Study

Survival and growth of European eels stocked as glass‐ and farm‐sourced eels in five lakes in the first years after stocking

  • Published source details Simon J. & Dörner H. (2014) Survival and growth of European eels stocked as glass‐ and farm‐sourced eels in five lakes in the first years after stocking. Ecology of Freshwater Fish, 23, 40-48.

Actions

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
Eel Conservation in Inland Habitats

Translocate wild eels to re-establish or boost native populations (‘stocking’ or ‘restocking’)

Action Link
Eel Conservation in Inland Habitats
  1. Release wild-caught captive-reared eels to re-establish or boost native populations ('head-starting')

    A replicated study in 20052010 at five lakes in Brandenburg, Germany (Simon & Dörner 2014) found that 8–17% of released wild-caught captive-reared European eels Anguilla anguilla survived after 3–6 years and were a similar size to translocated wild glass eels after 56 years. After 36 years, the percentage of eels surviving in each lake was estimated to be 817% for wild-caught captive-reared eels and 545% for translocated wild eels (difference not statistically tested). Five and six years after release, wild-caught captive-reared eels had similar average lengths (179347 mm) to translocated wild glass eels (186311 mm) in four of five lakes, despite being released at significantly larger sizes (average length: captive-reared = 165 mm; wild = 72 mm). In the other lake, too few eels were recaptured for analysis. Between 2004 and 2007, wild-caught captive-reared eels (55 eels/ha, average 7 g/eel) and translocated wild glass eels (200 eels/ha, average 0.3 g/eel) were released into each of five lakes (<20 ha) on two occasions in AprilJune. Eels were tagged and marked before release. Captive-reared eels were wild-caught in France as glass eels and reared at commercial eel farms. Wild glass eels were obtained from commercial fisheries in England. The lakes were previously stocked with farmed eels until 19972004. In May 20052009, each lake was sampled three times by electrofishing from a boat along the shoreline. Captured eels were identified, measured and weighed before being released. Survival rates were estimated from a mark and recapture experiment in AprilJune 2010.

    (Summarised by: Anna Berthinussen)

  2. Translocate wild eels to re-establish or boost native populations (‘stocking’ or ‘restocking’)

    A replicated study in 20052010 in five lakes in Brandenburg, Germany (Simon & Dörner 2014; same sites as Simon 2023) found that translocated wild European glass eels Anguilla anguilla reached a similar size to released wild-caught captive-reared eels after 56 years. Five and six years after release, translocated wild glass eels had similar average lengths (186311 mm) to wild-caught captive-reared eels (179347 mm) in four of five lakes, despite being released at significantly smaller sizes (average length: wild = 72 mm; wild, captive-reared = 165 mm). After 36 years, the percentage of eels surviving in each lake was estimated to be 545% for translocated wild eels and 817% for wild-caught captive-reared eels (difference not statistically tested). Between 2004 and 2007, translocated wild glass eels (200 eels/ha, average 0.3 g/eel) and wild-caught captive-reared eels (55 eels/ha, average 7 g/eel) were released into each of five lakes (<20 ha) on two occasions in AprilJune. Eels were tagged and marked before release. Wild glass eels were obtained from commercial fisheries in England. Captive-reared eels were wild-caught in France as glass eels and reared at commercial eel farms. The lakes were previously stocked with farmed eels until 19972004. In May 20052009, each lake was sampled three times by electrofishing from a boat along the shoreline. Captured eels were identified, measured and weighed before being released. Survival rates were estimated from a mark and recapture experiment in AprilJune 2010.

    (Summarised by: Anna Berthinussen)

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