Publication Abstract

Habitat use by roach (Rutilus rutilus L.) and perch (Perca fluviatilis L.) in response to the presence of Cormorants (Phalacrocorax Carbo L.) and artificial refuges.

Habitat use by roach (Rutilus rutilus L.) and perch (Perca fluviatilis L.) in response to the presence of cormorants (Phalacrocorax carbo L.) and artificial refuges

I.C. Russell, D. Goldsmith, A.C. Cook and D. Parrott

The rise in cormorant numbers in England and Wales over recent years and the increasing use of inland feeding sites has increasingly brought these birds into conflict with freshwater fisheries. This has highlighted the need for effective management measures that will reduce the interaction between these predators and their prey, and hence the level of cormorant impact on fish stocks and fisheries. One technique that is considered to have some potential in recreational coarse fisheries is the deployment of artificial refuges. The rationale behind this approach is that fish are particularly vulnerable to cormorants over the winter period when natural refugia (e.g. aquatic vegetation) are most limited, when water temperatures and hence fish swimming speeds are lowest, and when cormorant numbers at inland sites are highest. It is envisaged that the installation of artificial refuge structures to provide secure ‘holding areas’ might reduce the level of interaction between cormorants and their prey.

The behaviour of acoustically tagged roach and perch was assessed at a small stillwater coarse fishery in Norfolk, eastern England, using an acoustic positioning system. The aim of the investigation was to investigate habitat use by the fish, determine the extent to which natural and artificial refuges were utilised, and assess whether behaviour was affected by the presence of cormorants. The study also investigated whether cormorant foraging behaviour was influenced by the presence of the artificial refuges. Both roach and perch exhibited diurnal patterns of habitat use, tending to favour the margins by day and open water at night. However, this behaviour appeared to be modified by cormorant presence, with fish spending significantly more time in open water when birds were absent. Neither species utilised the introduced artificial refuge structures to any great extent and cormorant foraging behaviour did not differ significantly with and without the refuges present. The findings are discussed in the context of using refuges as a potential management technique for reducing the impact of cormorants at coarse fisheries.

Reference:

I.C. Russell, D. Goldsmith, A.C. Cook and D. Parrott (2005) 2005) Habitat use by roach (Rutilus rutilus L.) and perch (Perca fluviatilis L.) in response to the presence of Cormorants (Phalacrocorax Carbo L.) and artificial refuges. In:  M.T. Spedicato, G. Lembo & G. Marmulla (eds.). Aquatic telemetry: adavances and applications. Proceedings of the fifth conference on fish telemetry held in Europe. Rome FAO/COISPA. 2005. 295pp.

I.C. Russell*, D. Goldsmith*, A.C. Cook*, D. Parrott, J. Allcock & J. Barry

M.T. Spedicato, G. Lembo & G. Marmulla (eds.). Aquatic telemetry: adavances and applications. Proceedings of the fifth conference on fish telemetry held in Europe. Rome FAO/COISPA. 2005. 295pp.