Simulated migration of European silver eel: effects of long term swimming and parasitic infection pressure on energy balance and gonadal development (LBI.4199)

The European eel (Anguilla anguilla L.) is an important species for aquaculture and fisheries. Recently a decrease was observed in the influx of glass eel. The question arises if this phenomenon can be ascribed to a reduced capacity of the spawners (silver eel) to reach the 6000 km from Europe located proposed spawning grounds in the Sargasso sea. Several possible causes can be given to explain the reduced influx of glass eel:

1. the silver eels have not enough energy supplies to reach the spawning grounds,
2. the animals become poisoned by the PCB levels which are released when fat is used,
3. the swimbladder of the animals is infected with the parasitic nematode Anguillicola crassus.

From a pilot experiment conducted in Leiden in a specially developed swim tunnel we demonstrated that eel can be induced to swim continuously (day and night) at a current velocity of 0.4 meter per second. The animal covered without signs of fatigue 4000 km. For migrating silver eel it is assumed that they perform the journey to the Sargasso sea without feeding. They migrate the distance of 6000 km during a period of 4-6 months, probably at a constant cruising speed. Furthermore it is generally believed a maturation of the gonads occurs during this migration period. However, never before an adult silver eel spawner has been observed in the Sargasso sea. Based only on the observation that the larvae (Leptocephali) of eel were observed in the Sargasso sea it is assumed that their spawning grounds are located in this area. To elucidate this paradox and to give an answer to the question whether starving silver eel can swim this distance, experiments have to be conducted in a large swim tunnel. Silver eel will be forced to swim 6000 km over a period of 4-6 months. This allows to analyze the physiological and endocrinological status, the release of PCB from the fat to the blood, the PCB pools in the blood and tissues and the development of the gonads. Furthermore the correlation between infection pressure with the swimbladder parasite Anguillicola crassus and the swimming performance will be examined. Results can directly be translated into policy making decisions such as maximally acceptable level of pollution of the inland waters with PCBS, and measures to limit infection of elvers with the swimbladderparasites in nature or on fishfarms. Furthermore if migration will result in gonad development and maturation under laboratory conditions this will be an important break-through in the knowledge of the reproduction physiology of eel.

Gebruikers

Er zijn één bedrijf en twee non-profit organisaties bij dit onderzoek betrokken.

Projectleider Dr. G.E.E.J.M. van den Thillart Universiteit Leiden Dierfysiologie Gorlaeus Laboratorium Postbus 9502 2300 RA LEIDEN email: thillart@chem.leidenuniv.nl

Status van het project Gestart : 01-05-1997 Einddatum : 01-03-2001 Trefwoorden vissen, aal, inspanningsfysiologie, energiemetabolisme, dierfysiologie, paling, ontwikkelingsbiologie, glasaal, palingtrek, visserij, aquacultuur, zilveraal, zwemblaasworm, viskwekerij .   Print | Over deze site |  Sitemap | Voorbehoud | Gewijzigd 7-3-2006 Nieuws uitgelicht Nieuwsbrief Technologiestichting STW, januari 2012 31 januari 2012 Elke maand stuurt Technologiestichting STW haar relaties een link naar de web-based nieuwsbrief. Hierin staat een maandelijks overzicht van het jongste nieuws van de bestuurstafel, onderzoeksnieuws, o... [meer]