Eel

Interesting Facts

Japanese eels, Anguilla japonica, can surmount natural waterfalls up to 46 m high.

Matsushige, Kazuki, Yusuke Hibino, Yoshiya Yasutake, and Noritaka Mochioka. “Japanese Eels, Anguilla Japonica, Can Surmount a 46-M-High Natural Waterfall of the Amikake River System of Kyushu Island, Japan.” Ichthyological Research 68, no. 1 (2021): 21–31. https://doi.org/10/g62g23.

In Switzerland, specimens have been recorded at altitudes of 3,000 feet (925 m) above sea level.

Schmidt, Johs. “The Breeding Places of the Eel.” Philosophical Transactions of the Royal Society of London. Series B, Containing Papers of a Biological Character 211, no. 382–390 (1923): 179–208. https://doi.org/10/dc9gpq.

Given their catadromous life cycle and their global commercial and cultural importance, anguillid eels can serve as indicator, umbrella, and flagship species, as well as a broader surrogate for freshwater biodiversity conservation.

Itakura, Hikaru, Ryoshiro Wakiya, Matthew Gollock, and Kenzo Kaifu. “Anguillid Eels as a Surrogate Species for Conservation of Freshwater Biodiversity in Japan.” Scientific Reports 10, no. 1 (2020): 8790. https://doi.org/10/jknd.

Regarding Anguilla megastoma (Polynesian eel), an IUCN Red List note reports that many occur at higher altitudes. The note also cites evidence that this species can cross obstacles by leaving the water and crawling over moist ground. Individuals sampled in Lake Letas, 7 km inland on Gaua Island, Vanuatu, likely passed Siri Falls (120 m high) as elvers.

In Australia, elvers move around the 140 metre Warragamba Dam to reach Lake Burragorang. Scientists track amazing eel migration

Baba-Yaga, the witch in Slavic folklore, has a name linked to the same root as the early Latin "anguis" (snake). This root also relates to anguilla, the genus name, and to many words in European languages.1

European eels (Anguilla anguilla) grow in European rivers and lakes, then migrate roughly 5,000 to 7,000 km to the Sargasso Sea in the western Atlantic to spawn. This is one of the longest known fish migrations. Spawning occurs across a vast region of the Sargasso Sea, about 2,000 km wide.2 No one has observed the exact spawning sites directly.

European eels are four to six times more efficient at long-distance swimming than salmonids, with an energetic cost of 10 to 12 mg fat per km.3

The long spawning migrations of catadromous anguillid eels from freshwater to the open ocean appear to be a relic of reproductive behaviour shared with deep-ocean pelagic eels.4 The likely basal species (A. borneensis) and tropical eels have much shorter migrations.5

There are legends of eels living 155 years (the Brantevik Eel in Sweden, in a well). There are also reports of New Zealand longfin eels living for more than 100 years. In Sweden, people reportedly kept eels in wells to help clean the water by preying on small animals and insects.

List of Species

A. oelebesensis
A. interioris
A. megastoma
A. anoestralis
A. nebulosa nebulosa
A. nebulosa labiata
A. marmorata
A. reinhardtii
A. borneensis
A. japonica
A. rostrata
A. anguilla
A. dieffenbachii
A. mossambica
A. bicolor pacifica
A. bioolor bioolor
A. obsoura
A. australis australis
A. australis sohmidtii

Aoyama, Jun. ‘Origin and Evolution of the Freshwater Eels, Genus Anguilla’. In Eel Biology, edited by Katsumi Aida, Katsumi Tsukamoto, and Katsumi Yamauchi. Tokyo: Springer, 2003.

Known or suspected spawning sites for well-studied Anguilla spp.: 1, A. anguilla; 2, A. australis; 3, A. bengalensis; 4, A. celebesensis; 5, A. dieffenbachii; 6, A. japonica; 7, A. marmorata; 8, A. mossambica; 9, A. reinhardtii; 10, A. rostrata. The coasts of regions colonized by them are shaded grey. Warm currents that are likely to carry larval Anguilla spp. from spawning areas to the growth habitat are shown by arrows.

Watanabe, Shun. ‘Taxonomy of the Freshwater Eels, Genus Anguilla Schrank, 1798’. In Eel Biology, edited by Katsumi Aida, Katsumi Tsukamoto, and Katsumi Yamauchi, 3–18. Tokyo: Springer, 2003.

Righton, David, Kim Aarestrup, Don Jellyman, Phillipe Sébert, Guido van den Thillart, and Katsumi Tsukamoto. ‘The Anguilla Spp. Migration Problem: 40 Million Years of Evolution and Two Millennia of Speculation’. Journal of Fish Biology 81, no. 2 (2012): 365–86. https://doi.org/10/f35nf8.

Righton, David, Kim Aarestrup, Don Jellyman, Phillipe Sébert, Guido Van Den Thillart, and Katsumi Tsukamoto. ‘Extreme Swimming: The Oceanic Migrations of Anguillids’. In Swimming Physiology of Fish, edited by Arjan P. Palstra and Josep V. Planas, 19–44. Berlin: Springer, 2013.

The traditional eel fishery at Lake Condah and its historical and cultural significance to the Gunditjmara people.

Rose, Denis, Damein Bell, and David A. Crook. “Restoring Habitat and Cultural Practice in Australia’s Oldest and Largest Traditional Aquaculture System.” Reviews in Fish Biology and Fisheries 26, no. 3 (September 1, 2016): 589–600. https://doi.org/10/gf7spf.

Issues

non-cuddly species
moral status (sentience, pain)
hard-to-study systems (ocean as a hard-to-access environment, large size)
distributed systems (connectivity and reproductive migrations)
forms of life in need of drastic reframing (from food to kin)
long-duration systems
loss of cultures (e.g., eels on the river Thames have lost the culture for going upstream) 6
need to monitor all stages of complex life histories (but there are successful citizen science examples)7

Food

Kemmerer, Lisa. “Ethics and Eating Fishes.” Journal of International Wildlife Law & Policy 19, no. 3 (2016): 203–18. https://doi.org/10/g3xnkt.

Kemmerer, Lisa. “If You Care About Anymals, Do Not Fish (or Eat Fishes) *.” In New Omnivorism and Strict Veganism, edited by Cheryl Abbate and Christopher Bobier, 179–97. New York: Routledge, 2023.

Evolution

Evolution of the eel – a matter of continental drift

Ecology, Relationships, Processes, Niche Construction and Lifeworlds

Coevolution and Mutualisms

Interpret as give and take in diverse worlds, moving beyond mechanistic explanations to consider eel relations as forms of politics, economy, culture and expertise, at least as seriously taken provocations. Comparative infection experiments involving Japanese and European eels showed differences in immune defence, reflecting coevolution versus an abrupt host switch. This is interesting as an example of rapture.

In the Baltic, eels formed close association with eelgrass habitats (seagrass meadows).8

Parasite Coevolution

Evidence suggests coevolution between the nematode genus Anguillicola and four Indo-Pacific eel species that act as hosts.9 This is an interesting example of how anthropogenic relocation can create a rupture and a "sacrifice zone" or "dissonance field".10

Niche Segregation/Partitioning

Differences in migratory and movement patterns between the two freshwater and marine eel species lead to niche segregation in the brackish bay where they coexist. It is possible that the catadromous behaviour of anguillid eels may have evolved as an adaptation to avoid competition with marine eels such that the interspecific competition drove their life history shift into freshwater habitats.11 This is an example of compromise and negotiations between nonhuman beings.

Similarly, species A. marmorata utilizes clear, fast-flowing mainstems and tributaries with larger substrates, while the temperate species A. japonica prefers stagnant, muddy estuaries, backwater areas, and reservoirs. Such niche partitioning allows the two species to coexist by reducing competition due to their similar niches, suggesting an interspecies relationship mediated by resource use.12 A similar partitioning occurs in Taiwan.13

Movement Ecology

Station keeping takes place within the home range of the animal and corresponds to simple movements for foraging and predation avoidance.

Ranging and migration occur outside the home range.

Ranging: the search for a resource (mate, food, etc.). Stops when the resource is found.

Migration: triggered by physiological and environmental cues, not by the search for a resource. It affects most individuals in the population, occurs over a long timescale, requires orientation, and suggests a return journey.

Diadromous fish, such as eels, undergo two long migrations.

From the spawning grounds to growth habitat, includes active upstream migration in river catchments during the early years of their continental life stage.

During the second migration eels return to the oceanic spawning grounds from their growth habitats in rivers or coastal waters.

Eels may also move between different habitats during their continental stage, movements which correspond to station keeping and ranging.

Drouineau, Hilaire, Caroline Durif, Martin Castonguay, Maria Mateo, Eric Rochard, Guy Verreault, Kazuki Yokouchi, and Patrick Lambert. “Freshwater Eels: A Symbol of the Effects of Global Change.” Fish and Fisheries 19, no. 5 (2018): 903–30. https://doi.org/10/gns2r3.

Sentience and Cognition

There is quite a bit of research on the Japanese eel behaviour by Watanabe, e.g.:

Watanabe, Shigeru. “Spatial Learning in Japanese Eels Using Extra- and Intra-Maze Cues.” Frontiers in Psychology 11 (2020): 01350. https://doi.org/10/g5twt7.

Geographies

European

Confirms the importance of the Mediterranean rivers.

Amilhat, Elsa, Kim Aarestrup, Elisabeth Faliex, Gaël Simon, Håkan Westerberg, and David Righton. ‘First Evidence of European Eels Exiting the Mediterranean Sea During Their Spawning Migration’. Scientific Reports 6, no. 1 (2016): 21817. https://doi.org/10/f9k7gm.

Australian

Koster, Wayne M., Kim Aarestrup, Kim Birnie-Gauvin, Ben Church, David Dawson, Jarod Lyon, Justin O’Connor, et al. ‘First Tracking of the Oceanic Spawning Migrations of Australasian Short-Finned Eels (Anguilla australis)’. Scientific Reports 11, no. 1 (2021): 22976. https://doi.org/10/gn77qh.

Is this Australia's most hardcore animal?

Eels can travel over land, climb walls, and take down substantial prey. They are catadromous, meaning they live in freshwater but migrate to the ocean to breed. Two common eel species in Australia are the short-finned eel (Anguilla australis) and the long-finned eel (Anguilla reinhardtii). Both species spawn in the Coral Sea, near the Great Barrier Reef, after swimming thousands of kilometres from the east coast of Australia and New Zealand. This is one of the longest known migrations in Australian waters, but the exact location of their breeding grounds remains uncertain. Scientists are tracking eels with satellite tags to better understand this migration. Eels can live for decades in freshwater or estuaries before returning to the ocean to breed once and die. They are an important food source for many animals, including sharks and whales, as well as humans. Eels are also culturally significant for some Indigenous groups, who have harvested them for thousands of years.

Fishing

In Victoria, there is fishing for eels and a 2017 management plan.

Eels of Elizabeth Street in Melbourne

(Jefa Greenaway, Judith Alcorn, Mark Gillingham, landscape architect)

Wurundjeri elder Dave Wandin reckons eels moving through Melbourne drains is an urban legend, but he’s not about to rule it out completely.

One eel of a story: the slippery truth of a fishy underground migration (The Age)

American

Tracking American eels on the open sea to crack the mystery of their migration

The Secret Life of Eels

Ecosystem Engineering, Niche Construction, and Habitat Modification

The American Eel plays an important role in the structure of tropical lotic food webs through top-down effects that are potentially augmented by in-stream barriers, linking the eel's role to habitat features.14

The migration of Anguillid Eels facilitates connections and relationships throughout water systems, facilitating the movement of nutrients and energy within ecosystems.15^,16^,17^,18

American eels construct burrows by forcing their heads and bodies into the substrate with rapid undulations, a form of bioturbation that changes physical habitat. They can form craters or mounds around burrow openings, physically altering the sediment surface. Eel burrows observed in both laboratory and field settings can have up to five openings, creating complex, multi-holed structures.19

Japanese eels selectively feed on infaunal organisms, possibly by digging burrowing prey into the water column, a behaviour that may change sediment and affect the benthic community. They can construct burrows up to 30 cm deep, covering the usual depths of many macrobenthic invertebrates and implying substantial physical interaction with estuarine substrate.20 European eel (Anguilla anguilla) is one of the three species with the highest maximum potential bioturbation (silt perturbation) impact score, indicating a significant role in sediment reworking.21

Eels engage in ecosystem engineering through continuous activity in soil, which enhances soil porosity and reduces bulk density, similar to the effects of earthworms. The eel co-culture system can shift ammonia-oxidizing microbial communities by altering soil physicochemical properties, which can in turn promote nitrification.22 This can be useful in rice cultivation,23 suggesting a service relationship with humans.

Eels are the only fish members of the nocturnal stream community (also including crayfish, amphibians, and macroinvertebrates) that are likely driving diel patterns of seston transport.24

Eels select particular substrates. European eel elvers prefer coarse gravel, suggesting that conservation efforts may benefit from targeting this type of substratum in marine coastal areas.25 Anguillid eels use mud as a substrate refuge only in the absence of substrate cavities, and that the winter distribution of eels in coastal bay and estuarine habitat is limited to waters warmer than the freezing point of fish tissue (~–0.7°C).26

The European eel can host most of the widespread European unionid mussel species, suggesting a role in the dispersal and survival of these ecosystem-engineering taxa. Freshwater bivalves, including unionids, are important ecosystem engineers because they contribute to filtration, nutrient cycling, bioturbation, and habitat provision for other benthic organisms.27

Multiple direct and indirect effects in structuring food webs.28

Human Impact

Drouineau, Hilaire, Caroline Durif, Martin Castonguay, Maria Mateo, Eric Rochard, Guy Verreault, Kazuki Yokouchi, and Patrick Lambert. ‘Freshwater Eels: A Symbol of the Effects of Global Change’. Fish and Fisheries 19, no. 5 (2018): 903–30. https://doi.org/10/gns2r3.

Rose, Denis, Damein Bell, and David A. Crook. ‘Restoring Habitat and Cultural Practice in Australia’s Oldest and Largest Traditional Aquaculture System’. Reviews in Fish Biology and Fisheries 26, no. 3 (1 September 2016): 589–600. https://doi.org/10/gf7spf.

Turbines

Buysse, David, Ans M. Mouton, Maarten Stevens, Tom Van den Neucker, and Johan Coeck. ‘Mortality of European Eel After Downstream Migration Through Two Types of Pumping Stations’. Fisheries Management and Ecology 21, no. 1 (2014): 13–21. https://doi.org/10/gswm6h.

Human-Eel Relationships

Rice-eel co-culture.

Eel reintroduction to control invasive fish.

Consider “zones of sympatry” where humans and eels have coexisted for a long time, e.g., since the Pleistocene.

Harris, Cornelia B., Alandeom W. Oliveira, Brett L. M. Levy, Alan R. Berkowitz, and Chris Bowser. ‘The Eel Connection: Developing Urban Adolescents’ Sense of Place Through Outdoor Interactions with a Local Organism’. The Journal of Environmental Education 54, no. 4 (2023): 241–64. https://doi.org/10/gswmzr.

Jensen, Casper Bruun. ‘The Anthropocene Eel: Emergent Knowledge, Ontological Politics and New Propositions for an Age of Extinctions’. Anthropocenes – Human, Inhuman, Posthuman 1, no. 1 (2020): 1–11. https://doi.org/10/gswkph.

Boswell, Anna. “The Sensible Order of the Eel.” Settler Colonial Studies 5, no. 4 (2015): 363–74. https://doi.org/10/g4jpm5.

As Food

Long View

Long relationships between eels and humans, including multiple species of Homo, provide a rare lens into landscape use, landscape modification, population migration, and place practices. This relates not only to food, but also to wider human-nonhuman interactions and place change.

Human-environment feedback systems with important biodiversity consequences are likely a recurrent feature of the Late Pleistocene, perhaps with even deeper roots. Of course, nonhuman living beings modify niches too.29

Around 92,000 years ago in Malawi, human activities (for example, modified fire regimes) relaxed seasonal constraints on ignition, influencing vegetation composition and erosion. In tandem with climate-driven changes in precipitation, this contributed to an ecological transition toward an early, pre-agricultural anthropogenic landscape.30

Other species of Homo lived in Andalusia, Spain, and fished for and ate eels (along with many other fish species) from about 500,000 to 45,000 years ago.31^,32^,33

Middle Pleistocene hominins, including Homo heidelbergensis and Homo neanderthalensis, had nutritional requirements comparable to Homo sapiens and benefited from the availability of eels as food in river valleys and floodplains. Eels (Anguilla) were available throughout the year in floodplain landscapes and provided a high-fat, high-carbohydrate food source that helped hominins maintain their protein-to-calorie balance.34

Human modification of the landscape, specifically in relation to eel aquaculture and management, began around the Pleistocene-Holocene transition, with more obvious indications appearing about 4000 years ago in Victoria, Australia.35

Details of significant environmental changes on Mangaia, Cook Islands, initiated by Polynesian colonization around 2500 to 1800 years ago, including major forest clearance, increased erosion, and species extinctions, demonstrate substantial human modification of the landscape. Prehistoric Mangaians heavily exploited freshwater eels (Anguilla sp.), suggesting resource exploitation that coincided with environmental change.

European eels were harvested by Mesolithic and Neolithic peoples in the western Baltic over millennia, but the major decline of 98% in the eel population has occurred since 1980. There is a long-term connection between pre-modern humans, anguillid eels, and eelgrass habitats (seagrass meadows).8

Now and into the Future

Prohibitions on the use as food:

Leach, B. Foss, Janet M. Davidson, and Fiona J. Teal. “Freshwater and Marine Eels in the Pacific and New Zealand: Food Avoidance Behaviour and Prohibitions.” Archaeofauna 31 (2022): 11–56. https://doi.org/10/g62jv9.

Japan

In 2012: "The Japanese nation has a long history of using freshwater eels as food, and these days up to ~100,000 t of eels per year are consumed there, about 70 % of the world’s eel consumption."

Kuroki, Mari, Martien J. P. van Oijen, and Katsumi Tsukamoto. “Eels and the Japanese: An Inseparable, Long-Standing Relationship.” In Eels and Humans, edited by Katsumi Tsukamoto and Mari Kuroki, 91–108. Tokyo: Springer, 2014.

Matsushige, Kazuki, and Yusuke Hibino. “Exploring Recent Japanese Public Perception of Freshwater Eels of the Genus Anguilla Using Content Analysis of Newspaper Coverage.” Aquatic Conservation: Marine and Freshwater Ecosystems 35, no. 7 (2025): e70164. https://doi.org/10/g9s22g.

Hamidoghli, Ali, Jinho Bae, Seonghun Won, Seunghan Lee, Dae-Jung Kim, and Sungchul C. Bai. “A Review on Japanese Eel (Anguilla japonica) Aquaculture, with Special Emphasis on Nutrition.” Reviews in Fisheries Science & Aquaculture 27, no. 2 (2019): 226–41. https://doi.org/10/g9s24h.

Fishing, Aquaculture, and Trade

Alonso, Aitor Ibáñez, and Daan P. van Uhm. “The Illegal Trade in European Eels: Outsourcing, Funding, and Complex Symbiotic-Antithetical Relationships.” Trends in Organized Crime 26, no. 3 (2023): 293–307. https://doi.org/10/gt76v8.

Yuan, Yuan, Yongming Yuan, Yunyun Dai, Yunchong Gong, and Yiqun Yuan. “Development Status and Trends in the Eel Farming Industry in Asia.” North American Journal of Aquaculture 84, no. 1 (2022): 3–17. https://doi.org/10/gjkbmp.

Shiraishi, Hiromi, Yu-San Han, and Kenzo Kaifu. “Eel Consumption in Japan: Insights from Genetic Species Identification and Trade Data.” Fisheries Science, 2025. https://doi.org/10/g9s27z.

Design and Conservation Initiatives

Measures:

remove barriers to migration, fish pass design, guidance on pass design (UK), advice on passes and other measures (UK), commercial services, eel tiles
raise public awareness about the importance of safeguarding eel habitats

Organisations:

Welfare, Sentience, Stress, and Pain

Cf. Aquaculture, Welfare, and Ethics

There is literature on neck cutting and electrocution of eels during slaughter.

Welfare implications of live chilling and freezing of farmed eels including the time to reach unconsciousness, based on ECGs and pain responses.

Lambooij, Elbert, Jan Willem van de Vis, Robert Jan Kloosterboer, and Cornelis Pieterse. “Welfare Aspects of Live Chilling and Freezing of Farmed Eel (Anguilla anguilla L.): Neurological and Behavioural Assessment.” Aquaculture 210, no. 1 (2002): 159–69. https://doi.org/10/b2p6gb.

Farmed and wild-caught eels may be exposed to many stressful and painful experiences, including injuries and mortalities.

Vettese, Troy, Becca Franks, and Jennifer Jacquet. “The Great Fish Pain Debate.” Issues in Science and Technology 36, no. 4 (2020): 49–53.

Trafficking

Pons-Hernandez, Monica. “‘Missing the Trees for the Forest?’ An Analysis of the Harms to European Eels Caused by Their Trafficking and Trade.” Critical Criminology 32, no. 1 (2024): 77–95. https://doi.org/10/gt9fjn.

Pons-Hernandez, Monica. “Inside the Slippery World of Glass Eel Trafficking: Lessons Learned from Spain to Prevent the Illegal Trade of European Eels.” European Journal of Criminology, 2024, 14773708241262885. https://doi.org/10/gt9fjq.

Research Approaches

Humanities

Some references on ethnographic and similar approaches to hidden and watery creatures.

Alaimo, Stacy. “The Anthropocene at Sea: Temporality, Paradox, Compression.” In The Routledge Companion to the Environmental Humanities, edited by Ursula K. Heise, Jon Christensen, and Michelle Niemann, 153–61. London: Routledge, 2017.

Bastian, Michelle. “Whale Falls, Suspended Ground, and Extinctions Never Known.” Environmental Humanities 12, no. 2 (2020): 454–74. https://doi.org/10/gmwpvq.

Hale, Sadie E. “On Sharks Unseen: Oceanic Non-Encounters and Multispecies Ethnography.” Swamphen: A Journal of Cultural Ecology (ASLEC-ANZ) 10 (2024). https://doi.org/10/gt73sk.

Mueller, Martin Lee. Being Salmon, Being Human: Encountering the Wild in Us and Us in the Wild. White River Junction: Chelsea Green Publishing, 2017.

Swanson, Heather Anne. “Methods for Multispecies Anthropology: Thinking with Salmon Otoliths and Scales.” In Multiple Nature-Cultures, Diverse Anthropologies, edited by Casper Bruun Jensen and Atsuro Morita, 81–99. Berghahn Books, 2019.

Sciences

genetic analysis
eDNA
satellite tags
acoustic tags
stable isotope analysis
comparative morphology
behavioural observation
stomach content analysis

Mapes, Murray, and Emma Mouillot. “Taxonomic Challenges and Advances in Eel Family Classification: Integrating Multidisciplinary Approaches.” FishTaxa - Journal of Fish Taxonomy 29 (2023): 24–35.

See Data Acquisition

Historical Ecology

Important as a way to establish trends that can demonstrate flexibility and projections into the future.

Questions:

How have eels populated new habitats? (tens of millions of years; longer and longer migrations from the ocean to freshwater)
What are the dynamics of eels encountering hominid and early human predation and harvesting? (tens of thousands of years; modified landscapes and population dynamics)
What are the political, economic, and cultural consequences of eel harvesting and trade? (thousands of years; trade, competition, switching to eels after other fishes were overfished, etc.)

Lajus, Dmitry, Jekaterina Glazkova, Dmitry Sendek, Vadim Khaitov, and Julia Lajus. “Dynamics of Fish Catches in the Eastern Gulf of Finland (Baltic Sea) and Downstream of the Neva River during the 20th Century.” Aquatic Sciences 77, no. 3 (2015): 411–25. https://doi.org/10.1007/s00027-014-0389-9.

Lajus, Julia, Alexei Kraikovski, and Dmitry Lajus. “Coastal Fisheries in the Eastern Baltic Sea (Gulf of Finland) and Its Basin from the 15 to the Early 20th Centuries.” PLOS One 8, no. 10 (2013): e77059. https://doi.org/10.1371/journal.pone.0077059.

Yurtseva, Anastasia, Elena Salmina, Alfred Galik, and Dmitry Lajus. “How a Millennium of Fishing Changed Fish Populations: A Case Study of Lake Peipus and the Velikaya River (NW Russia).” Aquatic Sciences 77, no. 3 (2015): 325–36. https://doi.org/10.1007/s00027-014-0381-4.

Japanese Eel Demographics

This study used genetic data and two coalescent models to track changes in Japanese eel population size over time.36
The effective population size fell from 38,000 to 10,000 fish between 4 million and 1 million years ago.
It then rose to 80,000 fish between 1 million years ago and 22,000 to 30,000 years ago.
Around 22,000 to 30,000 years ago, it fell again to about 60,000 fish.
Changes in environmental conditions, especially around the last glacial maximum (19,000 to 33,000 years ago), may explain these shifts.
The study indicates at least two population bottlenecks with a growth phase between them.
Overall genetic diversity is low, but the authors found no evidence of inbreeding.
These findings can help estimate the extinction risk of Japanese eel.

European and American Eel Demographics

Assuming a generation length of 13 years (as used in the study for European eels):37

Eel populations stayed large and relatively stable for most of the last 5 million years, with effective population sizes often in the millions.
Both European and American eels experienced a major population decline about 170,000 generations ago (roughly 2.2 million years ago). This decline coincided with the split of the two species from their common ancestor.
A second major decline occurred about 90,000 generations ago (roughly 1.2 million years ago). After this, American eel populations expanded strongly, while European eel populations recovered more slowly and followed a different trajectory for about 30,000 generations.
During the last 30,000 generations (roughly 390,000 years), both species remained remarkably stable despite repeated glacial and interglacial cycles. The sharp declines observed since the 1980s appear unusual against this long history of stability.

Law

UNEP. Single Species Action Plan for the European Eel (Anguilla Anguilla), Annex. UNEP/CMS/Resolution 15.6/Annex. Campo Grande: United Nations Environment Programme, Convention on Migratory Species, Adopted by the Conference of the Parties at its 15th Meeting 2026.

UNEP. Single Species Action Plan for the European Eel (Anguilla Anguilla), Resolution. UNEP/CMS/Resolution 15.6. Campo Grande: United Nations Environment Programme, Convention on Migratory Species, Adopted by the Conference of the Parties at its 15th Meeting 2026.

Proposals and Future

Gansworth, Kristi Leora, and Christopher H. Bowser. “An Anguillid Lens: How Eels Reconnect People and Waterways.” Frontiers in Human Dynamics 5 (2024): 1270644. https://doi.org/10/g3xfxw.

Ethics and Politics

Inoue, Taichi. “Oceans Filled with Agony: Fish Oppression Driven by Capitalist Commodification.” In Animal Oppression and Capitalism, edited by David Alan Nibert, 96–117. Santa Barbara: Praeger, 2017.

Videos

The social and political construction of legality allows eel exploitation to be viewed as both harmful (Asian, illegal markets) and harmless (EU, legal markets), irrespective of the actual harm to the species.38

Eel consumption has been subject to a process of “luxurisation” in northern urban areas, becoming marketed as a delicacy associated with wealth and status, despite eels originally being a food for the masses in Spanish rural areas or Japan.39

The notion of the eel as "dirty" has been re-interiorized within aspirational neoliberal modernity, linking the eel to poverty and the "great unwashed," while also noting that some see the food as irrelevant.40

The modern Japanese culinary "tradition" known as washoku, which centres on rice, fish, and vegetables, has been described as an "invented tradition" with nationalistic or cultural heritage claims. The Japanese government began emphasizing the nation's supposed history as a 'kingdom of fisheries' (suisan ōkoku) in the 1930s to further imperialistic expansion.41 42 43

The mass harvesting and consumption of eels among Māori in New Zealand, often cited in historical records, was a post-European development, suggesting it is a recent cultural shift. Polynesian immigrants brought cultural attitudes to New Zealand associating eels with danger and divine beings, implying that eels were initially not considered food.44

Smuggling

The Black Market for Eels is Exploding

Fishing (aka Killing or Harassing)

See Hutson in Food.

Cassidy, Jim, Irina Ponkratova, and Ben Fitzhugh, eds. Maritime Prehistory of Northeast Asia. Singapore: Springer, 2022.

Projects, Law, and Policy

DIASPARA Project: Unlocking the secrets of Europe's endangered Eel and Salmon

Stein, Florian Martin, Vincent Nijman, Mickey Chung Wai Lau, and Willem Dekker. “Eels: Uncertain Impacts of Proposed CITES Listings.” Oryx 59, no. 1 (2025): 12–13. https://doi.org/10/g9s22k.

Interspecies Relationships

^{"The Biter Bit, (an incident of Bird-life in New Zealand)"}

A Classified List of Mr. S. William Silver’s Collection of New Zealand Birds. With Walter L. Buller. London: E. A. Patherick and Co., 1888, p. 40.

Hosie, E. R. “Cormorant and Eels.” Emu 19, no. 3 (1920): 246. https://doi.org/10/bb747n.

Thomson, Donals. “Cormorant and Eels.” Emu 19, no. 3 (1920): 247. https://doi.org/10/bb747n.

Relationships with Humans

^{A Friendly Eel (16 October 1928)}

Images

^{Knights, S. (Samuel Salkeld) (1852). Natives spearing eels, on Back Creek, 1852.}

References

Arai, Takaomi, ed. Biology and Ecology of Anguillid Eels. Boca Raton: CRC Press, 2016.

Fort, Tom. The Book of Eels: Their Lives, Secrets and Myths. Glasgow: William Collins, 2020.

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Schweid, Richard. Eel. London: Reaktion, 2009.

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Svensson, Patrik. The Book of Eels: Our Enduring Fascination with the Most Mysterious Creature in the Natural World. New York: Ecco, 2020.

Tesch, Friedrich-Wilhelm. The Eel. Edited by John E. Thorpe. Translated by Ray J. White. 3rd ed. Oxford: Blackwell Science, 2003.

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Tsukamoto, Katsumi. Eel Science. Singapore: Springer, 2023.

Notes

Footnotes

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