Stocking success of newly hatched pike evaluated by radioactive strontium (85Sr) marking
The stocking of newly hatched pike Esox lucius labelled with radioactive strontium (85Sr) and later electrofishing of the same area was found to be a workable tool in assessing the success of pike stockings. 85Sr‐labelled individuals constituted 96% of the 0+year pike catch from late summer electrofishing in the stocked littoral areas of the heavily regulated Lokka Reservoir. The density of 0+year pike reached 2·1 individuals 100 m−2 in the stocked areas in comparison to 0·3 individuals 100 m−2 in the reference areas. In the three other stocked lakes the proportion of labelled pike in the catch ranged from 0 to 42% in late summer. The results suggest that pike stockings are profitable in filling empty or nearly empty 0+year pike habitats of regulated lakes or other waterbodies, where the natural reproduction of pike has declined due to human activities.