Windermere: Effects of Exploitation and Eutrophication on the Salmonid Community

• Published in: Journal of the Fisheries Research Board of Canada
• Main Authors: Cren, E. D. Le, Kipling, Charlotte, McCormack, Jean C.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1972
• Subjects: Anguilla anguilla; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f72-126; http://www.nrcresearchpress.com/doi/pdf/10.1139/f72-126

Windermere is a lake of 14 km 2 divided into two glacially excavated basins. It is essentially mesotrophic but, about 1840, Asterionella became the dominant planktonic diatom and small changes towards eutrophication have recently occurred, all as a result of increases in population, water borne sewage, and agricultural fertilization in the catchment.Windermere has five salmonid taxa belonging to the three species: Salmo salar, S. trutta, and Salvelinus willughbii. Perca fluviatilis, Esox lucius, Anguilla anguilla, and Phoxinus phoxinus are abundant, and there are two other small fish species.A successful net fishery for the char, perch, pike, and trout operated for several centuries until overfishing for the char and an ascending interest in sport fishing for salmon and trout brought it to an end in 1921. There was then no significant exploitation until 1941.The Freshwater Biological Association has experimented with the fish populations since 1941 by intensive trapping of perch from 1941 to 1964 and gillnetting of pike from 1944 to the present. Perch were reduced to less than 20% of their former abundance and have not recovered since trapping ceased; their growth rate has increased. The larger pike have been reduced but young pike are more numerous. Char have increased. Most of the population changes of these three species can be attributed to pike netting, but fluctuations caused by variations in year-class strength contribute.The recent establishment of small local populations of Rutilus rutilus, Scardinius erythrophthalmus, and Tinca tinca are probably the only effects on the fish of slight eutrophication.