Forsøksdyr: Monitoring of the wild European eel stock

Godkjenningsdato 28.04.2020

Godkjenningsperiode 01.07.2020-30.06.2022

The European eel population has been declining since the 1980's. It is a panmictic species and is managed as one stock although present in almost every European and some North African countries. Most countries are required (by the European Union or advised by ICES) to provide density and biomass estimates of their local stock as well as information on the age distribution and other biological characteristics. The goal of this study is to document the status of eels in Norway and understand their habitat usage in freshwater and marine habitats. This study will involve 1) a mark recapture program, 2) establishing biological profiles of eel living in saltwater versus freshwater 3) determining the age structure of eels in Norway 4) comparing the habitat use of eels between the freshwater and saltwater habitats by observing their seasonal and migratory movements using acoustic telemetry (acoustic array) and RFID technology (PIT tags and antennas).
The eels used in this study will be either tagged (2150), taken blood samples from (378) or sacrificed (927). Eels will be anesthetized before tagging/blood sampling and thus will feel miminum distress. The tags (acoustic tags or PIT tags) will be implanted in the body cavity and the procedure is well documented in the literature. Eels are known to recover well from the procedure and behave as normal eels do. The sacrificed eels will be euthanized by an overdose of anesthesia and therefore should not feel any distress.
The results are important for both national and international eel management and also in a wider scientific context to understand the life cycle of this species and what may influence their choice of habitat. Results will be published in international peer reviewed journals.
There is no possible replacement to achieve this study. We need the otoliths to study the life-history strategies of the eels. The telemetry survey constitutes a reduction of the number of animals in the experimental design since we will obtain continuous and detailed data of several inviduals rather than an instant "picture" of several individuals. All of the tagging and sampling will be carried out be experienced eel and telemetry scientists.
Samples will be taken along the whole Norwegian coast because we expect to find a latitudinal gradient in our results.
This study is part of a research financed and approved by the Norwegian Research Council (MAREEL, project number #280658) and by the Nordic Council of Ministers (project 2TEM: transcriptomic tool to determine European Eel marine residency for use in Monitoring and Management)