Temporal movement of free-swimming fishes and their response to environmental variables in some of the rivers of Kruger National Park, South Africa

The increase in anthropogenic stress on river ecosystems is of growing concern globally as demand for water increases and freshwater ecosystem degradation occurs. Understanding how the species respond to these stressors is important to manage ecosystem functioning, the conservation of species and the ecosystem services they provide. We used radio telemetry to determine the temporal movement of 19 tigerfish Hydrocynus vittatus and 11 lowveld large-scale yellowfish Labeobarbus marequensis, and their responses to environmental factors in two river systems, the Crocodile and the Olifants-Letaba rivers in the Kruger National Park, South Africa, from September 2011 to January 2012 and May 2018 to December 2019, respectively. Remote telemetry techniques were used to collect data from activity sensors attached to fish. Activity (movement count per hour) from both species showed diurnal behaviour. The data analyses using generalised mixed models with random effects showed that both species responded similarly to environmental factors, with differing significance in this response. Flow was negatively correlated, and water temperature positively correlated to activity. Both variables consistently showed higher significant responses than the other environmental variables assessed. Both fish species’ relationship to changes in flow and temperature can contribute to managing anthropogenic stressors and regulating flows in rivers. Further studies of this would significantly contribute to conserving these and other fish species in Kruger National Park. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.