Habitat preferences and movement of adult yellowfishes in the Vaal River, South Africa

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. Study areaThe study was carried out in a reach of the middle Vaal River, southwest of Johannesburg (Figure 1). The study area is located within the Orange-Vaal River Yellowfish Conservation and Management Association (OVRYCMA) area. Site selection was based on local OVRYCMA member information, historical catch records for yellowfish, historical data 5 and initial field surveys to ascertain the presence of sufficient adult yellowfish individuals for the study. The approximately 190-km reach of the Vaal River selected for the study extends from Parys to an area upstream of Bothaville (Figure 1). Within this reach, both L. kimberleyensis and L. aeneus are abundant, 4 despite disturbances such as water abstraction for agriculture, industry and mine use, wastewater releases and the use of natural products. Habitat diversity was considered to be representative of the middle reach of the Vaal River and included a high diversity of both deep (>3 m) and shallow areas (<1 m) with slow-(0 m/s) and fast-flowing (1 m/s) biotope types. Although some gauging weirs and other barriers that may affect the movement of yellowfish exist in the study area, all of the yellowfish monitored in the study had access to relatively large reaches of the Vaal River (>35 km).

Assessing the effect of tagging and the vulnerability to predation in tigerfish (Hydrocynus vittatus, Castelnau 1861) in a water-stressed system using telemetry methods

“…This deterioration has been attributed to several factors, including river fragmentation, flow modification, pollution, the introduction of alien species and global climate change (De Moor 1996;Ellender & Weyl 2014;O'Brien et al 2019). Fish make use of the available physical habitat as refugia, for feeding and spawning, and as nurseries for their offspring (Godin 1997;O'Brien et al 2013). Maintaining these environments is essential, but they are often inaccessible and difficult to sample, making observations hard to determine (Hussey et al 2015;Lennox et al 2017).…”

One Hundred Pressing Questions on the Future of Global Fish Migration Science, Conservation, and Policy

“…Conflicting literature regarding the migration behavior and distances traveled of the largemouth yellowfish (Labeobarbus kimberleyensis) suggests that studies may need to focus on detailing their behavior and the internal and external drivers of their migrations. The yellowfish are just one example of the many fish species in southern Africa that are sensitive to the increasing impacts of development, most notably from instream barriers (O'Brien et al, 2013). Without the necessary information on the migratory behavior of these freshwater fishes, water managers are not able to implement the necessary measures required to mitigate issues arising from development.…”

First observation of fouling of externally attached radio transmitters in an African river

“…In southern Africa, external radio tags to monitor freshwater fish movement behaviour are increasingly being used in a range of environmental monitoring, conservation and research programmes (O'Brien et al, 2012;O'Brien et al, 2013;Burnett et al, 2018;Roux et al, 2018;Burnett et al, 2020). External radio tags are generally preferred over surgically implanted transmitters as the latter have been shown to cause 100% mortality or tag loss in a Namibian reservoir (Økland et al, 2003).…”

“…External radio tags are generally preferred over surgically implanted transmitters as the latter have been shown to cause 100% mortality or tag loss in a Namibian reservoir (Økland et al, 2003). To date, however, there have been no studies on the possible effects of external radio transmitters, nor has there been a recapture of any radio-tagged fish (Eva et al, 2005;Økland et al, 2005;Thorstad et al, 2005;O'Brien et al, 2012;O'Brien et al, 2013;Jacobs et al, 2016;Burnett et al, 2018;Roux et al, 2018;Burnett et al, 2020) that could provide evidence of potential negative effects of using this method.…”