The effect of prey identity and substrate type on the functional response of a globally invasive crayfish

Josie South*, Monica Mccard, Dumisani Khosa, Lubabalo Mofu, Takudzwa C. Madzivanzira, Jaimie T.A. Dick, Olaf L.F. Weyl

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
8 Downloads (Pure)


Biological invasions threaten biodiversity on a global scale, therefore, developing predictive methods to understand variation in ecological change conferred is essential. Trophic interaction strength underpins community dynamics, however, these interactions can be profoundly affected by abiotic context, such as substrate type. The red swamp crayfish (Procambarus clarkii) has successfully invaded a number of freshwater ecosystems. We experimentally derive the Functional Response (FR) (density dependent predation) of the red swamp crayfish preying upon both a benthic prey; chironomid larvae, and a pelagic prey; Daphnia magna, on a no substrate control, sand, and gravel substrates to determine whether (1) there is a higher impact on prey that are benthic, and (2) whether the presence of different substrate types can dampen the interaction strength. We apply and demonstrate the utility of the Functional Response Ratio (FRR) metric in unravelling differences in ecological impact not obvious from traditional FR curves. Procambarus clarkii is capable of constantly utilising high numbers of both benthic and pelagic prey items, showing a Type II functional response under all scenarios. The presence of gravel and sand substrate each independently decreased the magnitude FR upon D. magna. Though, with regards to chironomid larvae the FR curves showed no difference in magnitude FR, the FRR reveals that the highest impact is conferred when foraging on sand substrate. This reinforces the need for impact assessments to be contextually relevant.

Original languageEnglish
Pages (from-to)9-24
Number of pages16
Publication statusPublished - 07 Nov 2019

Bibliographical note

Funding Information:
We acknowledge the infrastructure and equipment provided by the NRF-SAIAB Research Platform and the funding channelled through the NRF-SAIAB Institutional Support system as well as the support received through the National Research Foundation-South African Research Chairs Initiative of the Department of Science and Technology (Inland Fisheries and Freshwater Ecology, Grant No. 110507). We thank the Queen's University Marine Laboratory for use of laboratory facilities and a running grant.

Publisher Copyright:
© Josie South et al.

Copyright 2020 Elsevier B.V., All rights reserved.


  • Aquatic invasions
  • Functional response ratio
  • Invader impact
  • Macroinvertebrates
  • Procambarus clarkii
  • Substrate

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology
  • Animal Science and Zoology
  • Ecological Modelling
  • Plant Science
  • Insect Science

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