Habitat selection of the European eel
The European eel is said to be a catadromous migratory fish, which ascends into rivers to grow after it has completed its larval migration across the Atlantic Ocean to the European coasts. Nowadays, this simple behavioral pattern is more and more questioned. The migratory behavior of eels during the continental life phase has not been investigated yet and nothing is known about its influence on eel growth and health.
The project „Habitat selection of the European eel“ aimed at reconstructing the migratory behavior and habitat preference of European eels in order to gain insights into the largely unknown life of this fish species and to assess the influence of abiotic factors on health and spawner quality. The individual life history of eels was investigated by microchemical analyses of the element composition of their otoliths. This should provide insights into their migratory behavior and into the relationship between behavior and different fitness parameters.
By using LA-ICP-mass spectrometry and electron microprobe analysis we investigated the trace element composition of eel otoliths from different habitats. On the basis of the incorporation of specific elements we reconstructed movements between waters of different salinities. Spawner quality was assessed on the basis of fat content analysis and comprehensive parasite and virus analyses. These spawner quality criteria were correlated with different migratory patterns.
The analysis of element profiles of 321 eels from different waters revealed a high complexity of the migratory behavior of European eels. They have individual migratory patterns and occasionally also migrate repeatedly between salt and fresh waters, long before they start their migration back to their spawning ground in the Sargasso Sea.
The parasite load of eels was used as an important indicator for their health status. Out of the 35 detected parasite species, the swim bladder nematode Anguillicola crassus and the gill parasites of the genus Pseudodactylogyrus must be considered to be potentially harmful due to their high infection intensities.
With regard to eel specific virus infections we only detect single cases of Herpesvirus anguillae (HVA) and Eel Virus European-X (EVEX) in Northern German waters.
In addition, our analyses revealed that eels that live in coastal waters throughout their continental life phase have a higher spawner quality compared to individuals that exclusively lived in freshwaters. This finding is of great importance with regard to the current stocking practice, where almost exclusively freshwaters are used for stocking measures.
Project report: download.ble.de/04HS065.pdf
10.2005 - 2.2009
Project funding number: 04HS065
Project status: finished