|Scientific Name:||Rhizoprionodon terraenovae|
Squalus terraenovae Richardson, 1836
|Red List Category & Criteria:||Least Concern ver 3.1|
|Reviewer/s:||Musick, J.A. & Fowler, S.L. (Shark Red List Authority)|
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).
The Atlantic Sharpnose Shark (Rhizoprionodon terraenovae) is a very abundant, small coastal shark found in warm temperate and tropical waters of the western North Atlantic. It is caught in both commercial and recreational fisheries, and in incidental fisheries, mainly as bycatch in gillnets and shrimp trawl fisheries. A fast maturing, relatively fecund species with moderate population growth rates and short generation times. The juvenile and adult stages seem to affect population growth rates almost equally. The species is assessed as Least Concern because of its abundance and life history characteristics, which make it less susceptible to removals than many other species of sharks.
|Range Description:||The Atlantic Sharpnose Shark occurs in the western North Atlantic, ranging as far north as New Brunswick, Canada, to the Yucatan Peninsula in the south, including the Gulf of Mexico.|
Native:Canada; Mexico; United States (Alabama, Connecticut, Delaware, Florida, Georgia, Louisiana, Maine, Maryland, Massachusetts, Mississippi, New Hampshire, New Jersey, North Carolina, Rhode Island, South Carolina, Texas, Virginia)
|FAO Marine Fishing Areas:||
Atlantic – northwest; Atlantic – western central
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The Atlantic Sharpnose Shark is an abundant, small coastal shark of warm temperate and tropical waters (Compagno 1984b).|
|Habitat and Ecology:||
This species is commonly found off sandy beaches and in estuaries and enclosed bays and sounds, mostly over mud and sand bottoms. There is a seasonal inshore-offshore migration, with individuals moving to deeper offshore waters in winter (Compagno 1984).
The Atlantic Sharpnose Shark is a small, coastal carcharhinid that rarely exceeds 110 cm total length (TL). The life history of this species in the US Gulf of Mexico has been fairly well described. In this area, female seldom exceeds 107 cm TL and males rarely surpass 105 cm TL. Females generally mature between 85?90 cm TL (or 2.8?3.9 years of age) and males mature between 80?85 cm TL (or 2.4?3.5 years of age) (Parsons 1985, Branstetter 1987). Thus, both males and females reach maturity at about 80% of their maximum size. Maximum observed ages in two separate studies were 6+ years and 7+ years for both sexes combined, whereas theoretical longevities derived from von Bertalanffy growth curves predict that this species should reach at least 10 years (Cortés 2000a). Recent tag-recapture information has shown that this species can live to at least nine years (J. Carlson pers. comm.).
The Atlantic Sharpnose Shark is a placental viviparous species that reproduces annually. Gestation period has been reported to last from 10?12 months; litter size is generally 4?6, ranging from 1?7. Offspring are born at 30?35 cm TL or about 30% of maximum adult size. There is a positive correlation between maternal size and litter size and evidence of a trade-off between the number and size of offspring, i.e. there is a negative correlation between litter size and offspring size (Parsons 1983). Mating occurs between mid-May and mid-July and parturition generally takes place mostly in June. The sex ratio at birth is 1:1.
This species uses enclosed bays and sounds as nursery areas. Despite the abundance of this shark, its diet has not been very well described quantitatively. It is dominated by teleost fishes (66%) and crustaceans (32%), but also includes some molluscs (Branstetter 1981, Gelsleichter et al. 1999, Cortés unpubl. data).
Cortés (1995) extensively studied the demography of the Atlantic Sharpnose Shark in the Gulf of Mexico and found that the life history characteristics of this species did not allow it to withstand the levels of fishing mortality it was thought to be subjected to. Recent demographic studies of this species by Cortés (in press) that incorporate uncertainty in estimates of vital rates indicate that the Atlantic Sharpnose Shark has moderate population growth rates (?) (mean=1.056 yr-1; 95% confidence interval = 0.970?1.195 yr-1) and short generation times (?) (mean=4.9 years, 95% CI = 4.0?5.4 years). Elasticity analysis (which examines the proportional sensitivity of ? to a proportional change in a vital rate) also showed that ? is more sensitive to juvenile survival and adult survival than to fertility (which includes survival to age-1). Annual survivorship values used in Cortés (2002) were estimated through five indirect life history methods and ranged from 55?79%.
In the United States, Atlantic Sharpnose Sharks are caught in commercial and recreational fisheries and also as bycatch. Recent commercial landings of this species indicate that it accounted for over one-third of all landings of small coastal sharks in the south-eastern United States during 1996?1999. In 1998 and 1999, over 90% of small coastal sharks were landed in Florida?s east coast, the majority of which were caught with drift gillnet gear. Commercial landings of Atlantic Sharpnose Sharks averaged 61,000 individuals from 1995?1999 (Cortés 2000b).
Recreational catch estimates from several surveys indicate that about 72,000 Atlantic Sharpnose Sharks were caught annually from 1981?1998, ranging from a minimum of about 18,000 sharks in 1985 to a peak of about 137,000 sharks caught in 1991 (Cortés 2000b). Additionally, bycatch estimates from the shrimp trawl fishery operating in the Gulf of Mexico indicate that about 1.75 million individuals were caught annually from 1972?1999 (Cortés unpubl.).
The Atlantic Sharpnose Shark is also heavily exploited in Mexico. A monitoring programme conducted in the Gulf of Mexico between November 1993 and December 1994 showed that it is the most important species in the artisanal fisheries, accounting for 46% of the landings numerically, especially in Campeche where 46% of the total is landed (Castillo et al. 1998). By month, the highest landings corresponded to May and October. This species is caught mostly with gillnets. Elsewhere this species has been documented as bycatch in Canada.
Nursery areas for this species are located inshore and adults frequent inshore waters, making this species vulnerable to exploitation and human-induced habitat degradation.
In the United States, the Atlantic Sharpnose Shark is classified as a small coastal species in the Federal Management Plan (FMP) for Sharks of the Atlantic Ocean, Gulf of Mexico and Caribbean, together with the Blacknose Shark (Carcarhinus acronotus), the Finetooth Shark (C. isodon), the Bonnethead Sharl (Sphyrna tiburo), the Smalltail Shark (C. porosus), the Atlantic Angel Shark (Squatina dumeril) and the Caribbean Sharpnose Shark (Rhizoprionodon porosus) (NMFS 1993). The small coastal shark complex is not currently considered to be overfished, but there are fishing regulations in effect, which include an annual commercial quota of 1,760 t dressed weight, and a recreational daily bag limit of two sharks per vessel per trip, with an additional allowance of two Atlantic Sharpnose Sharks per person per trip. A more recent FMP (NMFS 1999) called for more stringent measures, including a reduction of the annual commercial quota for small coastal sharks to 359 t and making the Atlantic angelshark, Caribbean sharpnose and smalltail sharks prohibited species.
This is a very abundant species, with early age at maturity, short lifespan and generation time, and moderately high litter size and population growth rates, capable of withstanding a higher level of removals than many other species of sharks. It is thus considered to be of low risk of extinction because of its life history and population characteristics.
|Citation:||Cortés, E. 2009. Rhizoprionodon terraenovae. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 23 May 2013.|
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