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The fish have been exposed to higher levels of estrogen, leading to feminized fish. [27] Males display female reproductive organs, and both sexes have reduced fertility, and a higher hatch mortality. [28] Freshwater habitats in the United States are widely contaminated by the common pesticide atrazine. [29]
Fish vision shows adaptation to their visual environment, for example deep sea fishes have eyes suited to the dark environment. Fish and other aquatic animals live in a different light environment than terrestrial species. Water absorbs light so that with increasing depth the amount of light available decreases quickly.
It is common for fish to use more than one form of propulsion, although they will display one dominant mode of swimming [19] Gait changes have even been observed in juvenile reef fish of various sizes. Depending on their needs, fish can rapidly alternate between synchronized fin beats and alternating fin beats.
Some semi-aquatic mammals have adaptations for visions (larger eyes, tapetum) that allow them to see and potentially communicate using visual signals even in low light conditions. [14] In some fish, mantis shrimp and squid, their eyes have a specific photoreceptor structure/orientation that is thought to give them the ability to detect ...
Common coldwater fish include brook trout, rainbow trout, and brown trout. Coolwater fish species prefer water temperature between the coldwater and the long warmwater species, around 60 to 80 °F (16–27 °C). They are found throughout North America except for the southern portions of the United States.
A food web is network of food chains, and as such can be represented graphically and analysed using techniques from network theory. [1] [2] Classic food web for grey seals in the Baltic Sea containing several typical marine food chains [3] The fourth trophic level consists of predatory fish, marine mammals and seabirds that consume forage fish.
The American paddlefish is a highly derived fish because it has evolved specialised adaptations such as filter feeding. Its rostrum and cranium are covered with tens of thousands of sensory receptors for locating swarms of zooplankton, its primary food source.
The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ in bony fish (but not cartilaginous fish [1]) that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift via swimming, which expends more energy. [2]