The stock and yield of the European eel, Anguilla anguilla (L.), in large lakes of Estonia

Abstract

As a result of stocking since 1956, eel has become the most important commercial fish in L. Võrtsjärv (270 km2) today. Downstream migration of eel from L. Võrtsjärv supports eel fishery in L. Peipsi (3555 km2). The aim of this study was to assess the effectiveness of eel stocking in L. Võrtsjärv. The annual mean catch of eel and stocking rate and frequency were analysed by five- year periods. The stocking of eel in L. Võrtsjärv (annual average 35 ind. ha–1 in 1956–2001, maximum 84 ind. ha–1 in 1980–84) is below optimum rate, which explains the relatively low catches (annual average 1.2 kg ha–1 in 1965–2001, maximum 3.7 kg ha–1 in 1988, according to official statistics). The average number of glass eels required to produce 1 kg of eel catch (efectiveness of stocking) was about 32 in 1965–2001. A significant positive relationship (r = 0.41, p = 0.03, n = 28) was found between the stocking rate and the catches of eel in the sixth year after stocking. Eels caught from L. Võrtsjärv are larger (usually 60–80 cm) than those caught from other water bodies in Europe. Food competition between eel and the indigenous benthophagous fishes bream and ruffe is an important factor influencing the success of eel fishery in the lake.