Surveying eels in the North Kent Marshes
ZSL, together with the Environment Agency, have been setting nets throughout the ditches in the North Kent Marshes to investigate eel populations. The presence and density of eels in these unique environments will give us a better understanding of eel habitat preferences in the region and help conservation and management efforts for this distinctive and endangered species.
Recruitment of the European eel (Anguilla anguilla) has experienced up to a 90% decline in the past three decades on a continent wide scale (ICES, 2002). This has led to EU legislation and many conservation projects to protect and conserve the unique species. Eels are culturally and economically important across Europe, being fished for traditional cuisine, such as the jellied eel served with mash throughout east London.
Eels have a complex and dynamic life cycle, spawning in the Sargasso Sea and migrating to Europe on ocean currents. They enter the European continental shelf as sexually undifferentiated glass eels where they migrate on the tide towards freshwater, maturing into elvers. As they feed and grow, these then mature into yellow eels and eventually silver eels. Once the processing of silvering has occurred the eels migrate back to the Sargasso Sea. Threats to eel populations during their continental phase include barriers preventing migration, habitat destruction, over fishing, and pollution.
The coastal and estuarine waters of the Thames are believed to be especially productive for eels and the North Kent marshes provide important brackish water eel habitats. The marshes are already recognised for their significance for many bird species and are protected in some areas. No previous eel specific surveys have been conducted through the area so little is known about the resident populations.
Fyke netting (a specific design of net that can be used for catching eels) has been carried out across four sites in the North Kent marshes to assess the presence and abundance of yellow and silver eels. The sites vary in habitat structure and management schemes, allowing an assessment of factors affecting eel abundance.
The project focuses on the threats to eels at a site specific level including water quality, food availability, fishing pressure, management and structural alteration of the sites. The results will allow an assessment of whether or not the North Kent Marshes are critical habitat for eels, and if they are in need of greater protection. It will also identify management and conservation strategies for greater protection of eels in the South-East of England.
An understanding of population dynamics throughout this unique habitat will allow better management of eel specific areas, and allow conservation projects to be directed in appropriate ways. The conservation of eels and the habitats that are important during their development will allow individuals to return to the Sargasso Sea to breed.