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Forage fish: Forage fish occupy central positions in the ocean food webs. The organisms it eats are at a lower trophic level, and the organisms that eat it are at a higher trophic level. Forage fish occupy middle levels in the food web, serving as a dominant prey to higher level fish, seabirds and mammals. [28] Predator fish; Ground fish
Salmon sharks get their name from their diet, which primarily consists of salmon. It is known for its ability to maintain stomach temperature ( homeothermy ), [ 4 ] which is unusual among fish. This shark has not been demonstrated to maintain a constant body temperature.
All sharks and rays are cartilaginous fish, contrasting with bony fishes. Many rays are adapted for feeding on the bottom. Many rays are adapted for feeding on the bottom. Guitarfishes are somewhat between sharks and rays, displaying characteristics of both (though they are classified as rays).
The basking shark (Cetorhinus maximus) is the second-largest living shark and fish, [4] after the whale shark. It is one of three plankton-eating shark species, along with the whale shark and megamouth shark. Typically, basking sharks reach 7.9 m (26 ft) in length.
In US waters, the 1993 Fishery Management Plan for Sharks of the Atlantic Ocean sets an annual quota of 92 tons (after processing) for the porbeagle. [53] In 2006, this species was listed as a species of concern by the NMFS, meaning that it merits conservation concern, but data are insufficient for inclusion on the US Endangered Species Act. [65]
Like other fish, sharks extract oxygen from seawater as it passes over their gills. Unlike other fish, shark gill slits are not covered, but lie in a row behind the head. A modified slit called a spiracle lies just behind the eye, which assists the shark with taking in water during respiration and plays a major role in bottom–dwelling sharks.
A spiracle is a small hole found behind each eye. These can be tiny and circular, such as found on the nurse shark (Ginglymostoma cirratum), to extended and slit-like, such as found on the wobbegongs (Orectolobidae). Many larger, pelagic species, such as the mackerel sharks (Lamnidae) and the thresher sharks (Alopiidae), no longer possess them.
They are heavily built sharks, sometimes weighing nearly twice as much as sharks of comparable length from other families. Many in the family are among the fastest-swimming fish. Megachasmidae: Megamouth sharks: 1 1 The megamouth shark is an extremely rare species of deepwater shark, and the smallest of the three filter-feeding sharks.