Data from: Behavioural and fitness effects of translocation to a novel environment: whole-lake experiments in two aquatic top predators

Translocation into a novel environment through common fisheries-management
practices, such as fish stocking, provides opportunities to study
behavioural and fitness impacts of translocations at realistic ecological
scales. The process of stocking, as well as the unfamiliarity with novel
ecological conditions and the interactions with resident fish may affect
translocated individuals, leading to alterations of behaviours and causing
fitness impacts. Our objectives were to investigate how aquatic
top-predators behaviourally establish themselves and compete with resident
individuals following introduction in a novel lake environment and to
investigate the resulting fitness consequences. Using high-resolution
acoustic telemetry, we conducted whole-lake experiments and compared the
activity, activity-space size and fate of translocated and resident
individuals in two model top predators, northern pike (Esox lucius, n =
160) and European catfish (Silurus glanis, n = 33). Additionally, we
compared the reproductive fitness of translocated and resident northern
pike. The experiment was conducted with large (adult) individuals of
different origins, resilient to predation, but subject to agonistic
interactions and competition with resident fish. Over a period of several
months, the translocated catfish exhibited consistently larger
activity-space sizes than resident catfish, but did not differ from
residents in activity and survival. The pike from one of the two
translocated origins we tested also showed elevated space-use, and both
translocated origins revealed higher mortality rates than their resident
conspecifics, indicating maladjustment to their novel environment. When
non-resident pike reproduced, they overwhelmingly produced hybrid
offspring with resident fish, indicating that introductions fostered gene
flow of non-native genes. Our study indicates that fish introductions
result in behavioural and fitness impacts even in large-bodied top
predators that experience low levels of natural predation risk.