Long Term Stocking Efficiency of European Eel in Estonian lakes

The construction of the Ivangorod HPS in the early 1950s blocked totally the natural upstream migration of young eel from the Baltic Sea to the Narva River basin. Due to the rather permanent introduction of glass eels or farmed eels into L. Võrtsjärv (since 1956) and four small lakes (since 2003), it has become one of the most important commercial fish in this lakes. The stocking rate with glass eels in L. Võrtsjärv has been relatively low: annual average in 1956-2001 was about 35 ind.ha^-1yr^-1. The peak of stocking with glass eels occurred in the early 1980s (84 ind.ha^-1yr^-1). As a result the mean catch of eel constituting 2.5 kg ha^-1 yr^-1. The maximum catch of this fish in L. Võrtsjärv was recorded in 1988 (104 t or 3.7 kg ha^-1). According to reported catch data the recapture for glass eel was 3-6% and for farmed eel 10-15%. The natural status of eel stock before the construction of HPS was not very abundant (annual catch 1,8 tons L. Võrtsjärv and 3-6 tons L. Peipsi). According to tagging and recapture results HPS is not obstacle for downstream migration.