Spawning biology, recruitment and genetic population structure of European eel (Anguilla anguilla) in the Sargasso Sea

Professor, PhD, dr. scient., Michael M. Hansen Afd. for ferskvandsfiskeri, Danmarks Fiskeriundersøgelser og dr. Scient Henrik Sparholt,  International Council for the Exploration of the Sea, ICES

Despite more than a century of research, much of the life history and spawning biology of European eel remains a mystery. At the same time, European and American eel face a catastrophic decline, and understanding of the factors involved is hampered by lack of knowledge of the biology of the species. Both species are assumed to spawn in the Sargasso Sea, yet the evidence is restricted to findings of newly hatched larvae. Spawning eels have never been caught, and the depth at which they spawn has been inferred indirectly. Moreover, previous assumptions about eel constituting one genetically homogenous population have been challenged by studies employing genetic markers. We propose that the Galathea 3 expedition operates in the Sargasso Sea 15 March to 7 April 2007. We intend to sample newly hatched larvae of both European eel and other eel species from different geographical locations. The abundance of larvae will be compared to data from previous cruises in order to estimate the decline of eels. Further, we will investigate the plankton ecosystem in which the eel larvae are spawned, focusing on the hydrographic influence on productivity and plankton distribution. Eel larvae, both European eel and other species, will be analysed using DNA markers in order to test if genetically different populations are present, and to identify if hybridisation between American and European eel is restricted to certain areas. We will release artificially matured eel implanted with tags that record depth and temperature and send the results via satellite. Finally, we will attempt to catch spawning eels using a large modern mid-water trawl. Eel spawning may be induced by new moon, and on 19 March 2007 (new moon) we will concentrate efforts at a particularly promising area.

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