Fish in space: local variations of home range and habitat use of a stream‐dwelling fish in relation to predator density

Abstract

A key response of animals to local environmental variation is altered use of space, but studies simultaneously examining local variation in habitat use and space use are uncommon. We predicted that elevated abundance of avian predators would result in grayling Thymallus thymallus, a stream‐dwelling fish, using mesohabitats containing more cover, superimposed on seasonal changes in use of key resources (and hence space use) for functions such as reproduction. Using radio‐telemetry, the pattern of space and habitat use by 40 wild grayling was determined in neighbouring stream sections in relation to season and predator density. Grayling used different habitats between seasons, but displayed similar patterns of habitat use in adjacent sections. Although patterns of habitat use were stable between stream sections, space use was not. In two winter periods, grayling ranged significantly more widely where there were significantly greater densities of avian predators, especially cormorant, Phalacrocorax carbo. No such differences were apparent in summer when cormorants were absent, but experimental manipulation of predator densities was not possible, so results are correlative. Support for a predator effect is provided from significantly greater rates of injury, associated with avian beak scar marks, present on grayling from the section with highest avian predator densities, compared with adjacent sections with lower levels of avian predators. Unlike many studies of fish behaviour to elevated predation risk, in which fish make greater use of ‘refuge’ habitat, grayling exhibited wide‐ranging behaviour and high activity, possibly reflecting avoidance behaviour.

Radio‐telemetry shows differences in the behaviour of wild and hatchery‐reared European grayling Thymallus thymallus in response to environmental variables

“…thymallus , suggesting that they are able to recognize favourable conditions and react to changes in specific environmental factors effectively. As was recently observed by Lucas & Bubb (), wild T . thymallus adjust their activity to the elevated predation risk as well.…”

“…This study shows threshold behavioural response in wild T. thymallus, suggesting that they are able to recognize favourable conditions and react to changes in specific environmental factors effectively. As was recently observed by Lucas & Bubb (2014), wild T. thymallus adjust their activity to the elevated predation risk as well. This study also revealed behavioural deficits of hatchery-reared T. thymallus in the wild; hence, in attempts to conserve indigenous T. thymallus populations, restoration of habitat complexity and natural spawning should take precedence over stocking.…”

Ecologia Do Movimento Em Peixes De Riacho

“…Desde a década de 1950, porém, o assunto tem sido estudado por diversos autores, especialmente na América do Norte (e.g. Funk 1957, Crossman 1977, Todd & Rabeni 1989, Young 1996, Horton & Guy 2002, Lucas & Bubb 2014, que apontaram evidências de movimentos em peixes de riacho, embora apenas recentemente o tema tenha sido investigado na região Neotropical (e.g. Mazzoni & Iglesias-Rios 2012, Espírito-Santo et al 2016, Celestino et al 2017, Azevedo 2017, Barros 2017, Espírito-Santo et al 2018, Lima 2018, Mazzoni et al 2018, Henninger et al 2020, De Fries 2020.…”