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Changes in the Growth of Pike (Esox lucius) in Windermere
Journal of Animal Ecology
Vol. 52, No. 2 (Jun., 1983), pp. 647-657
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/4578
Page Count: 11
You can always find the topics here!Topics: Food supply, Gill nets, Animal ecology, Heat sums, Human cannibalism, Temperature, Freshwater fishes, Bones, Fish, Weather
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(1) Pike (Esox lucius L.) were sampled in Windermere every year from 1944 to 1982. Lengths-for-age of 11 775 fish were determined from the opercular bones. Ages ranged from 2 to 18 years. Pike aged 9 years and older formed 19% of the catch in 1944, 3%, 2% and 1% respectively in the 1950s, 1960s and 1970s. Three periods of different growth were identified: (a) the late 1940s and 1950s, (b) the early 1960s, (c) the late 1960s and 1970s. (2) Comparison of mean lengths at ages 1-4 years, males and females separately of year-classes hatched in 1943, 1953, 1963 and 1973 showed at each age, (a) no significant differences between 1943 and 1953 year-classes, (b) 1963 year-class significantly smaller than the other year-classes (with one exception), (c) 1973 year-class significantly larger than the other year-classes. (3) Growth was adequately described by von Bertalanffy's equation. Males had a smaller ultimate length than females, and their expected life-span was shorter. (4) Regressions of weight of females at age 4 years on cumulative temperature (degree days over 14 degrees C in the first 4 years of life) were: very significant for year-classes 1944-1978 and 1944-1959, and not significant for year-classes 1960-1965 and 1968-1978. (5) The main food of pike is perch (Perca fluviatilis L.). In the late 1940s and 1950s the food supply was sufficient for pike to respond to changes in temperature conditions by changes in growth. In the early 1960s the food supply was insufficient, growth was poor and was not correlated with temperature conditions. In the late 1960s and 1970s, food supply for young pike became limited probably due to the fast growth of perch, and it is likely that cannibalism became intensified. There were low numbers and high mean values for length and weight of pike. Growth was good and was not correlated with temperature conditions. (6) Prediction of pike growth in the 1960s and 1970s could not reasonably have been made on the basis of observed growth during the previous 20 years.
Journal of Animal Ecology © 1983 British Ecological Society