|Scientific Name:||Squatina argentina (Marini, 1930)|
Rhina argentina Marini, 1930
|Taxonomic Source(s):||Marini, T. L. 1930. Nueva especie de pez ángel Rhina argentina n. sp. . Physis 10(35): 5-7.|
|Taxonomic Notes:||There is some controversy concerning the nomenclature of angel sharks in southern Brazil. Vooren and Silva (1991) synonymized S. punctata with S. guggenheim. Soto (2001), in a checklist of sharks of Brazil, states that the reference in Vooren and Silva (1991) to the occurrence in Brazil of Squatina guggenheim Marini, 1936 is in fact a reference to Squatina punctata Marini, 1936, and that the description of Squatina occulta Vooren & Silva, 1991 is a reference to Squatina guggenheim as originally described by Marini (1936), but no evidence is presented to justify these statements. Furtado-Neto and Carr (2002), through the study of mitochondrial DNA, suggested the existence in southern Brazil of three species of the genus Squatina: S. argentina (Marini, 1930), S. guggenheim Marini, 1936 and S. occulta Vooren & Silva, 1991. Compagno (in prep.) follows the nomenclature of Soto (2001).
In acknowledgement of these issues, the IUCN SSC Shark Specialist Group has prepared assessments for all nominal Southwest Atlantic Squatina species: S. argentina, S. punctata, S. occulta and S. guggenheim. The validity and occurrence of S. argentina is generally agreed upon.
|Red List Category & Criteria:||Endangered A2b ver 3.1|
|Assessor(s):||Vooren, C.M. & Chiaramonte, G.E.|
|Reviewer(s):||Kyne, P.M., Cavanagh, R.D. & Musick, J.A. (Shark Red List Authority)|
Preface: In acknowledgment of unresolved and controversial taxonomic and nomenclatural issues, the IUCN SSC Shark Specialist Group has assessed all nominal Southwest Atlantic Squatina species, until such time as agreement is reached on these issues (see taxonomy section for further details). Assessed species are: longfin or Argentine angel shark Squatina argentina (Marini, 1930); spiny angel shark Squatina guggenheim Marini, 1936; shortfin angel shark Squatina occulta Vooren & Silva, 1991; and, angular angel shark Squatina punctata Marini, 1936. However, in the case of S. argentina, the validity and occurrence of the species is generally agreed upon.
Squatina argentina was assessed as Data Deficient globally on the 2000 Red List. It is updated here due to better information and evidence of declines for Brazil.
Squatina argentina is endemic to the Southwest Atlantic from Rio Grande do Sul, southern Brazil (32°S) through Uruguay to northern Patagonia, Argentina (43°S) on the outer shelf and upper slope generally at 120 to 320 m. The species' low reproductive potential (litter size of 7 to 11 and female breeding cycle at least biennial) together with its vulnerability to both trawl and gillnet gear make it highly susceptible to population depletion. Angel sharks are heavily fished in southern Brazil and significant declines have been documented there. Annual catches of angel shark from the southern Brazil continental shelf peaked at about 2,000 t in 1986 to 1989 and again in 1993, and then decreased to 900 t in 2003. Angel shark CPUE by otter and pair trawl on the continental shelf decreased by about 85% from 1984 to 2002. Research trawl surveys of the outer shelf in the years 1986/87 and 2001/02 confirmed that in southern Brazil the abundance of S. argentina has decreased to 15% of its original level and this is attributed to recruitment overfishing. In the trawl and gillnet fishery for the monkfish Lophius gastrophysus at the shelf edge and upper slope, S. occulta and S. argentina have been significant bycatch species, indicating that there has also been considerable pressure at the shelf edge and on the slope for S. argentina. Additionally, an angel shark bottom gillnet fishery on the outer shelf commenced around 1990 and at present large amounts of angel shark is caught this way. In Uruguay and Argentina the species is uncommon in commercial landings but its distribution and abundance have not been well studied. Due to the presence of trawl and other demersal fisheries throughout the range of the species and the documented reduction of angel shark stocks due to intensive fishing off southern Brazil, an assessment of Endangered is warranted across its Southwest Atlantic distribution. The conservation status of the species will rely heavily upon the success of a recently developed management plan for the southern Brazil gillnet monkfish fishery.
|Previously published Red List assessments:|
|Range Description:||Squatina argentina is endemic to the Southwest Atlantic occurring from 32°S (Rio Grande, Rio Grande do Sul, southern Brazil) through Uruguay to 43°S (north Patagonia, Argentina) (Cousseau 1973, Vooren and Silva 1991). Nursery areas of the species have not been found in southern Brazil and may exist further south off Uruguay and/or Argentina.|
Native:Argentina; Brazil; Uruguay
|FAO Marine Fishing Areas:|
Atlantic – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Squatina argentina appears to be the less abundant of the three angel shark species captured by fisheries off Rio Grande do Sul State (30°S to 34°S), Brazil (Perez and Warhlich 2005).|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Squatina argentina is a bottom-dwelling shark of smooth sandy and muddy grounds on the outer shelf and upper slope at depths of 120 to 320 m, at temperatures of 14 to 16°C, but has also been sporadically recorded to 50 m (Vooren and Silva 1991, Vooren 1997). |
Maximum size is 138 cm TL; size at maturity ~120 cm TL for both sexes (Silva 1996). Aplacental yolksac viviparous with two functional ovaries. Fecundity is 7 to 11 embryos per litter (Vooren and Silva 1991), with most females carrying 9 or 10 young. The breeding cycle of the female lasts at least two years.
The nocturnal habits of angel sharks render them vulnerable to bottom gillnets, and increases in captures during the 1990s are attributed to the introduction of this gear on the shelf and slope off southern Brazil at that time. Gillnets were reported as six times more effective at catching angel sharks than trawling alone (Vooren and Klippel 2005). A low rate of dispersal between angel shark populations makes them especially prone to local depletion and means that recolonisation will be extremely low.
Fishery landing statistics of "angel shark" in southern Brazil refer to S. guggenheim, S. occulta and S. argentina combined. The term "angel shark" in the present assessment refers to this assemblage of species. These three species occur on the continental shelf with S. argentina and S. occulta also occurring on the upper slope. Annual catches of angel shark from the continental shelf peaked at about 2,000 t in 1986 to 1989 and again in 1993, and then decreased to 900 t in 2003. Angel shark CPUE by otter trawl and pair trawl on the continental shelf decreased by about 85% from 1984 to 2002 (Miranda and Vooren 2003, CEPERG 2003, GEP/CTTMar 2003). In the trawl and gillnet fishery for monkfish Lophius gastrophysus at the shelf edge and upper slope, S. occulta and S. argentina have been significant bycatch species, indicating that there is also considerable pressure on the outer shelf and slope for S. argentina. Additionally, an angel shark bottom gillnet fishery on the outer shelf commenced around 1990 and at present large amounts of angel shark are caught this way (Miranda and Vooren 2003). Research trawl surveys of the outer shelf in the years 1986/87 and 2001/02 confirmed that in southern Brazil the abundance of S. argentina has decreased to 15% of its original level and this is attributed to recruitment overfishing primarily due to the bottom gillnet fishery (Vooren and Lamónaca 2002, Vooren and Klippel 2005). Perez and Warhlich (2005) noted that Squatina argentina was one of the most retained bycatch species in the gillnet monkfish fishery, with bycatch estimated at 1.052 per 100 nets in 2001 (total 8,698 individuals), and these authors suggest that this is unlikely to be sustainable for the species.
At present there is no evidence of the existence of abundant populations of the species outside southern Brazil. In Uruguay and Argentina the species is uncommon in commercial landings but its distribution and abundance have not been studied. In Argentina, angel shark landings have shown a negative trend since a peak in 1998 (Massa et al. 2004), but landings apparently consist almost entirely of S. guggenheim. In Uruguay there is little direct fishing for angel sharks, but they are taken as bycatch in industrial and artisanal fisheries. The estimated capture has been 300 to 400 MT per year since 1997. There are no statistics by species, but the largest captures probably correspond to S. guggenheim and S. argentina (A. Domingo pers. comm). While most information is available from Brazil, trawl and other demersal fisheries operate over the species' area of occurrence, exerting fishing pressure across both the latitudinal and bathymetrical range of the species.
Since 1992 there is a Maximum Permitted Catch (MPC) for angel sharks in Argentina which was 6,000 MT in the years 1995 to 1999 and thereafter was reduced to 4,000 MT (Massa et al. 2003).
In Brazil there is no control of the shelf angel shark fishery, and although trawling in inshore waters is prohibited, enforcement of this regulation is difficult. A management plan was developed for the gillnet monkfish fishery in 2002 and approved in June 2005. Foreign chartered fishing vessels were unauthorized to operate after October 2002 and an annual TAC of 1,500 t and an effort limitation of nine vessels implemented for the domestic fleet. Further management arrangements included a permanent VMS tracking system, 100% observer coverage, logbooks and a ban on fishing shallower than 250 m. Furthermore, two no-take zones were implemented, one in the southern and the other in the northern sections of the fishing area (Perez et al. 2002, Perez pers. comm). The conservation status of this species will rely heavily upon the success of these management arrangements. Full observer coverage onboard domestic vessels should provide accurate monitoring of trends in the future.
|Citation:||Vooren, C.M. & Chiaramonte, G.E. 2006. Squatina argentina. The IUCN Red List of Threatened Species 2006: e.T39329A10202418.Downloaded on 25 November 2017.|