Abstract
The yellowfishes of the Vaal River (Labeobarbus kimberleyensis and L. aeneus) are charismatic, socially and economically important fishes, but very little is known about their interspecies habitat preferences and movement. This study is the first behavioural study of yellowfish in the Vaal River using radio transmitters to characterise habitat preferences and movement patterns. A total of 22 adult L. kimberleyensis and 13 adult L. aeneus individuals were tracked for between 1 month and 1 year from 23 September 2006 to 16 May 2010. Radio telemetry revealed that yellowfish established routine daily behavioural patterns through which the habitat preferences and movement of the species could be established. Home ranges of the yellowfish ranged from 1 km to more than 12 km in the Vaal River depending on the species and habitat availability. Habitat preferences varied between species and included deep slow-flowing habitats with associated cover features particularly in winter for L. kimberleyensis and shallow fast-flowing habitats particularly for L. aeneus in spring, summer and autumn. Changes in flows, habitat availability and atmospheric pressure affected the movement of yellowfish. The biology and ecology of the yellowfish in the Vaal River is noticeably more complicated and dynamic than previously documented. We recommend that the behavioural ecology of these and other yellowfish populations in the Vaal River should continue to be characterised, and the use of the movement of yellowfish be developed as an indicator of ecosystem change.
Highlights
The yellowfish considered in this study showed high fidelity for sites ranging from less than 1 km for L. aeneus to 12 km for L. kimberleyensis
The reach of the Vaal River used by Labeobarbus spp. may be influenced by habitat requirements and availability, the differences in home range size may be associated with the roaming predatory nature of L. kimberleyensis and omnivorous foraging feeding biology of L. aeneus.[14,28,43,44]
The Vaal River yellowfishes have species-specific preferences for habitat types that differ among seasons, to other cyprinids,[40] indicating that considerable differences in the biology of the species exist
Summary
Knowledge of habitat use and associated requirements is needed to inform the management of fishes and the ecosystems in which they occur,[1,2] for economically important species.[2,3] Behavioural studies using movement as a variable have widely been used to evaluate the ecological consequences of changes in ecosystem conditions of both natural and anthropogenic origin.[4,5,6]The Orange-Vaal largemouth yellowfish Labeobarbus kimberleyensis (Gilchrist and Thompson, 1913), and the Orange-Vaal smallmouth yellowfish L. aeneus (Burchell, 1822) are charismatic fishes that have both social and economic value in the Orange-Vaal River system in southern Africa.[7,8] Both species are actively targeted by angling and subsistence fishing communities for food, and are used as indicator species in regional management and conservation plans.[8,9,10] The Vaal River Labeobarbus spp. and other large African cyprinids are slow-growing, late-maturing and long-lived fishes, and these features increase their vulnerability to anthropogenic activities.[11,12,13] Numerous water quality, quantity and habitat alteration impacts that negatively affect the biodiversity of the Vaal River have been identified.[10,14] Notwithstanding the highly degraded habitat in the Vaal River, L. aeneus is abundant while L. kimberleyensis is rare. Knowledge of habitat use and associated requirements is needed to inform the management of fishes and the ecosystems in which they occur,[1,2] for economically important species.[2,3] Behavioural studies using movement as a variable have widely been used to evaluate the ecological consequences of changes in ecosystem conditions of both natural and anthropogenic origin.[4,5,6]. Aspects of the biology and ecology of the Vaal River yellowfishes have been documented, their respective interspecies behavioural ecology, which is important to their management and conservation, is poorly known.[14] L. kimberleyensis is relatively rare and regarded as ‘Near Threatened’.13,16,17 aspects of the biology and ecology of the Vaal River yellowfishes have been documented, their respective interspecies behavioural ecology, which is important to their management and conservation, is poorly known.[14]
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