Estuarine-Specific Migration of Glass Eels in the Ems Estuary

Huisman, Jeroen; Kuipers, H.; Nagelkerke, L.A.J.; Schollema, Peter Paul; Knaap, Inge van der

doi:10.3390/fishes8080392

Cited by 1 publication

(1 citation statement)

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“…In the NSC, glass eels showed an average migration speed of 0.7 km/day and increasing speeds with increasing temperatures, with peaks of 1.8 km/day. Glass eels at other sites showed migration speeds of 3–4 km/day in the Gironde basin and 3–5 km/day in the Sevre Niortaise River [ 25 ], > 2 km/day in the Ems estuary [ 56 ] and 1.6–8.4 km/day for A. rostrata in the Penobscot River [ 26 ]. In the Cabot Strait, migration speeds were as high as 10–15 km/day [ 57 ].…”

Section: Discussionmentioning

confidence: 99%

Glass eel migration in an urbanized catchment: an integral bottleneck assessment using mark-recapture

Griffioen,

Wilkes,

van Keeken

et al. 2024

Mov Ecol

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Diadromous fish such as the European eel (Anguilla anguilla L.) are hampered by a high density of barriers in estuaries and freshwater systems. Modified and fragmented waterbodies lack tidal flows, and habitat may be less accessible and underutilized compared to free-flowing rivers and estuaries. With rising sea levels and increased occurrence of droughts, the number of barriers may further increase, implying that the need to study migration in such areas may even become more urgent worldwide. To study glass eel migration and behaviour in such highly modified water systems, a mark-recapture study was carried out in the North Sea Canal (NSC) basin, which drains into the North Sea via a large sluice complex. In total, eight uniquely tagged groups (3,797 glass eels) were released near the sluice complex, and 11 groups (2,663 glass eels) were released at inland barriers upstream over a 28 km long stretch in the NSC in spring 2018. The sluice complex attracted 10.3 million glass eel and did not block or delay their immigration. The large and diurnally intensively used coastal ship locks and allowings some saltwater intrusion, efficiently facilitated glass eel migration. Once in the NSC, water outlets from adjacent polders attracted glass eels relative proportional to the discharge of pumping stations. In the NSC, average migration speeds of 0.7 km/day (max. 1.8 km/day) were measured, and this increased with higher temperatures. Redistribution of glass eel from accumulations at inland barriers to other outlet locations was observed in both upstream and downstream directions in the NSC. Passage success and residence time (‘delays’ of 4.1–13.7 days) varied between the different inland barriers. Most of the glass eel, however, appears to settle in the easily accessible habitats within the brackish NSC catchment. This study combined an integral assessment of successive bottlenecks in a modified inland water system.

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