RiverFish

Brook lamprey · Lampetra planeri

Brook lamprey in the River Main Allen

Largest measured brook lamprey: 13.5 cm

The largest brook lamprey measured in Environment Agency surveys of the River Main Allen was 13.5 cm, recorded at Dinhams Bridge on 21 June 2023.

Across 84 measured brook lamprey, the median measured length was 10.3 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 Allen.

See brook lamprey records across England →

Most recent observation14 August 2025Trehannick · 7 fish
Largest measured brook lamprey
13.5 cm
Median length
10.3 cm
Fish measured
84
Survey locations
7

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
13.5 cm21 Jun 2023Dinhams Bridge162560
13.3 cm13 Jul 2011Lamellan126967
13 cm27 Sept 2011Trehannick Saw Mill (restored)129223
13 cm12 Jul 2011Trehannick126977
12.8 cm27 Sept 2011Trehannick Saw Mill (restored)129223
12.5 cm14 Aug 2025Trehannick179143
12.5 cm19 Jul 2024Trehannick166845
12.4 cm13 Jul 2011Littlewood Mill126974
12.1 cm13 Jul 2011Littlewood Mill126974
12 cm14 Aug 2025Trehannick179143

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
Trehannick25 Jul 200614 Aug 202511
Upstream Littlewood Mill10 Aug 202310 Aug 20231
Treforda15 Aug 20177 Aug 20232
Dinhams Bridge14 Jul 201121 Jun 20232
Littlewood Mill7 Aug 200627 Jul 20184
Trehannick Saw Mill (restored)27 Sept 201127 Sept 20111
Lamellan13 Jul 201113 Jul 20111

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 84 measured fish were spread across different length ranges.

Smallest
4.7 cm
Lower quarter
8.2 cm
Median
10.3 cm
Upper quarter
11.5 cm
Largest
13.5 cm

Lengths are direct survey measurements rather than anglers’ catches.

More fish in this river

Explore the River Main Allen

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

Brown / sea trout Bullhead European eel Atlantic salmon

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 →