Intensive and selective removal of large individuals by fishers can act as a pronounced directional selection force, leading to evolution towards smaller body sizes. In addition to evolutionary downsizing, fishing can also reduce size and growth variation among individuals. Preserving variability is important: a population harbouring variation is less susceptible to changing environments and catastrophic disturbances. For example, when food availability is low, individuals that grow slowly will survive while fast-growing individuals will starve. Therefore, populations that consist of individuals growing at different rates will be better off in fluctuating environments.