Just go with the flow? Route selection and mortality during downstream migration of silver eels in relation to river discharge

Abstract

Jansen, H. M., Winter, H. V., Bruijs, M. C. M., and Polman, H. J. G. 2007. Just go with the flow? Route selection and mortality during downstream migration of silver eels in relation to river discharge. – ICES Journal of Marine Science, 64: 1437–1443. The European eel (Anguilla anguilla) has been in steep decline for several decades. Fisheries and hydropower-induced mortality presumably play an important role during the downstream migration of silver eels, and downstream-migrating silver eels must make various navigation and route-selection decisions to reach the sea. We examined the influence of river discharge on route selection of silver eels. To quantify the impact of hydropower and fisheries on silver eel mortality, radio-telemetry experiments were performed in the River Meuse in 2002 and 2004, surgically implanting 300 silver eels with Nedap-transponders. Route selection and passage behaviour near detection stations was assessed. Silver eels were distributed over the alternative migration routes in the river in proportion to the discharge until the silver eels reached the entrance to the turbines. The eels altered their behaviour when approaching the turbines of hydropower plants and showed stationary and recurrent behaviour. We discuss the consequences of this on route selection and mortality rates caused by hydropower facilities and fisheries.

Impact of Tide Gates on the Migration of Adult European Eels, Anguilla anguilla

“…Travade et al (2010) and others (e.g. Breteler et al 2007;Jansen et al 2007) suggest that eels tend to escape via the route of dominant flow, an observation supported by the current study in which most eels (75.9%) exited through Gate 1 which discharged the highest volume.…”

Silver eel downstream migration in fragmented rivers: use of a Bayesian model to track movements triggering and duration★

“…Many have focused on the behaviour of silver eels passing downstream through hydroelectric power stations to estimate mortality (Boubée and Williams, 2006;Carr and Whoriskey, 2008;Travade et al, 2010;Pedersen et al, 2012) or to improve mitigation solutions (Gosset et al, 2005;Russon and Kemp, 2011;Calles et al, 2013). Some studies have tracked silver eels along fragmented watercourses to estimate escapement (Haraldstad et al, 1985;Jansen et al, 2007;Acou et al, 2008;Breukelaar et al, 2009;Verbiest et al, 2012;Piper et al, 2013;Marohn et al, 2014;Mccarthy et al, 2014;Reckordt et al, 2014). Other studies have focused on migration triggered by environmental factors, to predict migration activity and especially peaks of migration, and consequently when to shutdown turbines (Vøllestad et al, 1986;Trancart et al, 2013).…”

Wetenschappelijke onderbouwing en ondersteuning van het visserijbeleid en het visstandbeheer: Onderzoeksprogramma visserij 2016 - eindrapport

“…Migratiepieken worden vooral waargenomen tijdens donkere nachten (bewolking, nieuwe maan) met veel neerslag, voornamelijk tussen zonsondergang en middernacht en de hoofdmoot trekt op minder dan 20 dagen tijd uit het stroomgebied weg waarbij voornamelijk de route met het hoogste debiet wordt gevolgd (Bertin 1951, Jansen et al 2007, Bruijs & Durif 2009). Zilverpalingen worden het meest gevangen in de hoofdstroom van de rivier (Tesch 2003) en schoolvorming wordt daarbij doorgaans niet waargenomen, ondanks de bijwijlen hoge lokale densiteit (Tsukamoto et al 2003).…”