Conventional calculations of virtual-population densities (fig. 7) of whitefish and perch (AG = I) in Lake Constance (Obersee) in October 1983 will not be possible before 1986. The results should then be compared with the present estimates based on the hydroacoustic survey in 1983.
A published prognosis (Hartmann, 1983a) of year - class strength does suggest a stock size of about 2.7 × 106 whitefish and 22 × 106 perch during the experiment. These numbers correspond to 900 t whitefish and 400 t perch.
This agrees quite well with the hydroacoustic estimate of 2.5 × 106 whitefish. We do not have enough hydroacoustic data on perch to estimate the stock size. However, in the Bregenzer Bucht we suggest a population of 3 × 106 perch.
As the shore area and the surface layer are not included in these hydroacoustic estimates, the population density will be higher in perch and to a less degree also in whitefish.
