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Spatial ecology of freshwater eels in South Africa: implications for conservation

Abstract

Four freshwater eel species (Anguilla spp.) occur in southern African rivers that are increasingly anthropogenically modified. Information on movements, habitat use and overlap by African eels is needed for their conservation. We carried out a preliminary investigation of the spatial ecology of three eel species in the Thukela River, South Africa, using radio-telemetry. Nineteen yellow-stage eels were surgically implanted with radio-tags, comprising A. mossambica (n = 2), A. bengalensis (n = 9) and A. marmorata (n = 8), and tracked from October 2018 to August 2019. Tagged eels exhibited high individual variability in space use. We recorded very small home ranges in winter for all species. A lack of apparent territoriality at inter- and intra-specific levels was observed. Eel species tended to use similar mesohabitats, especially glides, but habitat preference changed across seasons, and between species, suggesting fine-scale spatial and temporal niche partitioning. Given the breadth of flow typologies used by Thukela eels across the seasons, conservation of these long-lived species indicates that management of river flows needs to be sensitive to their habitat requirements all year round, but in many water-stressed South African rivers, this may be unlikely. Maintaining good habitat connectivity for these migrant species must be prioritised.

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Data Availability

Research data may be obtained from the lead author upon reasonable request. The code used for home range analysis (PHRE) has been developed by Max Tarjan and is freely available on GitHub (https://github.com/mtarjan/PHRE/blob/master/PHRE_eel.R).

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Acknowledgements

We are most grateful to Zingela Safari and River Company owners M. and L. Calverley and their staff for their support and hospitality during the study. We acknowledge the coding expertise offered by Dr M. Tarjan offered in applying the PHRE methodology. We acknowledge the dedication of two interns, S. Fetsch and T. von Seydlitz, as well as the advice offered by C. Dearden and B. Gijsbertsen. We are grateful to the reviewers for their constructive comments.

Funding

We thank Idea Wild (USA) for the donation equipment and the Ford Wildlife Foundation (ZA) for vehicle support. We thank the University of KwaZulu-Natal (ZA) and the National Research Foundation (ZA; Grant 98404) for funding.

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Correspondence to Colleen T. Downs.

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Hanzen, C., Lucas, M.C., O’Brien, G. et al. Spatial ecology of freshwater eels in South Africa: implications for conservation. Hydrobiologia 848, 2579–2593 (2021). https://doi.org/10.1007/s10750-021-04581-2

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  • DOI: https://doi.org/10.1007/s10750-021-04581-2

Keywords

  • Radio-telemetry
  • Anguilla
  • Home range
  • Habitat use
  • Water resource management
  • Rivers