|Scientific Name:||Squatina nebulosa Regan, 1906|
|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:||Diagnostic features include pelvic fin tips which do reach the first dorsal origin, angular pelvic, dorsal and caudal fins, and a upper lip arch which is semi-oval in shape. This species does not possess distinct ocelli or midback spines. This poorly known species is often misidentified as S. formosa, but in a recent revision of this genus Walsh and Ebert (2007) resolved some of the characteristics between these two species. Some of the confusion resulted from the original description of S. formosa which was partially based on three designated paratypes that were all in fact S. nebulosa.|
|Red List Category & Criteria:||Vulnerable 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 Clouded Angelshark (Squatina nebulosa) is a large angel shark found in the northwest Pacific, in the Sea of Japan, the Yellow Sea and the East China Sea. It is found on the continental shelf and upper slope. It is caught as bycatch in fisheries, which operate down to 600 m, and in particularly large numbers in demersal trawl fisheries. It is not known to be targeted, but is a retained bycatch, with individuals found in local fish markets in northern Taiwan, Province of China and Japan, although this species, like other northwest Pacific angel sharks, has frequently been misidentified. This species' generation period may be ~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 Clouded Angelshark, there is concern that it has already declined significantly as a result of fisheries, which possibly operate throughout its range. Based on current knowledge of fishing pressure in this region, these trends are likely to continue. This species, however, has a fairly wide geographic and bathymetric range, which may offer some areas of refuge from fisheries. It is therefore assessed as Vulnerable A2d+A4d, based on suspected declines approaching 50%, but it may prove to have been more seriously depleted than this. Further research into this species' abundance, distribution, life-history and population trends is urgently needed.
|Range Description:||Endemic to western north Pacific including southern Japanese waters, central and eastern north China Sea, western Taiwan Straits (Shuyuan 1994), and waters surrounding northern Taiwan (Compagno et al. 2005a, Walsh and Ebert 2007).|
Native:China; Japan (Hokkaido, Honshu, Kyushu, Shikoku); Korea, Democratic People's Republic of; Korea, Republic of; 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.|
|Population:||Population size for this species is unknown, but individuals are found in local fish markets in Taiwan and Japan (H. Ishihara and D. Ebert pers. obs. 2007). Little data exist due to no known catch records for this species and confusing taxonomic information used to distinguish individuals of this species from other northwest and western central Pacific Squatinids, especially Squatina formosa.|
In 1980, one specimen of this species was caught in each of seven surveys that were carried out in the East China Sea between 35 and 500 m (Yamada et al. 2007).
|Current Population Trend:||Unknown|
|Habitat and Ecology:||Found on the continental shelf and caught in fisheries operating down to 600 m (D.A. Ebert pers. obs. 2007). Maximum total length is 200 cm (Yamada et al. 2007). Though life history parameters are unknown, this species is thought to be slow growing and late maturing like other Squatinids.|
Individuals are caught at or near the bottom, often in sandy substrate (Compagno 1984). Other species of angel shark are known to bury themselves in sediment and ambush their prey. Reproduction strategy is aplacental viviparity (D.A. Ebert pers. obs. 2007).
This species is taken as a retained bycatch in trawl fisheries which operate over large areas of its range. It is found in local fish markets, but it is unknown whether this species is truly targeted by fishing operations (D. Ebert pers.obs. 2007). This species' bathymetric distribution extends deeper than other northwest Pacific Squatina species', and may afford it some refuge from fishing in areas not exploited by deepwater fisheries.
The East China Sea and Yellow Seas are intensively exploited, with several stocks declining due to overfishing and pollution (NOAA 2004ab). 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 2004a). The Yellow Sea was once one of the most intensively exploited Large Marine Ecosystems (LME) in the world and is considered severely impacted in terms of overfishing, with destructive fishing practices (NOAA 2004b).
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 2007b). Catches have declined as a result, leading to catches of immature, small-sized and low value organisms (FAO 2007b). 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 2007b). Progress is being made in the introduction of ecosystem based management in the Yellow Sea and a fisheries recovery plan requires the cooperative effort of all countries bordering it. The Yellow Sea LME Project will assess fish stocks and establish TACs (NOAA 2004b). 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 2007b). 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 nebulosa. The IUCN Red List of Threatened Species 2009: e.T161325A5398349.Downloaded on 17 December 2017.|