Density and yield of the noble crayfish Astacus astacus in the River Skotsbergelva, SE Norway
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Abstract
The population density and yield of the noble crayfish Astacus astacus was estimated on two localities in the River Skotsbergelva in the Halden river system, SE Norway, in August 1989. The estimated densities of catchable crayfish (>70 mm; caught in baited traps) varied between localities and with method of estimation. Mark - recapture estimates were much higher than comparable Leslie-estimates. Estimated densities varied from 0.47 to 0.93 crayfish m-2. Yield of legal size crayfish varied from 2.4 to 23.6 kg ha-1. Fishing mortality was estimated to 28 - 66%, being highest at the locality with the highest yield and exploitation.
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