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[1] [a] Although shoaling fish can relate to each other in a loose way, with each fish swimming and foraging somewhat independently, they are nonetheless aware of the other members of the group as shown by the way they adjust behaviour such as swimming, so as to remain close to the other fish in the group. Shoaling groups can include fish of ...
A bait ball, or baitball, occurs when small fish swarm in a tightly packed spherical formation about a common centre. [1] It is a last-ditch defensive measure adopted by small schooling fish when they are threatened by predators. Small schooling fish are eaten by many types of predators, and for this reason they are called bait fish or forage fish.
These fish are adapted for an active life under low light conditions. Most of them are visual predators with large eyes. Some of the deeper water fish have tubular eyes with big lenses and only rod cells that look upwards. These give binocular vision and great sensitivity to small light signals. [37]
Fish social behaviour called ‘shoaling’ involves a group of fish swimming together. This behaviour is a defence mechanism in the sense that there is safety in large numbers, where chances of being eaten by predators are reduced. Shoaling also increases mating and foraging success.
Billfish normally use their bills to slash at schooling fish. They swim through the fish school at high speed, slashing left and right, and then circle back to eat the fish they stunned. Adult swordfish have no teeth, and other billfish have only small file-like teeth. They swallow their catch whole, head-first.
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.
The central nervous system is confined to the lateral line and olfactory systems, the eyes are small and may not function, and gills, kidneys and hearts, and swim bladders are small or missing. [ 48 ] [ 55 ] These are the same features found in fish larvae , which suggests that during their evolution, bathypelagic fish have acquired these ...
Diagrammatic vertical section through the eye of teleost fish. Fish have a refractive index gradient within the lens which compensates for spherical aberration. [4] Unlike humans, most fish adjust focus by moving the lens closer or further from the retina. [5] Teleosts do so by contracting the retractor lentis muscle.