Perch (Perca fluviatilis) and Pike (Esox lucius) in Windermere from 1940 to 1985; Studies in Population Dynamics

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Abstract
The aduit population of perch (Perca fluviatilis) in Windermere was severely reduced by an experimental trap fishery from 1941 to 1947 in one basin and from 1941 to 1964 in the other and has been monitored since. A gillnet fishery for pike (Esox lucius) >550 mm began in 1944 and has continued since. Changes in numbers, recruitment, mortality, growth, biomass, and fecundity have been measured. Summer water temperature and population density affected perch growth; temperature affected pike growth from 1944 to 1959, but not thereafter. A model involving correlations with temperature and negative correlations with abundance of adult perch and 0 group pike explained 90% of variation in perch recruitment for part of the period. Pike recruitment was correlated with temperature. In perch adult mortality rate and growth rate are correlated. Perch numbers are recovering after a 98% adult mortality from disease in 1976. Temperature and size-related predation within and between the two species appear to be the main controlling factors, but the relationships have changed from one part of the period to another.