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Sharks: Species at Risk

Basking sharks are the second largest living shark, easily distinguished by their huge mouths. These slow, harmless sharks often swim with their mouths open wide in order to filter-feed on plankton, copepods, larvae and fish eggs.

Easily identified from other grey sharks by a black or dusky spot beneath the snout tip, the blacknose shark has an unusually fast growth rate. Blacknose sharks reach maturity in just two years and produce three to six young at a time.

Blue sharks are one of the most wide-ranging and previously abundant shark species. Now, they are the most heavily fished shark in the world. An estimated 10-20 million individuals are killed by pelagic fisheries annually, mostly as bycatch.

The Caribbean reef shark is found from the coast of North Carolina to the coast of Brazil. As the name suggests, this species is found most often around coral reefs and is considered the most abundant reef shark in its region.

Since sharks lack a swim bladder, they use oil in their livers to regulate their buoyancy. Deep-sea sharks, those living below 300 meters, have huge livers with more oil to adjust to these depths. As a result, they are caught by deep-sea trawls, gillnetts and longlines for an oily substance found in their livers called squalene. Squalene, or its derivative squalane, is found in many cosmetic products.

Among one of the slowest growing sharks in the world, the dusky shark takes 20 years to reach maturity and has a 16 month gestation period. This low rate of increase makes dusky sharks particularly vulnerable to exploitation.

Globally, the dusky shark is classified as vulnerable by the IUCN. The Gulf of Mexico population suffered a 79 percent decline between the 1950s and the 1990s. Their main threats include overfishing and bycatch on commercial longlines in the swordfish and tuna fishery.

As the biggest meat-eating sharks, great white sharks average between 4 and 7 meters but have been recorded at lengths over 11 meters. Great white sharks, which have torpedo-shaped bodies and pointed snouts, get their name from the distinctive white coloring on their undersides.

The lemon shark is found down to a depth of about 90 meters, but pups remain in shallow water for several years. Lemon sharks are known to withstand changes in salinity and can even be found in fresh water.

Little is known about this typically deep-dwelling species. Like their short-finned relative, longfin mako sharks prefer warmer water, but they are rareshaly encountered. Longfin mako sharks are known to be caught as bycatch in pelagic longline fisheries, though not as often as the shortfin mako. However, catches may be underestimated, since they are commonly misidentified as shortfin makos.

Nurse sharks are a bottom-dwelling, docile species found in a variety of habitats which include continental shelves, coral and rocky reefs, mangroves and sand flats. Nurse sharks are equipped with long barbells on their snout to locate benthic prey.

Found far from shore, the oceanic whitetip shark’s range spans entire oceans. Oceanic whitetips are now rarely seen, although previously considered one of the most widespread and abundant sharks. Oceanic whitetip sharks fall victim to the longlines and gillnets of commercial fisheries in the open ocean, both as a target and bycatch.

This seasonally migratory species has a stocky body and short snout. Porbeagle sharks are found around the world, but adjacent populations appear to be distinct. This species prefers colder waters and is, in fact, endothermic.

The porbeagle shark is caught as a target and bycatch species in commercial fisheries for its high-value meat. Directed longline fisheries seriously depleted the northeast Atlantic population and less than one percent of the Mediterranean population remains from a century ago.

The sandbar shark feeds primarily on small fish in the bottom of the water column and is considered harmless to humans. The species is found in a variety of marine habitats, ranging from very shallow intertidal waters to depths of 280 meters.

Sandtiger sharks are also known as the grey nurse shark and the spotted ragged-tooth shark. Sandtiger sharks have one of the lowest reproductive rates of any shark, giving birth to only one or two young every couple of years.

Once a population is depleted, recovery is especially challenging due to their life history. Smaller populations are also much more susceptible to disease.

The distinctive hammer-shaped head may provide improved maneuverability and increased sensory capacity for the scalloped hammerhead shark. A seasonally migratory species, the scalloped hammerhead is often found in schools.

Possibly the fastest shark and certainly one of the most active, the shortfin mako shark is only found in tropical and warm temperate seas. During summer months, shortfin makos follow patches of warm water. Shortfin mako sharks are both targeted by longline fisheries for their meat and caught incidentally as bycatch.

Small spotted catsharks have a light colored body with black spots from nose to tail. Adults often school by sex and eggs are deposited on seaweed throughout the year. Small spotted catsharks are caught primarily as bycatch or secondary targeted catch in various artisanal and industrial fisheries, especially in the Mediterranean.

The spiny dogfish, also known as the spurdog, is found within all of the world’s oceans. Spiny dogfish are caught for a variety of purposes which include: fish and chips, shark fin soup, fertilizers, liver oil, pet food and as a popular dissection specimen in academic science labs.

The whale shark is the world’s largest fish, with an average length of 14-20 meters. Yet, their diet consists of one of the ocean’s smallest organisms -- plankton. These filter-feeders can live to be 100 years old and may have up to 300 young per litter.