Increased population density of pike Esox lucius - a result of selective harvest of large individuals

The effect of selective harvest of large pike on number of middle-sized pike was tested in a small, eutrophic lake in SE Norway. The pike population was estimated using a mark-recapture method in two different periods: before (1980-1983) and during the manipulation of the pike population (2004-2006). After an extensive size selective harvest of large pike (>= 65 cm) in 2004, the number of pike in length-class 45-65 cm, mainly 3+ pike, increased significantly from 2004 to 2005. The number in this length-class was even higher in 2006. Since 2+ pike was part of the diet of large pike, the increase in number of 3+ pike in 2005 and 2006 is probably due to reduced consumption of 2+ pike, following the substantial selective removal of large pike in 2004 and 2005. To maintain a high annual survival of young pike, a selective exploitation of large pike has to be carried out annually.