This study provides an assessment of Cormorant occupancy and impact at stillwater game fisheries in England and Wales, during 1988/89 to 1992/93. A total of 167 waterbodies operated as 'put-and-take' trout fisheries was included within a questionnaire survey, and this provided the bulk of the data used in the analyses. The results show that Cormorants are widespread at inland stillwater game fisheries in England and Wales throughout the year, with higher densities present during October-March. Peak counts by fishery managers at 45 of the fisheries increased by about 20% per year, regardless of season. Site use by Cormorants is investigated and the results imply that large, low altitude sites that are close to rivers in southern England are more likely to be used by these birds. The survey revealed that Cormorants are widely perceived by fishery managers to be responsible for significant economic losses through consumption and/or injury of stock fish. While this may be justified locally, we found no overall relationship between Cormorant density and anglers' catches of Rainbow Trout, the principal stock fish.
Callaghan, D. A., Kirby, J. S., Bell, M. C., & Spray, C. J. (1998). Cormorant Phalacrocorax carbo occupancy and impact at stillwater game fisheries in England and Wales. Bird Study, 45(1), 1-17. https://doi.org/10.1080/00063659809461074