Abstract
Egg strands of perch in Lake Geneva, Switzerland, during the spawning seasons of 1984, 1985 and 1986 were laid by the strong 1982 cohort. The abundance of these strands decreased from 1984 to 1986, whereas their modal size increased. These trends were used to estimate the decreasing abundance of the 1982 cohort and its increasing age. According to these data, total mortality within the 1982 cohort was 99% between the egg stage and 2 years, 78% between 2 and 3 years, 82% between 3 and 4 years.