Comparison of growth and condition of European eels stocked as glass and farm sourced eels in lakes in the first 4 years after stocking

Simon, Janek; Dörner, Hendrik; Scott, Richard; Schreckenbach, K.; Knösche, R.

doi:10.1111/jai.12078

Cited by 33 publications

(43 citation statements)

References 36 publications

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“…Farm eels may need adaptation time to use natural food (Simon et al 2013) during which they consume less food and fewer prey types compared with wild fish as described by other fish species (Sosiak et al 1979;Ersbak & Haase 1983;Sundstr€ om & Johnsson 2001). Furthermore, it cannot be excluded that non-or slowgrowing eels were sorted out in the eel farms after size grading and subsequently sold as stocking material.…”

Section: Stocking Form Lakementioning

confidence: 99%

“…Annual length increments under different environmental factors, age and size class were estimated for naturally recruited elvers as 38-91 mm, stocked elvers as 51-83 mm and stocked farm eels as 25-65 mm (Bisgaard & Pedersen 1991;Pedersen 1998;Lin et al 2007;Simon et al 2013). Furthermore, the recapture of cultured eel was lower than of wild eel in a river and a lake 1 and 7 years after stocking (Bisgaard & Pedersen 1991;Pedersen 2000).…”

Section: Introductionmentioning

confidence: 99%

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

Simon

Dörner

2013

Ecology of Freshwater Fish

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European eels Anguilla anguilla stocked as wild-sourced glass eels showed a better overall performance of growth and survival compared with farm-sourced eels after stocking in five isolated lakes within a 7-year study period. Eels stocked as farm eels lost their initial size advantage over eels stocked as glass eels within 3-5 years after stocking. Population sizes estimated for consecutive stocking batches indicated that 8-17% of eels stocked as farm eels survived 3-6 years after stocking compared with 5-45% of eels stocked as glass eels. This study coupled with results of previous studies suggests that stocking of farm eels may have no advantage in growth and survival compared with stocking of glass eels if stocking occurs at an optimal time in spring. In addition, the use of relatively expensive farm eels may provide no general advantage over stocking of glass eels. However, if glass eels are only available for stocking purposes very early in the year, lower survival rates than obtained in the present study can be assumed and stocking with relatively more expensive farm eels could possibly be a better option.

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Section: Stocking Form Lakementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Simon

Dörner

2013

Ecology of Freshwater Fish

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“…The low recapture rate is a general problem on glass eel studies (Simon and Do¨rner, 2014) and the catch rate rises with increasing age and size (Naismith and Knights, 1990;Lambert et al, 1994;Simon et al, 2013). The number of stocked glass eels recaptured by electrofishing 1 year following stocking at elver stage was low in the three streams probably due to this issue of small amount of glass eel stocked, the size of the individuals (median length, 9 cm) and the low efficiency of electric fishing for this life stage.…”

Section: Discussionmentioning

confidence: 99%

“…The annual length increases and survival rates in the stocked eels vary strongly between the stocking environments, the stocking materials (farm and glass eels), the stages (smaller and larger eels) and times after stocking (Bisgaard and Pedersen, 1991;Pedersen, 1998;Lin et al, 2007;Simon et al, 2013;Simon and Do¨rner, 2014). In stocked (Pedersen, 2009;Simon et al, 2013) and non-stocked (Naismith and Knights, 1990;Lambert et al, 1994) eels, the recapture rates improved with increasing age and size. In most studies, the combination of deep environments with the small size of glass eel make recaptures ineffective and complicate the monitoring of restocked individuals (Lambert et al, 1994), especially the first year after stocking.…”

Section: Introductionmentioning

confidence: 99%

“…Tributaries, lakes and ponds with low or no natural immigration have been stocked using glass eels and elvers caught in river estuaries (Walter, 1910;Mu¨ller, 1975;Klein-Breteler et al, 1990;Simon et al, 2009) and farm eels (Wickstro¨m et al, 1996;Pedersen, 1998Pedersen, , 2000Pedersen, , 2009Simon et al, 2013). The annual length increases and survival rates in the stocked eels vary strongly between the stocking environments, the stocking materials (farm and glass eels), the stages (smaller and larger eels) and times after stocking (Bisgaard and Pedersen, 1991;Pedersen, 1998;Lin et al, 2007;Simon et al, 2013;Simon and Do¨rner, 2014). In stocked (Pedersen, 2009;Simon et al, 2013) and non-stocked (Naismith and Knights, 1990;Lambert et al, 1994) eels, the recapture rates improved with increasing age and size.…”

Section: Introductionmentioning

confidence: 99%

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Short-term responses of glass eels transported from UK to small Belgian streams

Ovidio

Tarrago-Bes

Matondo

2015

Ann. Limnol. - Int. J. Lim.

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-Restocking of inland waters with glass eels is one of the recovery options to prevent the decline of European eel Anguilla anguilla (L.) populations. We studied the growth, dispersion, density and habitat preferences in the imported glass eels from UK and stocked in three typologically different small Belgian streams, using electrofishing surveys around the single release point, 1 year following stocking. Our results clearly support that the recaptured individuals stocked in our streams farther from the sea, survived, grew, dispersed upstream and downstream. Elvers exploited the complete transversal section of stream, with preference for the sheltered microhabitats near the banks with slower water velocity and low depth. Length-weight relationship was different between streams in terms of allometric coefficient (b). We assume that microhabitats and food availabilities lead to contrasted results in terms of growth and absolute occurrence. Restocking of glass eels in small middle-land streams was found to be an interesting and unconventional option that requires adequate stream and habitat selection.

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What happens to glass eels after restocking in upland rivers? A long‐term study on their dispersal and behavioural traits

Matondo

Séleck

Dierckx

et al. 2019

Aquatic Conservation

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1. The European eel Anguilla anguilla is a critically endangered fish species as a result of human activities and climate change in river and oceanic ecosystems. Restocking using glass eels in continental freshwater areas is a potential conservation measure for enhancing local eel stocks and for conserving the species in aquatic habitats, where it may otherwise disappear. However, little is known about the fate of these restocked individuals and the early ecological behaviour of the young eels translocated in rivers. 2.A portable radio-frequency identification (RFID) telemetry system and 12-mm tags were used to track restocked eels for a duration of 4 years. The aim was to understand the early movement, behavioural traits, dispersal, and habitat use of elvers after restocking performed in 2013 with glass eels in a shallow riverine environment.3. From the 241 tagged eels (total length, Q 50 = 152 mm), 85% were detected in 1968 positions during a period of 4 years, beginning in 2014. Clear seasonality in eel activity was observed, with higher mobility in summer when the water temperature was high (above 12°C). Dispersal was slowed by numerous artificial obstacles and the high carrying capacity of habitats. There was a negative relationship between the body size of eels at tagging and their mobility. Five behavioural categories of mobility patterns were identified: ascending, descending, oscillating with an upstream trend, oscillating with a downstream trend, and stationary. The first four categories depleted with time, in favour of stationary individuals that displayed a highly sedentary lifestyle.4. This study provides new knowledge of the long-term dispersal behaviour of restocked eels and the influence of seasons, barriers, and habitats on their colonization strategy changing with time. The results contribute to a better understanding of the issue of uncommon restocking practices in upland rivers.

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Comparison of growth and condition of European eels stocked as glass and farm sourced eels in lakes in the first 4 years after stocking

Cited by 33 publications

References 36 publications

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

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

Short-term responses of glass eels transported from UK to small Belgian streams

What happens to glass eels after restocking in upland rivers? A long‐term study on their dispersal and behavioural traits

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