Species that are taken tends to relate to availability; in rivers with game fish 34% of their diet can be salmonids, whereas on other rivers eels are frequently taken as they are relatively easily predated. Mink can be a particular problem both with small collections of fish and at commercial fisheries. In a recent survey of commercial fisheries in Wales, for example, 30% reported that mink were a problem, despite only 50% having mink in their area. Although mink prefer smaller fish they do take larger fish and predation on individual high value fish can lead to a significant cost for fisheries and individuals.
A range of other foods are taken infrequently; these include frogs, snakes, beetles, earthworms and molluscs. Crayfish seem to be a favoured food and may be heavily predated where they are found, which may be an additional threat to the threatened native white-clawed crayfish.