|Scientific Name:||Squatina guggenheim Marini, 1936|
|Infra-specific Taxa Assessed:|
|Taxonomic Source(s):||Stelbrink, B., von Rintelen, T., Cliff, G. and Kriwet, J. 2010. Molecular systematics and global phylogeography of angel sharks (genus Squatina). Molecular Phylogenetics and Evolution 54: 395-404.|
|Taxonomic Notes:||There is some controversy concerning the taxonomy and 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 and 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. a) 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. In this assessment, S. guggenheim Marini, 1936 is presented, which Vooren and Silva (1991) consider S. punctata to be a junior synonym of, but which Soto (2001) and Compagno (in prep. a) refer to as S. punctata Marini, 1936.
|Red List Category & Criteria:||Endangered A2bd ver 3.1|
|Assessor(s):||Chiaramonte, G. & Vooren, C.M.|
|Reviewer(s):||Musick, J., Kyne, P. & Valenti, S.V. (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.
Squatina guggenheim was assessed as VU A1bd+2d globally and EN A1bd+2d for Brazil on the 2000 Red List. It is updated here due to better information and further evidence of declines.
Squatina guggenheim is endemic to the Southwest Atlantic from Rio de Janeiro, Brazil (24°S) through Uruguay to northern Patagonia, Argentina (43°S) on the shelf at 10 to 150 m depth. The species' low reproductive potential (litter size of 3 to 9 and triennial female breeding cycle) together with its vulnerability to both trawl and gillnet gear makes it highly susceptible to population depletion. Angel sharks are heavily fished in southern Brazil and significant declines have been documented there. An angel shark bottom gillnet fishery commenced around 1990 and at present large amounts of angel shark is 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. guggenheim had decreased by 85%, which was attributed to recruitment overfishing. Furthermore, pupping and nursery areas in Brazil occur in shallow inshore waters at depths of <30 m. Intensive fishing by gillnet and trawl in these nursery areas results in additional pressure on gravid females and juveniles of the species (Silva 1996, Vooren and Klippel 2005). In Argentina, landings consist apparently almost entirely of S. guggenheim with a negative trend in landings evident since 1998 after the catch peaked. Given that intensive fisheries occur throughout the species' range, together with its vulnerability to depletion, high exploitation of areas of critical habitat and the evidence that off Brazil, fishing has reduced previously abundant stocks to 15% of the original levels, S. guggenheim is assessed as Endangered. Overall, fishing continues without restraint throughout the Brazilian range of S. guggenheim and the protection of critical nursery areas as well as fisheries controls is urgently required for its conservation. In the first instance, the resolution of taxonomic and nomenclatural issues, in order to accurately define the occurrence, distribution and declines of individual species, is paramount to the conservation of Southwest Atlantic angel sharks.
|Previously published Red List assessments:|
|Range Description:||Squatina guggenheim is endemic to the Southwest Atlantic occurring from 24°S (Rio de Janeiro, southern Brazil) through Uruguay to 43°S (northern Patagonia, Argentina). Gosztonyi (1981) recorded specimens of Squatina spp. from 47°S, which may be this species, however this requires confirmation. Gravid females migrate in spring to shallow inshore nursery grounds to give birth (Silva 1996).|
Native:Argentina; Brazil; Uruguay
|FAO Marine Fishing Areas:|
Atlantic – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Although the species lives in a geographical continuum of ~20 degrees of latitude, the range is probably composed of local populations each with its own inshore-offshore migration pattern within their local temperature regime. One such population exists in southern Brazil. These local populations can be extirpated by fishing activities. Shallow inshore regions are important as nursery grounds throughout the geographical range of the species.|
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Squatina guggenheim is a relatively small, shelf bottom-dwelling shark. In Brazil the species occurs mostly at depths of 10 to 80 m at bottom temperatures of 10 to 22°C (Vooren and Silva 1991). Cousseau (1973) refers to captures of S. guggenheim from the coast to 150 m in Argentinean waters, Gosztonyi (1981) at depths of 26 to 135 m, and Menni et al. (1981) at 22 to 121 m. |
Maximum size in Brazil is 92 cm TL (Silva 1996); size at maturity 70 to 80 cm TL for both sexes (Cousseau 1973, Vooren and Silva 1991). Aplacental yolksac viviparous with one functional ovary. Number of embryos per litter is 3 to 9 (Vooren and Klippel 2005, Compagno in prep). The breeding cycle of the female is triennial (Vooren and Klippel 2005). Squatina guggenheim migrates in spring to shallow coastal waters where the females give birth and where small juveniles occur all year round (Vooren and Silva 1991, Vooren and Klippel 2005). For S. guggenheim in southern Brazil, Vieira (1996) established the following Von Bertalanffy parameters: K=0.274, L∞=94.7 cm TL, and t0=-1.145. The age at sexual maturity was calculated as 4 to 5 years and longevity 12 years. For Argentina, Chiaramonte (unpublished data) calculated K= 0.107 using the indirect methods of Holden (1974).
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).
Gravid females of S. guggenheim have been observed to abort embryos easily upon capture, further reducing the reproductive capacity (Vooren and Klippel 2005). A low rate of dispersal between populations also makes them especially prone to local depletion and means that recolonisation will be extremely low. Furthermore, pupping and nursery areas in Brazil occur in shallow inshore waters at depths of
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 also occurring on the upper slope. Annual catches of angel shark from the continental shelf peaked at about 2,000t in 1986-1989 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, Vooren and Klippel 2005). While S. occulta and S. argentina have been significant bycatch species in the trawl and gillnet fishery for monkfish Lophius gastrophysus at the shelf edge and uppermost slope, S. guggenheim occurs shallower than that fishery.
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. guggenheim 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).
In Argentina, the shark bycatch from gillnet and bottom trawl fleets targeting species such as school shark, croakers and flatfishes is poorly known. However, Cousseau (1973), based on Nani and Gonzalez Alberdi (1966), estimated Squatina as 6% of the total weight of the catches of the coastal bottom trawling fleet. The predominant size in these catches was about 70 to 80 cm TL; small sizes (25 to 45 cm TL) were uncommon. Cousseau (1973), based on García Cabrejos and Malaret (1969) calculated the total landings of angel shark in Mar del Plata harbour in 1964 to be 1,074 MT and 2,355 MT in 1965. Otero et al. (1982) considered the angel sharks to be species with a low concentration on the Buenos Aires coast, with an annual biomass for 1981/2 estimated at 4,050 tons. However, in 1991 as much as 4,167 MT were taken, and 4,281 MT in 1996. Chiaramonte (1998) stated that the angel sharks were the second most important fish landed by the gillnet fleet of Puerto Quequen. Total captures of angel sharks in Argentina oscillated around 1,000 MT between 1979 and 1984 then increased to maximums of over 4,000 MT in the 1990s. Catches consist almost entirely of S. guggenheim. Peaks were reached in 1997 and 1998, before landings dropped in 2002 to 2,000 MT, rising again in 2003 to 3,550 MT (Massa et al. 2004). Thus there has been an overall negative trend in landings during the period 1998-2003 (Massa et al. 2004). Furthermore, Vooren and Klippel (2005) (citing Massa and Hozbor 2003) suggested a 58% decline in the CPUE of angel shark in the coastal bottom trawl fleet.
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 largest captures probably correspond to S. guggenheim and S. argentina (A. Domingo pers. comm).
Since 1992 there has been a Maximum Permitted Catch (MPC) for angel shark 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.
Vooren and Klippel (2005) recommend the protection of the coastal nursery grounds in southern Brazil (waters south of 32°30'S) from fishing as an essential measure for the conservation of this species.
|Citation:||Chiaramonte, G. & Vooren, C.M. 2007. Squatina guggenheim. The IUCN Red List of Threatened Species 2007: e.T39330A10202558.Downloaded on 12 December 2017.|
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