Growth and Production of Yellow Eels and Glass Eels in Ponds

Abstract

AbstractTwo experiments (I and II) were performed in drainable ponds. Yellow eels Anguilla anguilla (L.) were stocked in early June at three biomasses: 10, 20 and 60 kg · ha−1 in experiment I; and 10, 20 and 40 kg · ha−1 in experiment II. The mean body weights were 27.0 and 24.2 g respectively. Glass eels were stocked only in experiment II at equal densities of 1600·ha−1. In both experiments each biomass of yellow eel was combined in a factorial design with three cyprinid communities differing in biomass and in species‐ and size‐composition. The ponds were drained in autumn. The final body weights at draining ranged from 25.9 to 63.6 g for yellow eel and from 3.9 to 8.8 g for glass eel. The final body weights of yellow eel and of glass eel decreased with increasing biomass of yellow eel. No significant relation was found between the bream Abramis brama (L.) biomass and the growth of eel. The growth rates of yellow eel and glass eel were positively correlated in experiment II. At higher biomasses of yellow eel the percentage females decreased slightly. The recapture rates of yellow eel in experiments I and II amounted to 69.4 ± 9.8 % and 92.2 ± 4.9% (mean ± sd) respectively. The lower recapture rates in experiment I were caused by the inappropriate draining technique used. The glass eels were recaptured with 75.0·5.6% efficiency. The maximum net production of yellow eel occurred at a biomass of 20–40kg·ha−1 and amounted to 19 kg·ha−1.