STEEL – Improving knowledge of the effects of glass eel stocking
KEY POINTS- Compare locally recruited and imported eels in laboratory and field studies
- Analyse more than 40 years of monitoring data on glass eel stocking
- Produce an open-access knowledge database on the effects of glass eel stocking
Project overview
Participants
More related research
Short summary
The European eel is critically endangered, yet it remains unclear whether stocking with juvenile eels actually strengthens the population. In this four-year research project, we will investigate the effects of eel stocking and provide a stronger scientific basis for future eel management.
The European eel has declined by 92–99% and is classified as critically endangered. A common management measure to counteract this decline is the stocking of young eels, known as glass eels. Eels play an important ecological, cultural and economic role, and since the EU Eel Regulation came into force in 2007, stocking has been a central component of the management plans of many countries.
Unlike many other species that are stocked, such as salmonids, eels cannot currently be produced in captivity. Instead, stocking relies on capturing wild glass eels in areas with high recruitment, holding them in quarantine, and then transferring them to areas with lower recruitment. This process may affect their behaviour, physiology and interactions with naturally recruited eels in ways that are not yet fully understood.
In Sweden, around 90% of the eel currently found in inland waters originates from stocking. However, it remains unknown whether stocking provides a genuine net contribution to the shared European eel population, or whether stocked eels instead compete with locally recruited eels. Despite the fact that the ecological effects of eel stocking remain largely unknown, the measure enjoys broad support among both policymakers and stakeholder organisations.
In this four-year project, we will evaluate the effects of stocking as a management measure by:
- Identifying behavioural and physiological differences between locally recruited and imported, quarantined glass eels in controlled laboratory experiments.
- Comparing migratory behaviour and mortality between locally recruited and stocked eels in field studies using PIT tagging.
- Investigating the effects of stocking on mortality, growth and production in Swedish lakes and coastal waters by analysing more than 40 years of environmental monitoring data and otolith chemistry.
- Developing a systematic evidence review and open-access database on the effects of stocking in European and Japanese eel, providing a resource for future research and management.
The results of STEEL are expected to be highly relevant to eel management at both national and international levels and to contribute to better-informed, sustainable decisions on how eel populations can best be conserved.
Participants
Josefin Sundin (project manager, associate professor SLU Aqua)
Philip Jacobson (researcher SLU Aqua)
Fredrik Jutfelt (professor University of Gothenborg)
Anders Nilsson (professor Lund University)
PhD student (to be recruited)