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The Length-Weight Relationship and Seasonal Cycle in Gonad Weight and Condition in the Perch (Perca fluviatilis)

E. D. Le Cren
Journal of Animal Ecology
Vol. 20, No. 2 (Nov., 1951), pp. 201-219
DOI: 10.2307/1540
Stable URL: http://www.jstor.org/stable/1540
Page Count: 19
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Length-Weight Relationship and Seasonal Cycle in Gonad Weight and Condition in the Perch (Perca fluviatilis)
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Abstract

1. The methods of analysing length-weight data from fish are reviewed. Emphasis is laid on empirical formulae of the type W = aLn, and the limitations of the conventional condition factor. 2. The length-weight relationship of perch of all sizes was determined from a series of regressions of log weight on log length, and an analysis of covariance. Relative condition factors were calculated for individual fish from smoothed mean weights obtained from the regression lines. 3. In length-weight relationship it was found that the perch could be divided into a series of six groups corresponding with age, sex and maturity. Each group was generally homogeneous within itself throughout the seasons, but usually differed significantly from the other groups. Relative condition was found to vary significantly with the season. 4. At any one season the gonad weight is a constant percentage of the body weight for fish of all sizes. The seasonal changes in gonad weight are described and differ somewhat for the two sexes. Stomach contents weigh up to 2% of the body weight in summer. 5. There is a regular seasonal cycle in condition which is at its maximum in September and minimum in early spring. The different seasonal changes in condition between mature and immature fish can largely be accounted for by the cycle in gonad weight of the former.

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