Evidence · Fish & aquatic ecology

The eels have gone — and the tidal ecology "black spot"

The European eel, a Critically Endangered species, has collapsed in the tidal Thames at Richmond: 12 counted in 1993, then a scatter of single fish, and none at all after 2019 — even though the nets kept going out. The wider tidal ecology evidence is patchy in a specific, revealing way.

EA Ecology & Fish Data Explorer Richmond & Teddington · tidal reach WFD body GB530603911403 RAW-PULL

EA seine & kick-net surveys · tidal reach

The headline figures

The Environment Agency has seine- and kick-netted fish at Richmond and Teddington on the tidal Thames since the early 1990s. The long record is the European eel's near-disappearance — set against a fish community that is otherwise still functioning. These are the numbers the raw survey counts give for the reach.

12
European eel counted across the tidal reach in 1993 (Richmond & Teddington seine and kick nets) — the high-water mark for the species here.
EA Fish Data Explorer · TraC fish counts RAW-PULL
2019
the last year a single eel was caught. The reach was surveyed again in 2021, 2022, 2023 and 2025 — zero eels every time.
TraC fish counts, survey years RAW-PULL
~30
every European eel recorded in the whole tidal reach across the entire 1993–2019 record, combined. There is no sign of recovery.
Sum of TraC eel counts DERIVED from RAW-PULL
0
TraC phytoplankton samples anywhere on this reach; macrophytes just 1 site / 2 samples; diatoms stop in 2014. The genuine local evidence gaps.
Reach data-adequacy summary PROVEN GAP

European eel by year, tidal reach, 1992–2025

European eel counted at Richmond & Teddington by year

Individuals caught per year in EA seine and kick-net surveys · tidal Thames (WFD body GB530603911403)

European eel counted per year in the tidal Thames at Richmond and Teddington, 1992 to 2025 Vertical bar chart of European eel individuals caught per survey year. 1993 stands alone at 12 eels. Every later year is far lower: 1994 and 1997 have 3, 1995 has 2, and 1996, 1999, 2002, 2003, 2005, 2007, 2010, 2012, 2015 and 2019 each have just 1. The last eel was recorded in 2019. The reach was surveyed with zero eels caught in 1992, 1998, 2000, 2001, 2004, 2006, 2008, 2009, 2011, 2013, 2014, 2016, 2017, 2018, 2021, 2022, 2023 and 2025; 2020 and 2024 had no survey. The shape is a single early spike followed by near-total absence. 0 3 6 9 12 European eel counted (individuals) Eels caught Surveyed, 0 eels No survey 1993: 12 European eel 1994: 3 European eel 1995: 2 European eel 1996: 1 European eel 1997: 3 European eel 1999: 1 European eel 2002: 1 European eel 2003: 1 European eel 2005: 1 European eel 2007: 1 European eel 2010: 1 European eel 2012: 1 European eel 2015: 1 European eel 2019: 1 European eel — last record 12 3 2 1 3 1 1 1 1 1 1 1 1 1 1992: surveyed, no eel caught 1998: surveyed, no eel caught 2000: surveyed, no eel caught 2001: surveyed, no eel caught 2004: surveyed, no eel caught 2006: surveyed, no eel caught 2008: surveyed, no eel caught 2009: surveyed, no eel caught 2011: surveyed, no eel caught 2013: surveyed, no eel caught 2014: surveyed, no eel caught 2016: surveyed, no eel caught 2017: surveyed, no eel caught 2018: surveyed, no eel caught 2021: surveyed, no eel caught 2022: surveyed, no eel caught 2023: surveyed, no eel caught 2025: surveyed, no eel caught 2020: no fish survey in this reach 2024: no fish survey in this reach Last eel: 2019 none 2020–2025 1992 1995 2000 2005 2010 2015 2020 2025 Survey year (EA seine & kick-net events)
Source: EA Ecology & Fish Data Explorer bulk downloads (TraC fish counts), filtered to the reach and summed by year by this programme. Bars are eels caught; a hollow circle marks a year that was surveyed with no eel caught; a grey cross marks a year with no survey (2020, 2024). Counts mix seine and kick-net gear, so they are indicative abundance, not catch-per-unit-effort. Provenance: RAW-PULL.

The story is a single early spike and then near-absence. Twelve eels in 1993 collapses to a handful of single fish, and the last individual was caught in 2019. Crucially, this is not a monitoring gap: the reach was seine- or kick-netted in 2021, 2022, 2023 and 2025 and caught no eels at all. Across the entire 1992–2025 record only about 30 eels were ever counted in the tidal reach (of which roughly 26 at Richmond). This is consistent with the documented Europe-wide eel collapse — the species is IUCN Critically Endangered, with recruitment down more than 90% since the 1980s.

European eel recorded in the tidal reach — Richmond Seine Net (SITE_ID 20562), Richmond Kick Sample (20560) and Teddington Weir Kick (20625), 1992–2025. Years not listed were surveyed with no eel caught (see chart); 2020 and 2024 had no survey. Provenance: RAW-PULL.
Year European eel (individuals) Note
199312Peak on record — across Richmond & Teddington nets
19943—
19952—
19961—
19973—
19991—
20021—
20031—
20051—
20071—
20101—
20121—
20151—
20191Last eel recorded. None in 2021, 2022, 2023, 2025.

For contrast, freshwater surveys at Molesey (sites 8084/8085, about 6 km above the tidal limit) still catch eels sporadically — a peak of 39 in 2002, then mostly one to three a year — so the disappearance is sharpest in the tidal reach itself. DERIVED from the freshwater fish counts.

The eel aside, the reach's fish community is otherwise still functioning. The 32-year Richmond Seine Net series (98 survey events, 1992–2025; 19,940 fish) is dominated by dace (8,601) and roach (8,055), with flounder (1,354), common goby (622) and sea bass (357), plus scarce smelt and a handful of salmon — an estuarine, diadromous signal, not a dead river. DERIVED from RAW-PULL.

Is the official data good enough / truly open?

The tidal ecology "black spot" — published, but effectively invisible

A common claim about this reach is that the raw tidal fish and ecology data below Teddington (the "TraC" transitional-and-coastal datasets, Mucking → Richmond) is simply not published. Checked against the actual downloads, that claim is largely wrong — and the real failure is more precise, and more interesting, for the question of whether the official evidence base is genuinely usable.

The raw TraC fish counts — including the full 32-year Richmond seine series charted above — are published in the EA's bulk download zips, and so are the raw TraC benthic-invertebrate taxa (100+ samples at Isleworth and Richmond). So this is not an availability failure. What is genuinely missing is the connective tissue:

  • No TraC site-summary metadata. The freshwater datasets each ship a site-summary file (how many samples, first and last dates). The TraC phytoplankton and benthic-invertebrate datasets ship none — so sample counts and date ranges are absent, and the Explorer map cannot filter or surface TraC sites at all. A casual user searching the map concludes "there is no data here," when a 32-year fish series and hundreds of benthic samples sit in the bulk zips. A discoverability / usability failure, not an availability one.
  • One genuine availability gap. TraC phytoplankton is not sampled on this reach at all (0 samples), macrophytes have 1 site / 2 samples (2023–24), and diatoms have 1 site / 6 samples ending in 2014. WFD ecological status for these elements therefore rests on very thin or absent local evidence.
Reach data-adequacy — mainstem Thames, Teddington–Richmond, by WFD biological element. Where an element has one site or none, its classification rests on very thin local evidence. Provenance: DERIVED from RAW-PULL (reach_data_adequacy_summary.csv).
Biological element Mainstem sites Surveys / samples Span
Fish (freshwater / non-tidal)10571995–2025
Fish (TraC / tidal)61421989–2025
Invertebrates (freshwater)61731983–2026
Invertebrates (TraC benthic)22192005–2026
Macrophytes122023–2024
Diatoms (phytobenthos)162007–2014
Phytoplankton (TraC)00none

Highlighted rows are the thin ones: three of the seven WFD biological elements on this reach rest on a single site or no local sampling at all. Fish and invertebrates, by contrast, have long, genuinely useful records — they are just hard to find for the tidal reach.

How to read this

Caveats a regulator would press — stated up front

  • Few monitoring sites; the reach evidence is thin. The tidal eel picture rests on essentially two Richmond netting stations plus a single early Teddington site. A handful of stations and a few dozen eels over 30 years is a real signal, but a small one — treat it as indicative, not a precise census.
  • Effort is not standardised. Raw counts mix seine netting, kick-netting and electrofishing across years, so year-to-year totals are indicative abundance, not catch-per-unit-effort. Do not read fine differences (a 1 vs a 3) as trend.
  • "None after 2019" means "none in the years surveyed." The absence is real — the reach was netted in 2021, 2022, 2023 and 2025 with zero eels — but 2020 and 2024 had no survey at all, shown as grey crosses on the chart.
  • The eel collapse is international, not local. European eel recruitment is down >90% Europe-wide (IUCN Critically Endangered); this reach mirrors a continental decline. It is a wildlife-harm signal — it does not, on its own, prove a local cause or attribute the decline to any one discharger.
  • "TraC data is unpublished" is wrong. The raw TraC fish and benthic-invertebrate data are in the open downloads. The honest, defensible criticism is the missing site-summary metadata and map filter (a usability gap) plus the one real gap — no TraC phytoplankton sampling here. We state it that way and do not overclaim.
  • Tidal biology is otherwise healthy. Under estuarine WFD tools the reach's fish and invertebrates score Good/High; its Moderate status is driven by chemistry and hydromorphology, not a dead biological community. The eel is one struggling species within a still-working assemblage.
  • Waterbody-code note. The fish and benthic TraC datasets use GB530603911403 for the tidal Thames here; the WFD-status page cites "Thames Middle" GB530603911402. These need reconciling (operational-catchment vs water-body coding) before any cross-page claim is made.

Sources & provenance

  • RAW-PULL  EA Ecology & Fish Data Explorer — bulk downloads https://environment.data.gov.uk/ecology/explorer/downloads/ (documentation /ecology/explorer/how-to-use/). National zips downloaded 2026-07-31 (files dated 2026-07-05/06), filtered to the reach bounding box (lat 51.40–51.48, lon −0.35 to −0.28; OSGB→WGS84 via pyproj). Open Government Licence; England only.
  • Tidal sites: Richmond Seine Net SITE_ID 20562 (98 events, 1992–2025), Richmond Kick Sample 20560 (37 events), Teddington Weir Kick 20625; WFD body GB530603911403. Freshwater contrast: Molesey 8084/8085, ~6 km above Teddington.
  • Working files: /tmp/thames_datastore/fish_ecology/reach_TRAC_fish_counts.csv, reach_FW_fish_counts.csv, reach_data_adequacy_summary.csv, reach_sites_TRAC.csv, and the domain NOTE.md.
  • Conservation status: European eel (Anguilla anguilla) — IUCN Critically Endangered; >90% fall in European recruitment since the 1980s. PUBLISHED