|Scientific Name:||Squatina formosa|
|Species Authority:||Shen & Ting, 1972|
|Red List Category & Criteria:||Endangered A2d+4d ver 3.1|
|Assessor(s):||Walsh, J.H. & Ebert, D.A.|
|Reviewer(s):||Valenti, S.V., Gibson, C.G. & Fowler, S.L. (Shark Red List Authority)|
The Taiwan Angelshark (Squatina formosa) is a medium-sized angel shark found in the northwest Pacific on the continental shelf surrounding Taiwan, Province of China. Usually it occurs at depths of 100-300 m, although it is likely also to occur in shallower depths. It is caught as bycatch, particularly in large numbers in demersal trawl fisheries. The species is not known to be targeted, but is a retained bycatch, with individuals recorded in local fish markets in northern Taiwan, although this species, like other northwest Pacific angel sharks, frequently has been misidentified. Taiwan's main fisheries (including longline, trawl and gillnet gear), operate throughout this species' entire limited known range. The Taiwan Angelshark's generation period may be between 8 and 15 years, based on biological information from better known angel sharks. Other angel shark populations (for example Squatina squatina and Squatina guggenheim) have proved particularly vulnerable to trawl and gillnet fishing gear, resulting in significant population depletion because of their low reproductive potential and low potential for re-colonisation. Where population data are available for other angel sharks, declines greater than 80% have been observed in less than three generations within areas where target or bycatch fisheries take place. Although trend data are not available for the Taiwan Angelshark, there is concern that it has already declined significantly as a result of fisheries, which operate throughout its entire known range. Based on current knowledge of fisheries in this region, these trends are likely to continue. Given that it is fished throughout its range with no refuges from fishing pressure, it is assessed as Endangered A2d+A4d, based on continuing suspected declines of 50-80%.Further research into this species' abundance, distribution, life-history and population trends is urgently needed.
|Range Description:||Northwest Pacific: East China Sea (Compagno et al. 2005a, Walsh and Ebert 2007), continental waters surrounding northern Taiwan, Province of China, and East Taiwan Strait (Shuyuan 1994).
Specimens from the Philippines previously identified as this species were misidentified. These specimens are likely an undescribed species (J.H. Walsh and D.A. Ebert pers. obs. 2007).
Native:Taiwan, Province of China (Taiwan, Province of China (main island))
|FAO Marine Fishing Areas:||
Pacific – northwest
|Range Map:||Click here to open the map viewer and explore range.|
No details are available on the population of this species. Individuals are found in local fish markets in Taiwan. Little data exist due to a total lack of known catch records for this species and problems distinguishing individuals of this species from other northwest Pacific angel sharks.
Where population data are available for other angel sharks, declines greater than 80% have been observed in less than three generations, within areas where target or bycatch fisheries take place. For example, Squatina squatina has been extirpated from several parts of its range in the northeast Atlantic and Mediterranean, where it is taken as bycatch, as a result of continued intense fishing pressure (Morey et al. 2006, ICES 2004).
|Habitat and Ecology:||
A little known species, caught at or near the bottom on the continental shelf, usually at depths of 100-300 m, although it is likely to occur in shallower depths also (D.A. Ebert unpublished data). Other angel sharks are known to bury themselves in sediment and ambush their prey.
Though life history parameters are unknown, this species is thought to be slow growing and late maturing like other species of angel shark. Reproduction is aplacental viviparity (D.A. Ebert unpublished data). Size at maturity is unknown, but large, in excess of 100 cm total length (TL) (D.A. Ebert unpublished data). Maximum recorded size is 150 cm TL and size at birth is ~30-40 cm TL (D.A. Ebert unpub. data).
Taiwan's main fisheries operate throughout the entire known range of this species (D.A. Ebert pers obs. 2007). It is caught in bottom trawl fisheries, which operate between 50 and 300 m (D. Ebert pers. obs. 2007). This species is utilized and is found in local fish markets, but it is unknown whether this species is truly targeted by fishing operations.
The East China Sea is intensively exploited, with several stocks declining due to overfishing and pollution (NOAA 2004). Heavy fishing mortality has resulted in a shift from an older, traditional fishery based on high-value demersal species to faster-growing, smaller, and lower-value species such as shrimp and cephalopods (NOAA 2004). Fishing pressure from trawl vessels is intense off China, despite bans on bottom trawling in various areas. China has the largest number of fishing vessels and fishers in the world with a marine fishing fleet consisting of 279,937 motorized vessels in 2004 (1,996 of which were confined to distant waters), showing little change from 1999 (FAO 2007). Catches have declined as a result, leading to catches of immature, small-sized and low value organisms (FAO 2007). In 2004, the most common fishing gear used was the trawl net (in terms of production, trawlers accounted for 47.6% of catches in 2004 (FAO 2007). In February 2006, the Government of China issued the Programme of Action on Conservation of Living Aquatic Resources of China. This states that by 2010 they aim to reduce the size and power of the motorized marine fishing fleet and the corresponding domestic marine capture catch in China from 220,000 vessels with a total power of 12.7 million kW and catching 13.06 million tonnes marine organisms in 2002, to 192,000 vessels, 11.43 million kW (FAO 2007). This represents a decline in fishing power of only 10%.
Other angel shark populations (e.g. Squatina californica, S. squatina, S. argentina) have proved particularly vulnerable to fishing pressure due to their low reproductive potential, vulnerability to trawl and gillnet fishing gear and low potential for recolonisation (due to their sedentary habit) (Gaida 1997, ICES 2004, Morey et al. 2006, Vooren and Klippel 2005). Squatina guggenheim and Squatina occulta, which occur in the Southwest Atlantic Ocean, have a triennial reproductive cycle, with a litter size of only two to eight pups. This extended breeding cycle means that they have a very low intrinsic rate of population growth. Consequently, these sharks are generally highly vulnerable to extirpation through bycatch in fisheries that are managed to sustain production of other, more productive, fishes (Musick et al. 2000, C. Vooren pers. comm. 2007).
No known specific conservation actions exist.
According to the Law of Fisheries of China, bottom trawling is banned within certain areas of Chinese waters (Y. Wang pers. comm. 2007). Bottom trawling is restricted in certain zones and at different times in shallow water. Individual Provinces are responsible for applying national regulations within China. They also can apply their own regulations, on basis of national regulations, but no specific information is available on the areas or timings involved or the effectiveness of enforcement.
Catch levels need to be accurately quantified and monitored. Resolution of the taxonomic issues and identification problems associated with this genus in the northwest and western central Pacific should be a high priority to achieve this (Walsh and Ebert 2007). Management action will most likely be required to reduce bycatch of this species.
|Citation:||Walsh, J.H. & Ebert, D.A. 2009. Squatina formosa. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 28 July 2015.|
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