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How does behaviour underpin the impact of invasive tilapia on native fish?

Project Description

Invasive species have a huge impact on the structure of freshwater communities and are a major source of biodiversity loss. Physiological, morphological and life history traits that are associated with invasive potential have been studied extensively. How invasive and native species interact through behaviour, however, has rarely been documented, particularly in aquatic habitats where observing behaviour is problematic. Aquaculture using Nile tilapia Oreochromis niloticus is growing exponentially throughout the tropics as an affordable source of animal protein; however, its spread is associated with feral populations becoming established outside its native range and subsequent negative effects on native fish assemblages. Many of these negative effects are hypothesised to be mediated by behaviour: Nile tilapia are believed to competitively exclude native fish from shelters (exposing native fish to greater predation risk), outcompete native fish for food, and their foraging behaviour reduces macrophyte algae abundance and increases water turbidity. Despite some evidence of these effects, e.g. from behavioural laboratory studies, observing and quantifying the extent to which they occur in natural systems has remained elusive.

This project will use artificial shelters equipped with underwater cameras in mesocosms and at field sites in Tanzania to quantify in unprecedented detail the interactions between Nile tilapia, an increasingly problematic invasive species in tropical freshwater ecosystems, and native cichlid fish species. Artificial shelters will provide a greater standardisation of monitored areas, and act as local hotspots of activity between fish species that use shelters where a representative proportion of behavioural interactions can be recorded. Competition for food will also be quantified by experimentally presenting food at these artificial shelters. eDNA (environmental DNA) and local catch records of fisheries will be used to identify sites that have been colonised by the Nile tilapia, and these will be paired with control sites that are ecologically similar and geographically close but where Nile tilapia are currently absent. Local catch records will also be used to identify the other fish species present, alongside an eDNA metabarcoding approach based on mitochondrial 12S sequences and a bespoke reference library that will be created based on existing samples. The project will provide training from a world-class supervisory team with strong track records in each of their fields: molecular methods (eDNA, by Genner), designing optimal shelters and recording set ups (by Ioannou and Genner), quantifying behavioural interactions from video (by Ioannou and Thornton), and advanced statistical data analysis (by Ioannou). Training in fieldwork and fish species identification in Tanzania will be provided by Tamatamah and Genner, who will also supervise and facilitate engagement with local stakeholders including fisheries managers and governmental policy makers.

Although more difficult to study, behaviour is potentially very important in invasive species biology as behaviour is often more flexible and adaptable than other traits. This challenging project will develop a new approach to monitoring behaviour underwater, shining new light on the very real-world threat posed by invasive species in aquatic environments. Such data can then be used to improve risk assessment models which generally ignore behavioural interactions.

Dr Alex Thornton (Exeter University) and Dr Rashid Tamatamah (Tanzania Fisheries Research Institute (TAFIRI)) are also supervisors on this project.

Funding Notes

The project will suit a candidate wanting to work at the intersection of ecology, cognition and behaviour, interested in a project that applies basic research in behaviour to a major threat to biodiversity (invasive species). Motivation to work independently for long periods in tropical field conditions is essential.

Applicants must have a minimum of a 2:1 bachelor honours degree in Biology or a similar subject

How good is research at University of Bristol in Biological Sciences?

FTE Category A staff submitted: 64.60

Research output data provided by the Research Excellence Framework (REF)

Click here to see the results for all UK universities

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