The whitefish (Coregonus lavaretus (L.)) of the Wahnbach reservoir and their assessment by hydroacoustic methods |
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| Authors: | Dr T Brenner Dr J Clasen Dr K Lange T Lindem |
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| Institution: | (1) Landesanstalt für Fischerei Nordrhein-Westfalen, Heinsbergerstrasse 51-53, D-5942 Kirchhundem 1-Albaum, Federal Republic of Germany;(2) Wahnbachtalsperrenverband, Postfach 27, D-5200 Siegburg 1, Federal Republic of Germany;(3) Bundesforschungsanstalt für Fischerei, Institut für Fangtechnik, Palmaille 9, D-2000 Hamburg 50, Federal Republic of Germany;(4) Institute of Physics, University of Oslo, Blindern, P. O. Box 1048, Oslo 3, Norway |
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| Abstract: | In 1957 whitefish were successfully introduced into Wahnbach reservoir, a drinking water storage near Bonn (FRG). Since excessive
predation on the herbivorous zooplankton by fish could have negative effects on water quality, the size of the pelagic fish
stock had to be known. For this purpose, and for establishing management guidelines for the whitefish population, a stock
assessment involving hydroacoustics, trawling and gillnetting was performed in October 1984. The results indicate that the
whitefish stock is self-sustaining today. Growth of individual fish is moderate. The total pelagic fish population was estimated
to 11,130 fish, comprising some 2600 whitefish larger than 25 cm. Stock density was found to be low. An annual catch of about
900 adult whitefish (300 or 1.4 kg ha−1) is recommended in order to control population size and to limit predation pressure on the herbivorous zooplankton. |
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