Fishing magnifies natural variations in numbers of fish, increasing the risk of population collapses.

Timothy Essington and his colleagues at the University of Washington in Seattle analysed at least 25 years' worth of data on 55 stocks of small fish such as sardines, herrings and anchovies that are preyed on by others. The population sizes of these species fluctuate naturally and widely over time. But the researchers found that when populations collapsed to less than 25% of their mean size, the stocks were more likely to have experienced exceptionally high fishing rates before the collapse than to have seen large natural variations in size.

Modelling the fish populations suggests that fishery management practices that do not respond quickly to dips in species numbers increase both the magnitude and frequency of natural population declines.

Proc. Natl Acad. Sci. USA http://doi.org/3hk (2015)