Effect of an intensive mechanical removal effort on a population of non‐native rainbow trout Oncorhynchus mykiss in a South African headwater stream |
| |
| Authors: | Jeremy Shelton Olaf Weyl Johannes Van Der Walt Sean Marr Dean Impson Kristine Maciejewski Donovan Tye Helen Dallas Karen Esler |
| |
| Institution: | 1. Centre for Invasion Biology, Stellenbosch University, South Africa;2. Department of Conservation Ecology and Entomology, Stellenbosch University, South Africa;3. Freshwater Research Centre (FRC), Cape Town, South Africa;4. South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, South Africa;5. Centre for Invasion Biology, SAIAB, Grahamstown, South Africa;6. CapeNature Scientific Services, Stellenbosch, South Africa;7. Organisation for Tropical Studies, Skukuza, South Africa;8. Percy FitzPatrick Institute, University of Cape Town, Cape Town, South Africa;9. Nelson Mandela Metropolitan University, Port Elizabeth, South Africa |
| |
| Abstract: | - Invasions by non‐native species can compromise the conservation value of otherwise pristine headwater streams. While both developed and developing countries recognize this threat, few of the latter have suitable budgets to implement control programmes.
- This study assessed the effectiveness of a mechanical project to remove non‐native rainbow trout Oncorhynchus mykiss from a 6 km section of the upper Krom River, a small headwater stream in the Cederberg Mountains in South Africa's Cape Floristic Region (CFR).
- From October 2013 to February 2014, 354 O. mykiss were removed by angling (58%), fyke netting (28%) and gill netting (14%). This resulted in a marked reduction, but not eradication, of the O. mykiss population (fish relative abundance decreased from 0.53 ± 0.09 fish per net per night in October 2013 to 0.21 ± 0.09 fish per net per night in February 2014). Following the cessation of manual removals, the relative abundance of O. mykiss had increased to 0.56 ± 0.18 fish per net per night by March 2016, suggesting that without sustained removal effort, the population will rapidly return to its pre‐removal abundance level.
- Further work is needed to refine the methodology and test the effectiveness of mechanical removal of non‐native freshwater fish in a variety of ecological settings in the CFR. This approach holds potential for meeting the dual goals of reducing the ecological impacts of non‐native fishes and generating employment opportunities in line with the policy objectives of developing nations.
|
| |
| Keywords: | alien species fish mechanical removal restoration river stream |
|
|
