PHD Project

October 4, 2022

Impacts of non-native invasive crayfish in tropical freshwater systems


Invasive species are a key cause of biodiversity decline in freshwater systems. Crayfish are a particularly problematic invader, with multiple species ranked amongst the worst global invaders. However, relatively little is known about invasive crayfish in tropical rivers. There is also growing evidence that invasive crayfish can have both ecological and geomorphological impacts, which can be highly detrimental in combination. Untangling the relative impacts of the ecological and geomorphological disturbance caused by invasive species is critically important to predicting future impacts of invasive species and inform their management in freshwaters.

This project will involve field monitoring, field experiments and laboratory work to investigate the invasion of Malaysian and Singaporean rivers by the Redclaw Crayfish (Cherax quadricarinatus). Fieldwork, including environmental, taxonomic and eDNA sampling, will determine the distribution of crayfish within a tropical river basin, and potential environmental controls on their distribution. DNA metabarcoding analysis will allow an assessment of biological diversity and community composition at invaded and uninvaded sites. Evidence of impacts on river substrate and bank stability will be documented and related to sites of invasion. Crayfish will also be experimentally excluded from some areas of river to study the potential recovery of aquatic ecosystems and river processes. Finally, laboratory work will test the relative significance of the predatory and competitive impacts of Redclaw Crayfish in comparison to their disturbance of bed sediments.

The successful applicant will be trained in all necessary field, laboratory and analytical methodologies, working with academics in the UK, Malaysia and Singapore. Results from the work will inform management of invasive crayfish in Malaysian rivers, and invasion biology in tropical rivers more broadly.

The successful applicant will hold a minimum of a UK Honours Degree at 2:1 level, or equivalent, in a relevant subject area including Environmental Science, Natural Science, Bioscience, Bioinformatics, Physical Geography or Geosciences. Fieldwork experience is strongly desired. Experience in molecular laboratory work and data analysis is an asset.

The project may be undertaken on either a full- or part-time basis.

For further information about the studentship please e-mail Matthew Johnson ( or Alexandra Zieritz (