RiverFish

Brook lamprey · Lampetra planeri

Brook lamprey in the River Ruthern

Largest measured brook lamprey: 18 cm

The largest brook lamprey measured in Environment Agency surveys of the River Ruthern was 18 cm, recorded at Ruthern Bridge on 2 July 2013.

Across 34 measured brook lamprey, the median measured length was 10.7 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 Ruthern.

See brook lamprey records across England →

Most recent observation1 July 2026Ruthern Bridge · 2 fish
Largest measured brook lamprey
18 cm
Median length
10.7 cm
Fish measured
34
Survey locations
3

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
18 cm2 Jul 2013Ruthern Bridge136957
15 cm2 Jun 2011Withiel126554
14 cm2 Jul 2013Ruthern Bridge136957
13.9 cm2 Jun 2011Withiel126554
13.7 cm1 Jul 2026Ruthern Bridge182013
13.4 cm1 Jul 2026Ruthern Bridge182013
12.2 cm7 Jun 2023Withiel162532
12 cm2 Jun 2011Withiel126554
11.7 cm24 Jul 2008Ruthern Bridge112149
11.5 cm7 Jun 2023Withiel162532

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
Ruthern Bridge24 Jul 20081 Jul 20265
Trewithian4 Jul 20064 Jul 20233
Withiel6 Jul 20067 Jun 20234

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

2006–2026

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 34 measured fish were spread across different length ranges.

Smallest
5.8 cm
Lower quarter
8.8 cm
Median
10.7 cm
Upper quarter
11.7 cm
Largest
18 cm

Lengths are direct survey measurements rather than anglers’ catches.

More fish in this river

Explore the River Ruthern

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 →