Growth and Sex Ratio of Eels (Anguilla anguilla) of Known Age in Four Small Lakes in Southern Finland
✍ Scribed by J. Tulonen
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 54 KB
- Volume
- 75
- Category
- Article
- ISSN
- 1434-2944
No coin nor oath required. For personal study only.
✦ Synopsis
Data was collected from four lakes in southern Finland during [1981][1982][1983][1984][1985][1986][1987][1988]. Two of the lakes were stocked in 1967 and the others in 1978. Sampling was done with fyke nets and long-lines in the lakes but the most effective catching inethod was fixed eel-boxes in the outlets of the lakes. A total of 811 eels were caught. Eels were sexed by inorphological examination of the gonads and 25
were found to be males. Growth was studied by length and weight measurements, length backcalculations based on ground otoliths and also with tagging experiinents (a modified Carlin-tag). The largest males in the older age groups were niore than 50 cin long and weighed over 200 grams. The largest females were niore than 100 cin long and weighed over two kilograms. Growth variation was greatest in the high age groups in which the weight difference was almost tenfold. In younger age groups the largest females were two to three times heavier than the smallest individuals. I n males the difference was not so extreme. Backcalculated mean annual growth increments were found to be more than 100 rnrn in the youngest age groups in both sexes decreasing sharply after two years, especially in niales. I n the eels aged ten years and over the mean annual growth increment uas about 10 n i ~n in males and 30 inni in females. Tagging experiiiients gave poorer growth for every age group and in the age groups over ten years growth was in many cases negative.