Freshwater eels – on the agenda for protection and research

By |2018-08-31T16:30:05+00:00September 26th, 2016|Freshwater, IUCN, Species|0 Comments

A longstanding challenge within the world of species conservation is that a vast proportion of the money, time and research is focused on “charismatic” species. This is so pronounced, that even the giraffe, a classically unique and interesting species, has suffered from lack of attention – scientists have only recently discovered that there may in fact be four separate species of giraffe! With this in mind, it is easy to picture the plight of the freshwater eel – brown and slimy are tough characteristics to sell to the cute-loving masses. At Synchronicity Earth, one of our aims is to fill gaps in funding that have been otherwise overlooked, and our partnership with the IUCN Anguillid Eel Specialist Group has allowed us to support work on a family which is urgently in need of it.

European Eel: (Anguilla anguilla)

There are 16 known species of Anguillidae (freshwater eels) and three subspecies, and they are found all over the world in over 150 different countries. Freshwater eels have a complex and little understood developmental pattern, involving changes in physical morphology, migrations over huge distances, and the ability to live in completely different habitats. As an example, the European eel, while living most of its life in the rivers of Europe, migrates all the way across the Atlantic to the Sargasso Sea to spawn and lay eggs. Their larvae then follow oceanic currents to return to Europe, and grow into “glass eels” – transparent juvenile eels about eight cm long – which swim upstream to find suitable habitats in European rivers to live out their adult lives. When they reach maturity, many years and three development stages later, they make a final trip back out to sea for their only reproductive event before death. To make things even more complicated, not all eels follow this cycle, with many known to spend their whole lives in estuaries, lagoons or coastal waters without ever migrating to freshwater habitats. Moreover, it was found out that even individuals within the same species can display starkly different habitat use and migratory patterns. The combination of an intricate life history and a distinct lack of information on the members of the family, makes freshwater eels very difficult to protect.

For the few species of freshwater eel that are monitored, populations have displayed worrying declines over the past forty years or so. On top of this, we do not know enough about their ecology and threats to determine what is causing these declines. Their life cycle may mean that eels face different threats for each of the habitats they live in as well as for all of their varying life stages. For example, glass eels and sub-adults may be particularly vulnerable to dams and mining activities during their migration upriver, while adult eels could be threatened more by disease and parasites. Other overarching problems, such as climate change and pollution, threaten all the habitats the eels rely on, posing an extra threat. Exploitation for consumption is currently one of the biggest threats to freshwater eel species. Eels were historically an important foodfish in Europe, and continue to make up large parts of diets across East Asia, with fishing taking place both for direct consumption and to stock aquaculture farms. Although Japanese eels were originally the main supply to the East Asian market, they have suffered a massive population crash over recent decades, with catch numbers dropping from 140 tonnes in 1965 to below 40 tonnes in 2000. This has led to a worrying reliance on imports of Critically Endangered European eels to stock farms in Asia. In 2010, the European Union banned all trade of eels in and out of its borders in an attempt to protect the species. However, the black market trade is still rife, with European eels fetching a whopping $1,000 per kilo in East Asian markets.

The IUCN Anguillid Eel Specialist Group is doing fantastic work to support freshwater eels worldwide. They originally focused on addressing the serious lack of information on freshwater eels, as without solid knowledge of their life cycles and habitats, it is even harder to protect them. A workshop (the first of its kind) was held in 2013 in order to gather together all the information available for 13 eel species, and assess them according to the IUCN Red List categories and criteria. This resulted in these assessments being published online by the IUCN, which is a vital step for any species if it is to be monitored and protected. Of the 13 assessed species, four are Vulnerable to extinction, Endangered, or Critically Endangered, and three were classified as Data Deficient. This means that more research and monitoring in the field is needed to fully understand the threat to freshwater eels.

The classification of multiple eel species as endangered has allowed the Anguillid Eel Specialist Group to promote various forms of protection for the most threatened species. In August 2014, a workshop was held in Japan to promote the conservation of the Japanese eel and to place some controls on eel farming. Later that year, the group succeeded in having the European eel listed on Appendix II of the Convention on Migratory Species, which puts pressure on all range states to focus on the conservation of the species.

More recently, the specialist group spearheaded a proposal at the IUCN World Conservation Congress for a motion which promotes Anguillid eels as a flagship species for aquatic conservation. They argued that the main threats to eels are also threats to thousands of other species in both marine and freshwater environments. They also pointed out that by protecting a highly migratory species, conservationists would be meeting a range of other goals related to connecting habitats and ecological networks. This motion was adopted, which is excellent news for our slippery friends, as it means that future work from the IUCN and its partners is more likely to focus on freshwater eels.

If there is anything we can learn from freshwater eels, it’s that a pretty face isn’t everything. Hopefully in the coming years our partners at the Anguillid Eel Specialist Group will be able to learn much more about freshwater eels and their fascinating life cycles, as well as develop better systems for protecting them and their habitats.

Share This Story

Go to Top