pectoral fins fairly small, length of anterior margins 12 to 16% of total length, width of posterior margin 8.6 to 13% of total length. Pelvic fins small, anterior margin length 6.7 to 8.7% of total length. Interdorsal space 17 to 23% of total length. Trailing edges of dorsal fins naked, with a band of bare ceratotrichia. First dorsal broadly triangular, with posteroventrally sloping posterior margin, midbase closer to pelvic bases than pectorals. Anal height 2.5 to 3.5% of total length. Anal-caudal space slightly greater or subequal to second dorsal height and 5.8 to 7.8% of total length. Ventral caudal lobe not expanded and falcate in adults.
Cranium, hyomandibulare, scapulocoracoids not hypercalcified in adults. Palatoquadrates not subdivided. Monospondylous precaudal centra 36 to 39, diplospondylous precaudal centra 45 to 54, precaudal centra 82 to 88.
Colour gray above, light below, often with numerous white spots but no dark spots or dark bars. Development ovoviviparous. Size moderate, adults 48 to 74 cm.
|fieldmarks: A white-spotted Mustelus with a very narrow internarial space and dorsal fins with naked ceratotrichia on margins|
|Habitat and Biology|
|Habitat and Biology: A common bottom-dwelling shark of the continental shelf of Atlantic South America, at depths of 60 to 195 m.|
Ovoviviparous, without a placenta, 2 to 7 pups per litter.
Eats crabs and probably other crustacea, and presumably small fishes.
|Size: Maximum at least 74 cm; males maturing at about 48 cm and females at about 55 to 60 cm; size at birth 26 cm.|
|Interest to Fisheries|
|Interest to Fisheries: An important fishery for this species exists off Argentina since 1960. Catches reported to FAO have never been lower than 4,500 t since 1967 and reached a peak of 13,597 t in 1988. In the last five years reported (1992-96), the catches have stabilized around 10,000 t per year. The total catch reported for this species to FAO for 1999 was 12 274 t. The countries with the largest catches were Argentina (9 062 t) and Uruguay (3 212 t).|
The species is also regularly caught off Uruguay, and utilized there for meat (marketed fresh and dried salted for human consumption) and oil.
Impact of fisheries This small shark has been the subject of important fisheries throughout its range (southern Brazil, Uruguay and Argentina). Off southern Brazil, it was caught by bottom trawlers but decreasing catches made the fishery switch to gillnets and longlines ("Shark longlining") (Vooren per. comm. 1991). Several Brazilian reports (cited by Anon. 1997) indicate that the joint tope-narrownose smoothhound CPUE from trawlers decreased to 25% of 1987 levels by the mid-1990s, and that the population abundance of narrownose smoothhound had decreased at a rate of 10% per year since 1980. According to Chiaramonte (in press), this species is very popular for human consumption in Argentina where its landings (mostly from multispecific trawl fisheries) exceeded 9,000 t in 1975, remained around 5,000 t/y until the early 1990s but have doubled in 5 years from some 5,000 t in 1992 to 10,300 t in 1996. The estimation of the current abundance trend of this stock is not known. However, gross estimates based on the Gulland method suggest that the MSY for this species in Argentina might be around 19,000 t (Otero et al. 1982, cited in Chiaramonte and Corcuera 1995). Some northern Argentina pupping and nursery areas for the narrownose smoothhound are under threat of environmental degradation due to among other things, the establishment of industrial parks (Chiaramonte in press).
Conservation Status : Conservation status Although smoothhounds tend to have a relatively high intrinsic rebound potential (Smith et al. 1998), given the restricted distribution of the narrownose smoothhound and the apparent decreasing abundance of some of the stocks due to unrestricted exploitation the conservation of this species should be a cause for concern.
|Remarks: A distinctive species, not close to any of the other white-spotted ovoviviparous smooth-hounds.|
Threat to humans: Dangerousness Harmless to people.
Bigelow & Schroeder, (1940, 1948)