Key factor analysis to assess cormorant depredation on inland fisheries in the UK

Authors: Britton, J.R., Harvey, J.P., Cowx, I.G., Holden, T., Feltham, M.J., Wilson, B.R. and Davies, J.M.

Pages: 14-27

Abstract:

Studies on the impact of cormorant, Phalacrocorax sp., depredation on inland fisheries generally concentrate on the derivation of the number or biomass of fish removed by birds from the total fish density or biomass present. However, this does not provide a detailed assessment of impact as it rarely provides insight to how the actual species, size ranges and year classes of fish being depredated upon are affected. To achieve this, key factor analysis was developed to reveal the status of fish populations being affected by cormorant depredation and their status if depredation had not occurred. Key factor analysis at Holme Pierrepont Rowing Course, Nottingham, UK, showed cormorant depredation reduced the numbers of roach, Rutilus rutilus (L.), common bream, Abramis brama (L.), and perch, Perca fluvialtis L., by 62%, 51% and 65% respectively, and the biomass by 72%, 67% and 75% respectively. The cohorts of roach that dominated angler catches in 1998, i.e. the 1995 and 1996 year classes, were reduced by cormorant depredation by 75% and 65% respectively. The data highlighted that cormorant depredation reduced the availability of fish for angler exploitation in subsequent years.

Source: Scopus