Survival and growth compared between wild and farmed eel stocked in freshwater ponds

摘要

To evaluate the efficiency of eel stocking, we compared the survival and growth of wild eels (2-5 g) with that of "farmed" eels (3-6 g). Wild eels were caught in a river and fanned eels came from a farm, where wild imported glass eels are cultured. Two experiments of 5-12 month duration were conducted in a series of shallow, open ponds of approximately 200 m(2). Wild and farmed eels were batch tagged, mixed and released in the ponds at an initial density of 0.5 individual/m(2). Survival was rather high (34-88%) with variations between ponds. No significant difference in survival was found between wild and fanned during the first 5 month in both experiments. Growth rates were significantly higher for fanned eels compared to wild eels in both experiments. The results show that farmed eels performed better than wild eels. In regions with low recruitment the eel population may be increased by importing glass eels, stocked directly or stocked as on-grown farmed eel. The optimal size for stocking (between glass- and 3 g eels) may be determined through future studies.