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The shape a shoal or school takes depends on the type of fish and what the fish are doing. Schools that are travelling can form long thin lines, or squares or ovals or amoeboid shapes. Fast moving schools usually form a wedge shape, while shoals that are feeding tend to become circular.
Pods of many dolphin species commonly herd a school of fish into a bait ball while individual members take turns ploughing through and feeding on the more compacted shoal. Corralling is a method where fish are chased to shallow water where they are more easily captured.
Fish derive many benefits from shoaling behaviour including defence against predators (through better predator detection and by diluting the chance of capture), enhanced foraging success, and higher success in finding a mate. [106] It is also likely that fish benefit from shoal membership through increased hydrodynamic efficiency. [107]
Fish derive many benefits from shoaling behaviour including defence against predators through better predator detection and by diluting the chance of capture, enhanced foraging success, and higher success in finding a mate. It is also likely that fish benefit from shoal membership through increased hydrodynamic efficiency.
In oceanography, geomorphology, and geoscience, a shoal is a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body of water close to the surface or above it, which poses a danger to navigation. Shoals are also known as sandbanks, sandbars, or gravelbars.
Shoaling behavior improves foraging success, because the demand for anti-predatory activities per individual is reduced and because more individuals scanning for food leads to quicker detection. In general, a larger shoal of fish locates food faster, which was confirmed to be true in common minnows.
This can be seen in species of shoaling fish, where the initial aggregation of individuals to a group initially allowed for the protection from predators, however the limiting resources available changes over time, and mortality rates of these fish begin to increase, [31] showing that resource competition is an important regulator of reef fish ...
In the presence of predatory stimuli, a banded killifish individual will prefer the bigger conspecific shoal, but only as long as the shoal is homogenous in individual fish size. If the size of individual fish were different, they would join a shoal of similarly sized fish regardless of shoal size. This preference is maintained by predatory threat.