|Scientific Name:||Cephaloscyllium ventriosum|
|Species Authority:||(Garman, 1880)|
Cephaloscyllium uter (Jordan & Gilbert, in Jordan & Evermann, 1896)
Scyllium ventriosum Garman, 1880
|Taxonomic Source(s):||Eschmeyer, W.N. and Fricke, R. (eds). 2015. Catalog of Fishes: genera, species, references. Updated 1 October 2015. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 1 October 2015).|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Villavicencio-Garayzar, C.J., White, C.F. & Lowe, C.G|
|Reviewer(s):||Jew, M.L. & Nehmens, M.C.|
|Facilitator/Compiler(s):||Lawson, J., Walls, R.H.L., Ebert, D.A. & Dulvy, N.K.|
Swell Shark (Cephaloscyllium ventriosum) is a nocturnal benthic and epibenthic catshark with a disjunct distribution in the Eastern Pacific, from California to southern Mexico, and off central Chile. It has been recorded inshore to 457 m depth, but is most commonly found at 5 to 40 m. The species is oviparous, but annual egg production is unknown. In California, this species has not been present in recent commercial landings data, though it is likely occasionally caught by recreational anglers and divers. It is also targeted for the aquarium trade. In Mexico, Swell Shark is caught as minor bycatch in gillnets and trawls. Gillnet landings data and fisheries-dependent surveys in Baja California suggest that this species is uncommon bycatch, comprising only 1% of reported landings and 1% of total elasmobranch catches in the fisheries-dependent survey. Moreover, Swell Shark was represented only 0.6% of discarded carcasses in Baja California artisanal fishing camps. Given that there is no value for their meat or fins in Baja California, such low discards suggest that this species may be indeed uncommon in gillnet bycatch. As landings are either absent or minor for this species throughout its range, and no demand for meat or fins is reported or anticipated in the near future, this species is assessed as Least Concern throughout its range. Gathering information on both the potential impact of the marine aquarium trade and the little-known Chilean population should be a top priority as no information currently exists.
|Previously published Red List assessments:|
Swell Shark is an Eastern Pacific species with a disjunct range. It has been found from California, USA to southern Mexico including the Gulf of California and off central Chile (Schaaf-Da Silva and Ebert 2008). The absence of records from between these regions, that is the tropical Eastern Pacific, suggests that either this species is not suited to tropical waters or that there has been a lack of surveys in the area (Ebert 2003).
Native:Chile; Mexico (Baja California, Baja California Sur, Colima, Guerrero, Jalisco, Michoacán, Nayarit, Oaxaca, Sinaloa, Sonora); United States (California)
|FAO Marine Fishing Areas:|
Pacific – eastern central; Pacific – southeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Despite the patchiness of Swell Shark records, morphometric data suggest that a single global population exists from California to Chile (Schaaf-Da Silva and Ebert 2008). This species is considered very common in the Californian waters south of Point Conception (Ebert 2003) and in the northern Gulf of California (Castro 2011). The Swell Shark population in the waters surrounding Catalina Island, California decreased over a 20-year period, which has been attributed to an increase in the surface water temperatures due to El Nino events (Strong 1989, Ebert 2003). A survey using horizontal gill nets was conducted in the waters surrounding Santa Catalina Island and southern California's mainland from August 1996 to June 1998 (Pondella et al. 2000). Among the 98 species from 47 families encountered off Santa Catalina Island, Swell Shark was the fifteenth most abundant fish in terms of biomass. Among the 95 species from 45 families encountered off mainland California, Swell Shark was the second most abundant species in terms of biomass. In another study, underwater surveys conducted on several islands in southern and Baja California encountered subadults off San Nicholas island, but no other individuals were encountered on any of the other seven study sites (Pondella et al. 2005).|
A fisheries-dependent survey of Baja California artisanal gillnet and longline vessels was conducted from September 2006 to December 2008, where elasmobranchs found in catches were identified to species level and catch per unit effort (CPUE) was calculated (Cartamil et al. 2011). For Swell Shark, a CPUE of 0.32 individuals per fishing trip was calculated for artisanal gillnets, which made up 1% of the total catch over the survey period. By comparison, Shovelnose Guitarfish (Rhinobatos productus) had a reported CPUE of 14.93 individuals per fishing trip and made up nearly half of the total catch over the survey period. Carcass discard sites, located outside of fishing camps, were also surveyed and found that Swell Shark comprised only 0.59% of individuals documented, with Blue Shark (Prionace glauca) making the majority (33.29%) of discarded carcasses. As Swell Shark had no value to fishers for either their meat or fins, and thus presumably would be discarded, this suggests that catches may be relatively low.
|Current Population Trend:||Unknown|
|Habitat and Ecology:||Swell Shark can be found in benthic and epibenthic habitats on the continental shelf and upper slope to 500 m, but is most common at 5 to 40 m (Roedel and Ripley 1950, Feder et al. 1974, Compagno 1984, Ebert 2003, Schaaf-da Silva and Ebert 2008). It prefers rocky, algal-covered areas of kelp beds (Castro 2011), but also inhabits algal-covered bottoms without kelp. This species is primarily nocturnal, resting in caves and crevices during the day, often in aggregations.|
This species is oviparous, with eggs hatching after 7.5 to 10 months (Castro 1983), or up to 12 months (Castro 2011) depending on water temperature. Egg cases are measure 9-12.5 cm long and 2.8-5.5 cm wide (Cox 1963). Size at hatching is 13-15 cm total length (TL). Eggs are deposited by females and attach to benthic vegetation by anterior tendrils that can range from 130-150 cm and posterior tendrils of 60-70 cm (Eschmeyer and Herald 1983). Females have only one egg-case per oviduct at a time (Ebert 2003). Egg-laying rates and seasonality, and therefore annual egg production, is not known. Adult males were found to mature at 82-85 cm TL (Compagno et al. 2005), and the maximum size recorded of either sex has been 110 cm TL (Castro 1983).
|Use and Trade:||Swell Shark is a popular aquarium species as it reproduces easily under captive conditions, and offspring survive well in captivity. The extent of the aquarium trade fishery is not known at present. It is also possibly used for fishmeal when taken as bycatch (Compagno in prep.)|
Swell Shark is not targeted commercially (Moreno-Báez et al. 2012). While this species is taken as a minor bycatch in gillnets and trawls, its habitat (rocky reefs and kelp) is generally unsuitable for trawling, providing the species protection from fishing. Swell Shark is captured in both the small scale lobster trap fishery and the set gill net fishery as a small percentage of the bycatch in Baja California, Mexico (Shester and Micheli 2011). Approximately 1% of gill net landings along the pacific coast of Baja California are comprised of this species, and it is absent from long line catches (Ramirez-Amaro et al. 2013). Ramirez-Amaro et al. (2013) also noted that this species was usually caught as juveniles, suggesting that fishing effort might be opportunistically targeting nursery areas. A survey of the artisanal gillnet fishery in Baja California found that this species comprised only 1% of total elasmobranch catches, and was not valued either for its flesh or fins. This study also found carcasses of this species at discard sites surrounding fishing camps, representing only 0.6% of all carcasses (Cartamil et al. 2011). Along the Sonoran coast of the Gulf of California in Mexico, (Bizzarro et al. 2009) observed that this species is landed by artisanal fishers, however, it represented less that 1% of the total catch. There was no size difference among landed males and females, however, there was 2-fold more males landed than females.
This species is listed by the United States National Marine Fisheries Service as a landed species, however, there are no listings for this species in any recent years (PacFin). For the years in which this species was recorded, there were minimal landings, with only 1978 having the west coast shark fishery land more than 1,000 pounds (Holts, 1988).
However fisheries data often lists shark as “other”, which could possibly obfuscate true landings. This is especially true in Mexico, where small sharks are simply listed as cazonés. However, species-specific surveys in Baja California do suggest that this species may indeed be relatively uncommon in catches. This species is occasionally taken by recreational anglers and spearfishers (Compagno in prep), but this catch is likely not significant.
General life history information and catch data (the latter particularly for the Chile subpopulation) are required. The extent to which Swell Shark enters the marine aquaria trade needs to be determined.
In México, a moratorium on the issue of elasmobranch fishing permits was enacted in 1993, but no formal management plan has been implemented. Since then, Mexican regulations limit gillnet fisherman to one gillnet per vessel with a minimum mesh size of 15 cm. However, few fishermen understood the new regulatory guidelines and even fewer complied (Cartamil et al. 2011, NOM-029-PESCA-2006).
Elasmobranch fisheries are largely unmanaged throughout Central and South America, and elasmobranch landings reported from Mexico and Central America typically lack species-specific details. Large sharks are generally grouped as tiburones and small sharks as cazonés, while batoids are often simply termed manta raya collectively. Mexican federal fisheries agencies recently began providing slightly more taxonomic resolution of ray landings by listing several new categories.
|Citation:||Villavicencio-Garayzar, C.J., White, C.F. & Lowe, C.G. 2015. Cephaloscyllium ventriosum. The IUCN Red List of Threatened Species 2015: e.T60227A80671800.Downloaded on 30 June 2016.|
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