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Sharks are found in all seas. They generally do not live in fresh water, with a few exceptions such as the bull shark and the river shark which can swim both in seawater and freshwater. [99] Sharks are common down to depths of 2,000 metres (7,000 ft), and some live even deeper, but they are almost entirely absent below 3,000 metres (10,000 ft).
In Queensland, great white sharks found alive on the drum lines are shot. [173] In New South Wales, between 1950 and 2008, a total of 577 great white sharks were killed in nets. [169] Between September 2017 and April 2018, fourteen great white sharks were killed in New South Wales. [174]
The bull shark (Carcharhinus leucas), can swim between salt and fresh water, and are found in tropical rivers around the world. Some prehistoric sharks (in a broad sense), including hybodonts and xenacanths, are also thought to have inhabited freshwater environments.
The ISRA criteria take into account the complex biological and ecological needs of sharks. There are four criteria and seven sub-criteria. Important Shark and Ray Areas (ISRA) are discrete three-dimensional portions of habitat that are important for one or more species of chondrichthyans (sharks, rays and chimaeras) and have the potential to be managed for conservation. [1]
[48] [49] Tiger sharks have also been observed to feed on dead manta rays in the German Channel of Palau. [50] Evidence of dugong predation was identified in one study that found dugong tissue in 15 of 85 tiger sharks caught off the Australian coast. [51] Additionally, examination of adult dugongs has shown scars from failed shark attacks. [52]
Mackerel sharks, also called white sharks, are large, fast-swimming sharks, found in oceans worldwide. They include the great white, the mako, porbeagle shark, and salmon shark. Mackerel sharks have pointed snouts, spindle-shaped bodies, and gigantic gill openings. The first dorsal fin is large, high, stiff and angular or somewhat rounded.
The first shark-like chondrichthyans appeared in the oceans 400 million years ago, [1] developing into the crown group of sharks by the Early Jurassic. [2] Listed below are extant species of shark. Sharks are spread across 512 described and 23 undescribed species in eight orders. The families and genera within the orders are listed in ...
Bull sharks have occasionally gone as far upstream in the Mississippi River as Alton, Illinois. [32] Bull sharks have also been found in the Potomac River in St. Mary's County, Maryland. [33] [34] From 1996 to 2013, a golf course lake at Carbrook, Logan City, Queensland, Australia was the home to several bull sharks.