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Sleep in fish. Sleep can be defined in birds and mammals by eye closure and typical electrical patterns in the neocortex, but fish lack eyelids and a neocortex. Yet this oscar is behaviorally quiescent at night, lying unresponsive on the bottom with its eyes turned downward, and might be said to sleep. [1]
The reason is the gonads fully mature in winter, but they are in dormant phase due to the low temperature, thus the fish spawn only on the returning favorable conditions in spring. [12] The rise of temperature in streams from near freezing to 10–17 °C (50–63 °F) during May – June induces common snowtrout to spawn. [ 14 ]
Aquatic locomotion. A great cormorant swimming. Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella. Swimming has evolved a number of times in a range of organisms including arthropods, fish, molluscs, amphibians, reptiles, birds, and mammals.
A grizzly bear ambushing a jumping salmon during an annual salmon run. A salmon run is an annual fish migration event where many salmonid species, which are typically hatched in fresh water and live most of the adult life downstream in the ocean, swim back against the stream to the upper reaches of rivers to spawn on the gravel beds of small creeks.
Oceanic fish inhabit the oceanic zone, which is the deep open water which lies beyond the continental shelves. Oceanic fish (also called open ocean or offshore fish) live in the waters that are not above the continental shelf. Oceanic fish can be contrasted with coastal fish, who do live above the continental shelf. However, the two types are ...
Shoaling and schooling. These powder blue tangs are shoaling. They are swimming somewhat independently, but in such a way that they stay connected, forming a social group. These bluestripe snapper are schooling. They are all swimming in the same direction in a coordinated way. In biology, any group of fish that stay together for social reasons ...
Fish locomotion. Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body and tail in the water, and in various specialised fish by motions of the fins.
Diel vertical migration (DVM), also known as diurnal vertical migration, is a pattern of movement used by some organisms, such as copepods, living in the ocean and in lakes. The adjective "diel" (IPA: / ˈdaɪ.əl /, / ˈdiː.əl /) comes from Latin: diēs, lit. 'day', and refers to a 24-hour period. The migration occurs when organisms move up ...