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

Published source details Pedersen M.I., Jepsen N. & Rasmussen G. (2017) Survival and growth compared between wild and farmed eel stocked in freshwater ponds. Fisheries Research, 194, 112-116.
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This study is summarised as evidence for the following.

	Action	Category
	Release wild-caught captive-reared eels to re-establish or boost native populations ('head-starting') Action Link
	Translocate wild eels to re-establish or boost native populations (‘stocking’ or ‘restocking’) Action Link

Release wild-caught captive-reared eels to re-establish or boost native populations ('head-starting')

A replicated study in 2011–2012 at seven ponds in Denmark (Pedersen et al. 2017) found that wild-caught captive-reared European eels Anguilla anguilla were recaptured in greater numbers and grew faster than translocated wild eels, 12 months after release. In each of two experiments, average recapture rates after five months did not differ significantly between translocated wild-caught captive-reared eels (61–73%) and translocated wild eels (53–61%). However, after 12 months, in two ponds in one experiment, wild-caught captive-reared eels had greater recapture rates (66%) than wild eels (52%). Average increases in length over two growing seasons were greater for wild-caught captive-reared eels (1.1–12 cm) than wild eels (0.3–7 cm). In June 2011 and 2012, European eels (50 wild-caught and captive-reared; 50 wild) were tagged and released into each of 6–7 freshwater ponds (192–204 m²). Captive-reared eels (each 3–6 g) were captured in France during the winter before release and reared at a commercial eel farm. Wild eels (each 2–5 g) were captured in a trap at a hydropower station in Denmark. In one experiment, four ponds were drained after five months, and two ponds after 12 months. In the other experiment, all seven ponds were drained after five months. Eels were captured in nets as ponds were drained and weighed and measured in length.

(Summarised by: Anna Berthinussen)
Translocate wild eels to re-establish or boost native populations (‘stocking’ or ‘restocking’)

A replicated study in 2011–2012 in seven ponds in Denmark (Pedersen et al. 2017) found that translocated wild European eels Anguilla anguilla were recaptured in lower numbers and grew slower than wild-caught captive-reared eels, 12 months after release. In each of two experiments, average recapture rates after five months did not differ significantly between translocated wild eels (53–61%) and wild-caught captive-reared eels (61–73%). However, after 12 months, in two ponds in one experiment, wild eels had lower recapture rates (52%) than wild-caught captive-reared eels (66%). Average increases in length over two growing seasons were lower for wild eels (0.3–7 cm) than wild-caught captive-reared eels (1.1–12 cm). In June 2011 and 2012, eels (50 wild, 50 wild-caught and captive-reared) were tagged and released into each of 6–7 freshwater ponds (192–204 m²). Wild eels (each 2–5 g) were captured in a trap at a hydropower station in Denmark. Captive-reared eels (each 3–6 g) were captured in France during the winter before release and reared at a commercial eel farm. At the end of each experiment, eels were captured in nets as ponds were drained. In one experiment, four ponds were drained after five months, and two ponds after 12 months. In the other experiment, all seven ponds were drained after five months. All recaptured eels were weighed and measured.pon

(Summarised by: Anna Berthinussen)