December 14, 2016

The impact of piscivorous birds on freshwater fisheries

The impact of piscivorous birds on freshwater fisheries

Many freshwater fisheries of ecological and economic importance are in decline, while populations of piscivorous (fish-eating) birds such as goosanders and cormorants are increasing.

This has led to growing pressure from the angling community to control numbers of these birds, and it also poses a challenge to the designation and management of protected riverine areas where both predators and prey are integral components of the ecosystem. Licences to cull these otherwise protected bird species are currently issued where numbers are suggested to threaten the fishery; however, there are no data for assessing the impact of culling on either fish or bird numbers and the economic benefits remain undetermined.

Furthermore, efforts to understand the relationship between populations of freshwater fish and their avian predators are undermined by a lack of information about the daily and seasonal movements of birds between freshwater and marine environments. The breeding and feeding sites of birds counted at coastal winter roosts are unknown, as are the foraging ranges of freshwater breeders. Observations suggest that birds can be a localised problem, but there is no evidence that avian predation is driving declines in fish populations.

This project aims to: (1) combine the latest GPS tracking technology with stable isotope analyses to investigate the movements of goosanders and cormorants within and between coastal and freshwater environments; (2) quantify the diet of these birds from existing sample sources; (3) conduct bird surveys and behavioural observations to quantify seasonal variation in foraging behaviour; and (4) combine the results from (1)-(3) with national survey data to model population trends and the risk to fisheries.

The research combines challenging but exciting fieldwork using cutting-edge technology with sophisticated laboratory techniques and population modelling. Full training will be provided, giving the student a diverse skill set for a career in ecology or conservation.

We are looking for applicants with a strong interest in avian ecology and conservation, excellent ecological field experience and a willingness to work alongside a diverse range of partners and stakeholders. Applicants must also hold a minimum of a UK Honours degree at 2:1 level or equivalent in a relevant discipline and a valid driving licence. Bird ringing experience, relevant lab experience and mathematical modelling skills are all advantageous but not essential.

For further details please contact Dr Stuart Sharp ( or Dr Bart Donato (