RiverFish

Brook lamprey · Lampetra planeri

Brook lamprey in the River Main Inny

Largest measured brook lamprey: 17 cm

The largest brook lamprey measured in Environment Agency surveys of the River Main Inny was 17 cm, recorded at Trewinnow on 24 September 2021.

Across 282 measured brook lamprey, the median measured length was 10.6 cm.

RiverFish uses Environment Agency survey measurements rather than rod-and-line angling records. These figures show fish measured during EA surveys of the River Main Inny.

See brook lamprey records across England →

Most recent observation21 August 2025U/s Davidstow Creamery Discharge · 28 fish
Largest measured brook lamprey
17 cm
Median length
10.6 cm
Fish measured
282
Survey locations
12

Individual EA measurements

Largest measured brook lamprey

The largest individual measurements in this river and species dataset. Equal measurements are retained as separate surveyed fish.

LengthSurvey dateSurvey locationSurvey ID
17 cm24 Sept 2021Trewinnow160424
15.3 cm24 Jun 2015Knightsmill145147
14.5 cm18 Jun 2015Larrick145089
14.2 cm18 Jun 2015Larrick145089
14.2 cm23 Jun 2014Treguddick Mill141294
14 cm13 Aug 2021U/s Inny Vale STW160421
14 cm19 Jul 2021Trewen160432
14 cm28 Aug 2013Bealsmill138202
13.9 cm24 Jun 2015Knightsmill145147
13.8 cm19 Jul 2021Trewen160432

Lengths are direct survey measurements. RiverFish does not estimate fish weights from length.

Explore the river

Where brook lamprey were found

Each point marks a survey location with at least one brook lamprey record.

Choose a point on the map to see what was recorded there.

Map points are approximate and don’t show fishing access. Check local permissions before visiting.

Place surveyedFirst recordedLast recordedVisits finding brook lamprey
U/s Davidstow Creamery Discharge11 Aug 202121 Aug 20252
Trewinnow27 Aug 200912 Aug 20255
Treguddick Mill16 Jun 201022 Jul 20259
Trecarrell1 Sept 200922 Sept 20212
St. Clether24 Jun 200921 Sept 20215
Bealsmill4 Jun 200926 Aug 20216
U/s Inny Vale STW13 Aug 202113 Aug 20211
Larrick5 Jun 200928 Jul 20213
Knightsmill10 Jun 200922 Jul 20213
Trewen9 Jun 200919 Jul 20213
u/s Laneast Bridge17 Jun 200916 Jul 20213
Treguddick18 Jul 200612 Sept 20072

Choose a point or table row to see the location. More survey visits can mean more records, but not necessarily more fish.

2006–2025

Survey records by year

Each bar shows how many survey visits recorded brook lamprey that year.

Fish measured by surveyors

Measured length distribution

See how the 282 measured fish were spread across different length ranges.

Smallest
5.2 cm
Lower quarter
9.4 cm
Median
10.6 cm
Upper quarter
12 cm
Largest
17 cm

Lengths are direct survey measurements rather than anglers’ catches.

More fish in this river

Explore the River Main Inny

Compare other species with enough survey and measurement data for a detailed page.

Atlantic salmon Brown / sea trout Bullhead Stone loach European eel Minnow

Before you fish

Good to know

These are past survey records, so the fish present today may be different. Map points are approximate—check local access, permissions and fishing rules before visiting.

Learn how RiverFish uses the data →