Compensatory responses of fish populations in a shallow eutrophic lake to heavy depredation pressure by cormorants and the implications for management

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

Pages: 170-183

Abstract:

Through their protection under EU law, cormorant numbers have increased markedly on inland waters in the UK and the rest of Europe since the 1980s, although numbers have stabilised in recent years. It is believed that cormorant depredation has resulted in a deleterious impact on the freshwater fish populations of some inland fisheries, although few data have been able to prove this. This chapter describes the impact of intense cormorant depredation on the fish populations of Holme Pierrepont Rowing Course, Nottingham, between 1995 and 1998. Cormorant depredation allegedly reduced the fish stocks in the winter of 1993/1994, resulting in poor angling catches in the 1994 World Angling Championship. Despite subsequent, heavy depredation by over-wintering cormorants recorded in this study, the fish populations compensated for the losses incurred by cormorants by accelerating their growth rate. This minimised the size window when they were most vulnerable to depredation, lowered their age of sexual maturity and increased their fecundity for age. This ensured long-term sustainability in the fish populations in the face of the depredation and was due to a decrease in inter- and intra-specific competition in the fish populations. The implications of this on the management of fish populations subject to cormorant depredation are discussed.

Source: Scopus