Direct individual measurements
Largest river lamprey by waterway
Ranked by the largest individual measured in EA surveys. The sample size shows how many valid length measurements underpin each waterway's figures.
| Rank | River or waterway | Largest | Median | Measured | Measured at |
|---|---|---|---|---|---|
| 1 | River HullYorkshire and North East | 36 cm (14.2 in) | 33.8 cm (13.3 in) | 4 | 12 Oct 2005Upstream of Hull Bridge HULLCRS/(LOWER)3 |
| 2 | River Great OuseAnglian | 34.5 cm (13.6 in) | 34.2 cm (13.5 in) | 2 | 28 Oct 2008US Denver Little Eye Sluice |
| 3 | River TillYorkshire and North East | 34 cm (13.4 in) | 34 cm (13.4 in) | 1 | 27 Aug 2015River Till at Twizell Mill |
| 4 | River KeerNorth West | 33.5 cm (13.2 in) | 12 cm (4.7 in) | 17 | 30 Sept 2025High Keer Bridge at Kellet Lane |
| 5 | River Lymn FMUAnglian | 33.4 cm (13.1 in) | 18.5 cm (7.3 in) | 13 | 30 Apr 2003Partney Bridge |
| 6 | River TeesYorkshire and North East | 32.5 cm (12.8 in) | 14 cm (5.5 in) | 26 | 4 Sept 2013Temporal Coarse, Low Moor |
| 7 | River WearYorkshire and North East | 32.5 cm (12.8 in) | 14.6 cm (5.7 in) | 6 | 30 Sept 2009River Wear at Finchale Priory - Eel Site |
| 8 | River Riding MillYorkshire and North East | 32 cm (12.6 in) | 10.5 cm (4.1 in) | 16 | 19 Mar 2008Riding Mill Smolt Trap |
| 9 | King WaterNorth West | 32 cm (12.6 in) | 32 cm (12.6 in) | 1 | 8 Aug 20021283.00 Walton, King Water |
| 10 | River TasAnglian | 32 cm (12.6 in) | 32 cm (12.6 in) | 1 | 19 Apr 2005Downstream Stoke Mill |
Equal maximum lengths are ordered by sample size. Measurements are shown as recorded and are not converted into estimated weights.
1,001 fish measured
Measured river lamprey lengths
The median divides the measured sample in half. This distribution describes surveyed fish, not every river lamprey living in England.
Only positive individual lengths that pass RiverFish's general measurement checks are included. Each bar covers a 20 mm range.
Latest EA evidence
Latest river lamprey observations
The ten most recent survey visits that recorded river lamprey in named waterways.
| Date | River or waterway | Survey location | Fish recorded |
|---|---|---|---|
| 30 Sept 2025 | River Keer | High Keer Bridge at Kellet Lane | 2 |
| 17 Oct 2023 | River Tees | Temporal Coarse, Low Moor | 25 |
| 4 Sept 2023 | River Cumbrian Esk | 1950.10 Golf course, River Esk | Not supplied |
| 26 Jul 2022 | River Keer | High Keer Bridge at Kellet Lane | Not supplied |
| 14 Sept 2021 | River Teme | Milebrook | 1 |
| 1 Sept 2021 | River Lickle | 761.00 Croglinhurst Bridge, R. Lickle | Not supplied |
| 3 Aug 2021 | Lupton Beck | 231.00 Badger Gate | Not supplied |
| 19 Sept 2019 | River Dee | Island, River Dee | 15 |
| 13 Aug 2019 | River Keer | Downstream Keer West Bridge | 4 |
| 22 Oct 2018 | River Wenning | Hornby | 2 |
A survey record confirms river lamprey at that place and time. It does not show present-day abundance or fishing access.
250 positive survey visits
Survey distribution
EA surveys recorded river lamprey at 183 locations across 97 named waterways represented on RiverFish.
| Region | Waterways | Locations | Survey visits | Latest record |
|---|---|---|---|---|
| Yorkshire and North East | 35 | 99 | 148 | 17 Oct 2023 |
| North West | 23 | 29 | 37 | 30 Sept 2025 |
| Midlands | 14 | 19 | 24 | 14 Sept 2021 |
| Anglian | 13 | 24 | 29 | 7 Jul 2017 |
| South West | 10 | 10 | 10 | 17 Aug 2017 |
| South East | 2 | 2 | 2 | 25 Sept 2003 |
12 detailed pages
River lamprey by river
Open any river-specific page for its measured lengths, largest surveyed individuals, locations and observation history.
Anglian 1 pages
Midlands 1 pages
North West 1 pages
Yorkshire and North East 9 pages
How to read this page
Survey measurements, not angling records
Environment Agency surveys are designed to monitor fish populations. Their largest measurement is not equivalent to a verified rod-and-line record, and the survey sample does not include every river or every river lamprey.
Waterway groups with administrative or mixed-river labels are excluded from the headline national totals and rankings. Their eligible river-specific pages remain available in the directory so no published destination is hidden.
The fish records use the Environment Agency source snapshot dated 10 August 2026.
How RiverFish handles the data →