sentence: Shoals are more vulnerable to predator attack.
sentences_before: When schooling fish stop to feed, they break ranks and become shoals.
sentences_after: 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.
concept_name: shoal
headings: Shoaling and schooling Schooling
categories: Fish Ecology