Stocking experiments with 0+ eels (Anguilla anguilla L.) in Danish streams: Post-stocking movements, densities and mortality

During the last 30 yr there has been a decline in eel (Anguilla anguilla L.) populations and catches in Denmark. In 1987 and 1988 a series of stocking experiments were performed using eels of different sizes (0.3-1.1 g), stocking densities and stocking methods (spot versus scatter). Post-stocking movement and mortality were evaluated. Only minor movements were recorded in the first 2-3 months after stocking. Assessment of spot stocking suggests that post-stocking densites were in the range of natural densities and independent of number stocked; i.e. the density represents the carrying capaicty of the stream in question. The result suggests that spot stockings results in density-dependent mortality, which can be reduced by scatter-stocking. Daily mortality rates in the first 3 months after stocking ranged from 0.017 to 0.0233, 7-16 times greater than natural mortality.