Interactions between fish and angler behaviour affect species-specific catchability of sympatric native charr and two introduced trout

Abstract

Catchability is a key determinant of fishing pressure, and plays an important role in the management of recreational fisheries. We investigated the catchability of three sympatric salmonid species in a recreational fishery in Lake Shikaribetsu, Japan—the endemic Miyabe charr (Salvelinus malma miyabei), introduced masu salmon (Oncorhynchus masou), and introduced rainbow trout (O. mykiss)—using a combination of stock assessment and angler survey data. Catchability differed among species, angling gear, and the interaction between these two, even when a similar fishing gear was used. Because of its migratory behaviour and fishing gear restrictions, the catchability of Miyabe charr was the lowest of these species, which became lower as fish density was lower. Conversely, the density-dependent changes of the catchability were not detected in masu salmon which few anglers targeted specifically. Rainbow trout catchability by fly anglers was the highest, possibly because the fishing tactics of fly anglers targeting this species were tailored to its foraging behaviour. We regarded differences in catchability among these three salmonids to be related to differences in fish and angler behaviours. These results indicate that behavioural characteristics of both fish species and anglers can cause different fishing pressure in a single recreational fishery targeting multispecies fish via interspecific catchability, and they should be taken into account for their management.