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

Overall effectiveness category Evidence not assessed
Number of studies: 15
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Background information and definitions

Wild-caught anguillid eels (usually glass eels or elvers) may be translocated from one site to another to re-establish or augment declining native populations (often referred to as ‘stocking’ or ‘restocking’). This action involves directly releasing translocated wild eels at new sites following transportation from capture sites. Releases of captive-reared individuals may also be done, in which case wild-caught eels are reared for some time in captivity (‘head-started’) before they are released back into the wild. See ‘Release wild-caught captive-reared eels to re-establish or boost native populations (‘head-starting’)’. These actions typically involve releasing translocated eels in different water catchments to where they were captured. Wild anguillid eels may also be captured and transported around obstacles within water catchments to aid upstream migration, for example glass eels and elvers may be caught in rivers downstream of dams and released immediately upstream. See ‘Threat: Natural system modification – Capture and transport eels around dams/barriers (‘trap and transport’).

For studies that compare the effects of different methods for translocating anguillid eels, such as length of quarantine period or stocking density, see ‘Change capture, transport or release methods to increase survivorship of translocated (‘stocked’ or ‘restocked’) eels’.

Note that translocated eels are typically monitored through mark and recapture, but different methods of marking or tagging can influence recapture rates, or even survival, of translocated eels (Josset et al. 2016, Kullman et al. 2018, Jepsen et al. 2022).

^{Jepsen N., Richter L., Pedersen M.I. & Deng Z. (2022) Survival, growth and tag retention of juvenile European eel (Anguilla anguilla L.) with implanted 12 mm passive integrated transponder tags and acoustic tags. Journal of Fish Biology, 101, 135–1380. https://doi.org/10.1111/jfb.15183}

^{Josset Q., Trancart T., Mazel V., Charrier F., Frotte L., Acou A. & Feunteun E. (2016) Pre-release processes influencing short-term mortality of glass eels in the French eel (Anguilla anguilla, Linnaeus 1758) stocking programme. ICES Journal of Marine Science, 73, 150–157. https://doi.org/10.1093/icesjms/fsv074}

^{Kullmann B., Hempel M. & Thiel R. (2018) Chemical marking of European glass eels Anguilla anguilla with alizarin red S and in combination with strontium: In situ evaluation of short-term salinity effects on survival and efficient mass-marking. Journal of Fish Biology, 92, 203–213. https://doi.org/10.1111/jfb.13508}

Study locations

Key messages

Fifteen studies evaluated the effects of translocating wild anguillid eels to re-establish or boost native populations (‘stocking’ or ‘restocking’). Five studies were in Canada, two in Germany, and one in each of New Zealand, Austria, Sweden, Denmark, Belgium, Portugal, the USA and France.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (13 STUDIES)

Abundance (7 studies): Three of five studies (including one replicated and one before-and-after study) in New Zealand, Canada, Denmark, Belgium and France found that at least half of wild European eels (50–85%) translocated to a river or ponds were recaptured 5–12 months or 4–8 years after release. The other two studies reported low recapture rates of wild American eels (0.01%) and wild longfin eels (4%) translocated to a river system or lake up to five or ten years after release. One of the studies found that 12 months after release, translocated wild European eels were recaptured in lower numbers than wild-caught captive-reared eels. One study in Austria found that catch rates of wild European eels translocated to six lakes declined over 25 years after release. One study in the USA found that catch rates of wild American eels translocated to a river increased for the first four years after release, and then decreased for another four years.

Survival (2 studies): Two replicated studies in Germany found that less than half of wild European eels (5–45%) translocated to lakes survived for 3–6 years after release. One of the studies reported similar survival rates for eels released in winter and spring.

Condition (9 studies): Four studies in Canada, Austria, Portugal, and the USA found that wild American and European eels increased in size after translocation. In one of the studies, eels released at a downstream river site increased in size more than those released upstream. Two replicated studies in Germany and Denmark found that 5–6 years after release, translocated wild European eels were a similar size, but grew faster, compared to wild-caught captive-reared eels. Two studies in Canada found that, compared to naturally occurring American eels, translocated wild eels were smaller in size and had smaller egg cells or had faster growing females, a higher percentage of males, and matured and migrated at smaller sizes. One before-and-after study in New Zealand found that wild longfin eels grew faster and were in better condition after they were translocated compared to before.

BEHAVIOUR (7 STUDIES)

Movement (7 studies): Three of four studies (including one before-and-after study) in Canada, Belgium, Portugal and the USA found that translocated wild American and European eels dispersed from release sites to multiple areas of a lake or upstream and downstream in a river. The other study found that most translocated wild American eels remained near release sites in a river after eight years. Two studies in Sweden and Canada found that translocated wild American and European eels followed a similar migration route at a similar speed to naturally occurring eels. However, one of the studies detected a higher proportion of translocated eels migrating to the ocean than naturally occurring eels. One study in Canada found that translocated wild eels migrated at smaller sizes than naturally occurring eels.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A before-and-after study in 1998 and 2008 in a lake in Otago region, New Zealand (Beentjes & Jellyman 2015) found that translocated wild longfin eels Anguilla dieffenbachii were recaptured in low numbers, and they grew faster and were in better condition than before translocation. Of 2,010 translocated, tagged eels, 79 (4%) were recaptured 10 years later. During 10 years after release, translocated eels grew at faster rates (average 3.7 cm/year) and were in significantly better condition (data reported as condition factor) than before translocation (average 2.4 cm/year). Growth rates increased after translocation and remained high for 4–5 years before declining (see paper for details). On average, eels were larger after 10 years (total length: 77 cm, body mass: 1,462 g) than before translocation (42 cm, 173 g), although the difference was not statistically tested. In February 1998, approximately 9,500 juvenile longfin eels were caught by commercial fishers in the tidal reaches of a river. Captured eels were transported 200 km upstream to a lake, of which 2,010 were tagged, weighed and measured before release. During one night in 2008, 399 eels were recaptured in fyke nets by a commercial eel fisher, 79 of which (all females) had tags. Condition, length and body mass were measured for all 79 recaptured tagged eels. Otoliths were examined for 76 recaptured tagged eels to determine changes in growth rate.
Study and other actions tested
Referenced paper
Beentjes M.P. & Jellyman D.J. (2015) Growth patterns and age validation from otolith ring deposition in New Zealand longfin eels Anguilla dieffenbachii recaptured after 10 years at large. Journal of Fish Biology, 86, 924-939.
A study in 2009 in a lake and adjoining river in Ontario, Canada (Pratt & Threader 2011) reported that translocated wild American eels Anguilla rostrata dispersed and increased in length and weight. Results are not based on tests of statistical significance. Translocated eels were recaptured or observed at six locations within the lake (40–300 km from release sites, total 253 eels) and at one location in the river (30 km downstream of release sites, total 88 eels). The average length and weight of translocated eels increased between spring and autumn in both the lake (spring: 131 mm, 3 g; autumn: 147 mm, 6 g) and river (spring: 172 mm, 12 g; autumn: 291 mm, 53 g). Wild American eels were translocated to five sites in a lake (1.3 million glass eels in 2008–2009) and five sites in an adjoining river (167,000 elvers in 2006, 2.6 million glass eels in 2007–2009). Eels were obtained from a commercial fishery, and were quarantined and marked before release. In spring and autumn 2009, boat electrofishing was carried out at night along transects (100-m long, 2.5-m wide) in the lake (28–33 transects) and river (42–44 transects). Captured eels (lake: 144 eels, river: 28 eels) were measured and weighed. Size was estimated for eels observed from the boat (lake: 109 eels, river: 60 eels).
Study and other actions tested
Referenced paper
Pratt T.C. & Threader R.W. (2011) Preliminary evaluation of a large‐scale American eel conservation stocking experiment. North American Journal of Fisheries Management, 31, 619-628.
A replicated study in 2005–2010 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 5–6 years. Five and six years after release, translocated wild glass eels had similar average lengths (186–311 mm) to wild-caught captive-reared eels (179–347 mm) in four of five lakes, despite being released at significantly smaller sizes (average length: wild = 72 mm; wild, captive-reared = 165 mm). After 3–6 years, the percentage of eels surviving in each lake was estimated to be 5–45% for translocated wild eels and 8–17% 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 April–June. 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 1997–2004. In May 2005–2009, 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 April–June 2010.
Study and other actions tested
Referenced paper
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.
A study in 1984–2010 in six alpine lakes in Salzkammergut, Austria (Essl et al. 2016) found that translocated wild European eels Anguilla anguilla increased in length and weight, but catch rates declined. During three time periods over 25 years, translocated eels increased in average total length (1984–1989: 45 cm; 1998–1999: 57 cm; 2009–2010: 66 cm) and weight (1984–1989: 178 g; 1998–1999: 353 g; 2009–2010: 548 g). However, over the same time periods, average catch rates of translocated eels declined (1984–1989: 115 eels/h; 1998–1999: 29 eels/h; 2009–2010: 11 eels/h). In 1954–1981, a total of 180,000–2,200,000 glass eels were translocated to each of six previously eel-free lakes (area: 3–46 km², average depth: 12–90 m). Eels were sampled in each of the six lakes in May–October during 2–3 time periods (1984–1989, 1998–1999, 2009–2010). Electrofishing was carried out by boat along the shore at 1–46 sites/lake for 0.25–6 h/site. Captured eels were weighed and measured.
Study and other actions tested
Referenced paper
Essl K., Gassner H., Schabetsberger R., Jagsch A. & Kaiser R. (2016) The development of stocked eels (Anguilla anguilla) in previously eel‐free Austrian Alpine lakes. Ecology of Freshwater Fish, 25, 17-26.
A study in 1997–2010 in a river system and estuary in Ontario, Canada (Couillard et al. 2014) found that translocated wild American eels Anguilla rostrata were smaller in size and had smaller egg cells (oocytes) than naturally occurring eels. Translocated wild eels had lower body mass (313–752 g) and length (531–781 mm) than naturally occurring eels (1,163–3,276 g, 824–1,173 mm). Additionally, translocated wild eels had smaller oocytes (diameter 0.21–0.29 mm) than naturally occurring eels (0.22–0.35 mm). Eye size, pectoral fin size and muscle lipid content were lower in translocated eels compared to naturally occurring eels, but digestive tract mass and water content were higher (see paper for details). In 2005–2010, approximately 6.8 million glass eels purchased from commercial fisheries on the coast were tagged and translocated 900–1,100 km to either Richelieu River or St. Lawrence River and Lake Ontario. In 1997–2001, wild juvenile eels (319–582 mm) captured on eel ladders on two dams in the St. Lawrence River were tagged and released upstream of the dams. In September–November 2010, translocated wild eels and naturally occurring eels were recaptured at the St. Lawrence Estuary by commercial fishers (using weirs at angles to the shoreline) during their seaward migration. Measurements from 51 translocated and 51 naturally occurring eels were compared.
Study and other actions tested
Referenced paper
Couillard C.M., Verreault G., Dumont P., Stanley D. & Threader R.W. (2014) Assessment of fat reserves adequacy in the first migrant silver American eels of a large‐scale stocking experiment. North American Journal of Fisheries Management, 34, 802-813.
A study in 2010–2011 in a river system in Ontario, Canada (Reid & Hogg 2014) found that translocated wild American eels Anguilla rostrata were recaptured in low numbers in half of the tributaries sampled within the river system. In total, 476 of four million translocated eels (0.01%) were recaptured along seven of the 13 tributaries within the river system up to five years after release. No eels were recaptured in the other six tributaries. Recaptured translocated eels had dispersed upstream to distances of 22–45 km in five tributaries with passable dams, and 3–5 km in two estuaries with impassable dams. In 2006–2010, four million translocated wild glass and elver American eels (142,000–2,000,000 eels/year, average length 57–61 mm) were released at two locations in Lake Ontario and the St. Lawrence River. Eels were obtained from a commercial fishery in Novia Scotia and New Brunswick. In September–October 2010 and June–October 2011, each of 154 sites along 13 tributaries of the river system were surveyed once. At each site, boat or backpack electrofishing surveys were carried out along eight (50-m long) or 40 (10 x 1 m) transects, respectively. Translocated eels were distinguished from native eels by length. 
Study and other actions tested
Referenced paper
Reid S.M. & Hogg S. (2014) Reinforcement of American eel Anguilla rostrata populations in eastern Lake Ontario tributaries, Ontario, Canada. Conservation Evidence, 11, 29-33.
A study in 2010–2012 in a fjord in Grundsund, Sweden (Westerberg et al. 2014) found that translocated wild European silver eels Anguilla anguilla followed a similar migration route at a similar speed to naturally occurring eels. There was no significant difference in the migration speed of eels translocated from the UK (19–26 km/day) compared to eels naturally occurring in Sweden that had been translocated from a lake to a site downstream along their migration route (26–27 km/day). Both eel groups migrated along a similar route from the Swedish coast to the Sargasso Sea. Silver eels were captured from two rivers in Sweden: the River Enningdal, where eels were naturally occurring, and the River Ätran, where glass eels had been translocated, mostly from the UK, since 1983. Eels were captured using silver eel or Wolf traps. Eels were surgically tagged, released in the Gullmaren fjord in October 2010, and their migration monitored for two years. Ten translocated and seven naturally occurring eels retained their tags and could be analysed.
Study and other actions tested
Referenced paper
Westerberg H., Sjöberg N., Lagenfelt I., Aarestrup K. & Righton D. (2014) Behaviour of stocked and naturally recruited European eels during migration. Marine Ecology Progress Series, 496, 145-157.
A study in 2009–2011 in a river system in Ontario, Canada (Stacey et al. 2015) found that translocated wild American eels Anguilla rostrata had faster growing females, a higher percentage of males, and matured and migrated at smaller sizes compared to naturally occurring eels. On average, female translocated eels grew faster at ages 2–3 years (90–120 mm/year) than naturally occurring eels (53–56 mm/year). Growth rates did not differ significantly at ages one (101 vs 87 mm/year) and four years (53 vs 47 mm/year). A greater percentage of males were captured for translocated eels (40–52%) than naturally occurring eels (0%). Migrating translocated eels were reported to be shorter in length (average 651 mm) than naturally occurring eels (average 940 mm), although the difference was not tested for statistical significance. In 2005–2010, approximately 6.8 million glass eels captured in rivers by commercial fishers in Nova Scotia and New Brunswick were translocated to three sites in the river system. Eels were quarantined and marked before release. In May and September 2009–2011, translocated eels were captured during electrofishing surveys at two of the release areas. Naturally occurring eels were collected from an eel ladder at a power station. Captured eels (68 translocated, 96 naturally occurring) were weighed and measured, and a sample euthanized to determine age and sex. Migrating eels (191 translocated, 1,277 naturally occurring) were captured in the estuary of the river system by commercial fishers.
Study and other actions tested
Referenced paper
Stacey J.A., Pratt T.C., Verreault G. & Fox M.G. (2015) A caution for conservation stocking as an approach for recovering Atlantic eels. Aquatic Conservation: Marine and Freshwater Ecosystems, 25, 569-580.
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
Study and other actions tested
Referenced paper
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.
A study in 2011–2014 in a river system in Ontario, Canada (Béguer-Pon et al. 2018) found that a greater proportion of translocated wild American eels Anguilla rostrata were detected escaping to the ocean than naturally occurring eels, but migration speeds were similar. Overall, a greater proportion of translocated wild eels were detected escaping from the river system to the ocean (20%, 27 of 134 tagged eels) than naturally occurring eels (4%, 6 of 138 tagged eels). Average migration speeds did not differ significantly between translocated (22–39 km/day) and naturally occurring eels (22–42 km/day). In spring 2005–2010, approximately seven million glass eels and elvers were captured in coastal regions and translocated to two lakes connected to the river system. In September–November 2011–2014, silver eels (134 translocated, 138 naturally occurring) were captured migrating downstream, tagged with acoustic transmitters, and released. In 2011–2014, tagged eels were detected by acoustic receivers (154–186 receivers/year) deployed across a channel connecting the river system to the ocean. Migration speeds were calculated for 46 eels (27 translocated, 16 naturally occurring, three origin not reported).
Study and other actions tested
Referenced paper
Béguer-Pon M., Verreault G., Stanley D., Castonguay M. & Dodson J.J. (2018) The migration of stocked, trapped and transported, and wild female American silver eels through the Gulf of St. Lawrence. Canadian Journal of Fisheries and Aquatic Sciences, 75, 2024-2037.
A study in 2014–2017 in a river in southern Belgium (Nzau Matondo et al. 2019) reported that most tagged, translocated wild European eels Anguilla anguilla survived, dispersed from the release site and grew in size. During four years after release, 205 of 241 tagged, translocated eels (85%) were detected in the river. Detections were made up to 0.5 km downstream and 2.3 km upstream of the release site, although dispersal was limited by physical obstacles (see paper for details). Forty-seven translocated wild eels recaptured 1–3 years after release grew in length (average 31 mm/year). In 2013, wild glass eels (total 4,155 eels) were released in the Mosbeux River, 0.04 km upstream of its mouth. From November 2014 to September 2016, translocated eels recaptured along a 3-km stretch of the river during nine electrofishing sessions (using 40 x 40 cm diameter hand nets) were measured, radio-tagged, and released. Recaptured tagged eels were re-measured. Tagged eels were tracked 1–3 times/month (total 53 days) from December 2014 to May 2017.
Study and other actions tested
Referenced paper
Nzau Matondo B., Séleck E., Dierckx A., Benitez J., Rollin X. & Ovidio M. (2019) What happens to glass eels after restocking in upland rivers? A long‐term study on their dispersal and behavioural traits. Aquatic Conservation: Marine and Freshwater Ecosystems, 29, 374-388.
A study in 2014–2016 in a river in central Portugal (Félix et al. 2020) reported that translocated wild European eels Anguilla anguilla dispersed upstream and grew in length and weight. After six months, translocated wild eels had dispersed at least 3.6 km upstream of release sites. Overall, translocated eels increased in length by an average of 41–42 mm/year. Eels at the site furthest downstream had greater average increases in length (48–59 mm/year) and weight (2.1–6.9 g/year) than those at two sites upstream (29–45 mm/year; 1.5–2.3 g/year). In April 2014, glass eels were released at three sites (18,200–21,750 eels/site) along a 9.5-km stretch of river with eight low-head weirs. Eels were obtained from a fishery in a river in Portugal, and acclimatized before release. No eels were recorded in the river during surveys in March–April 2014 before translocation. Backpack electrofishing was carried out in sampling areas (≥100-m long) at each of the three release sites, and an additional site upstream, every three months from April 2014 to April 2015 and in April 2016. Recaptured eels were measured, weighed and released.
Study and other actions tested
Referenced paper
Félix P.M., Costa J.L., Quintella B.R., Almeida P.R., Monteiro R., Santos J., Portela T. & Domingos I. (2021) Early settlement and growth of stocked European glass eels in a fragmented watercourse. Fisheries Management and Ecology, 28, 91-100.
A replicated, site comparison study in 2012–2019 in a river in Pennsylvania, USA (Newhard et al. 2021) reported that translocated wild American eels Anguilla rostrata fluctuated in abundance, but increased in size and remained near release sites for eight years after release. Results are not based on tests of statistical significance. Relative eel abundance at release sites increased for the first four years after release (year one: 35 eels/h, year four: 65 eels/h), then decreased for another four years (year 8: 20 eels/h). Average eel length increased from 243 to 434 mm over eight years after release. Of 229 recaptured eels, 276 (99%) remained near release sites, while three (1%) were recaptured upstream, away from the release sites. A total of 118,742 glass eels and elvers were caught in the wild (location not provided) and released at two sites in a river from 2010–2013. Each year in 2012–2019, eels were caught via electrofishing at four sites close to release sites. In 2017–2019, electrofishing was carried out at 12 sites in the upper watershed of the river. Captured eels were counted, measured and released at the site of capture. Individual eels (200–300 mm long) were tagged before release. Relative abundance was calculated from catch rates (eels/h).
Study and other actions tested
Referenced paper
Newhard J.J., Devers J., Minkkinen S. & Mangold M. (2021) Assessment of reintroduction of American eel into Buffalo Creek (Susquehanna River, Pennsylvania). Journal of Fish and Wildlife Management, 12, 422-433.
A study in 2008–2015 in two ponds in a marsh in Camargue, France (Panfili et al. 2022) reported that tagged, translocated wild European eels Anguilla anguilla were recaptured at a rate of 50%. Over eight years after release, 2,437 of 4,909 tagged, translocated wild eels (50%) were recaptured one to five times. The growth rate of recaptured translocated eels was extremely variable among eel stages (yellow or silver) and size (see paper for details). In 2007, a total of 1,091 yellow eels were captured from a nearby brackish lagoon, tagged and released into two connected freshwater ponds (5.5–6.0 ha, average depth: 25–50 cm) in a 20.5 ha marsh. Each year from 2008 to 2012, glass eels (8,900–12,000 eels/year) were obtained from a river delta and released into the same ponds. All eels were placed in a freshwater tank before release. For nine consecutive days each year from 2008 to 2015, eels were recaptured using fyke nets, anaesthetised, measured and released. Unmarked, recaptured eels (originating from glass eels, total 3,818 eels) were tagged before release.
Study and other actions tested
Referenced paper
Panfili J., Boulenger C., Musseau C. & Crivelli A.J. (2022) Extreme variability in European eel growth revealed by an extended mark and recapture experiment in southern France and implications for management. Canadian Journal of Fisheries and Aquatic Sciences, 79, 631-641.
A study in 2010 and 2020–2021 in five lakes in Brandenburg, Germany (Simon 2023; same sites as Simon & Dörner 2014) reported that less than half of translocated wild European glass eels Anguilla anguilla released in winter survived for 3–4 years, and survival rates were similar to translocated wild eels released in spring. Results are not based on tests of statistical significance. After 3–4 years, the percentage of eels surviving in each lake was estimated to be 19–45% for translocated eels released in winter and 9–45% for translocated eels released in spring. During winter in February 2017, translocated wild glass eels (370 eels/ha, average 0.3 g/eel) were released in five lakes (each <20 ha, water temperatures 1–5°C). Eels were tagged and marked before release. In April–June 2020 and 2021, eels were recaptured by electrofishing from a boat along the entire shoreline on 6–8 occasions/lake. Data were compared to previously published survival estimates for translocated wild eels released at the lakes in spring 2006 and 2007 (200 eels/ha, average 0.3 g/eel; water temperatures 6–18°C), and recaptured in April–June 2010.
Study and other actions tested
Referenced paper
Simon J. (2023) Do glass eels restocked in winter have a lower survival rate than glass eels restocked in spring? Fisheries Research, 266, 106784.

Please cite as:

Cutts V., Berthinussen A., Reynolds S.A., Clarhäll A., Land M., Smith R.K. & Sutherland W.J. (2024) Eel Conservation in Inland Habitats: Global evidence for the effects of actions to conserve anguillid eels. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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This Action forms part of the Action Synopsis:

Eel Conservation in Inland Habitats

Related Actions

	Actions	Effectiveness	Studies	Category
	Translocate wild eels to re-establish or boost native populations (‘stocking’ or ‘restocking’) Action Link	Evidence not assessed	15	Synopsis Link
	Remove and relocate eel species before onset of impactful activities Action Link	No evidence found (no assessment)	0	Synopsis Link