RiverFish

Brook lamprey · Lampetra planeri

Brook lamprey in the River Wensum (Restoration strategy)

Largest measured brook lamprey: 17.8 cm

The largest brook lamprey measured in Environment Agency surveys of the River Wensum (Restoration strategy) was 17.8 cm, recorded at Three Bridges Farm, Lyng on 22 August 2024.

Across 67 measured brook lamprey, the median measured length was 13.2 cm.

Surveyors recorded weights for 9 brook lamprey. The median was 0.1 oz (0.003 kg) and the largest recorded weight was 0.2 oz (0.005 kg).

RiverFish uses Environment Agency survey measurements rather than rod-and-line angling records. These figures show fish measured during EA surveys of the River Wensum (Restoration strategy).

See brook lamprey records across England →

Most recent observation1 May 2025Upstream Dunton Bridge · 3 fish
Largest measured brook lamprey
17.8 cm
Median length
13.2 cm
Fish measured
67
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
17.8 cm22 Aug 2024Three Bridges Farm, Lyng167129
16.8 cm22 Jul 2013Gt. Ryburgh Common, New loop (Reach24)137469
16.7 cm22 Aug 2024Three Bridges Farm, Lyng167129
16.3 cm16 Apr 2019Upstream Dunton Bridge155907
16.2 cm8 Jul 2019Hempton Moor (Upstream Fakenham bypass) (reach 27)156033
16 cm26 Jul 2013Downstream Fakenham Common (Reach 25)137482
16 cm22 Jul 2013Gt. Ryburgh Common, New loop (Reach24)137469
15.8 cm16 Apr 2019Upstream Dunton Bridge155907
15.8 cm22 Jul 2014Downstream Fakenham Common (Reach 25)142750
15.7 cm22 Jul 2014Downstream Fakenham Common (Reach 25)142750

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
Upstream Dunton Bridge6 Apr 20171 May 20253
Swanton Morley (Restoration Reach 14)28 Aug 202428 Aug 20241
Three Bridges Farm, Lyng22 Aug 202422 Aug 20241
Hempton Moor (Upstream Fakenham bypass) (reach 27)5 Sept 20158 Jul 20192
Downstream Fakenham Common (Reach 25)26 Jul 201322 Jul 20142
Gt. Ryburgh Common, New loop (Reach24)22 Jul 201322 Jul 20131
Upstream County School (reach 19)21 Sept 20094 Sept 20123

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

2009–2025

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 67 measured fish were spread across different length ranges.

Smallest
6.5 cm
Lower quarter
12 cm
Median
13.2 cm
Upper quarter
14.6 cm
Largest
17.8 cm

Lengths are direct survey measurements rather than anglers’ catches.

Fish weighed by surveyors

Measured weight summary

Recorded weights were available for 9 brook lamprey. This is a subset of the measured fish and may not represent the whole population.

Lightest
0.1 oz (0.002 kg)
Lower quarter
0.1 oz (0.002 kg)
Median
0.1 oz (0.003 kg)
Upper quarter
0.1 oz (0.003 kg)
Heaviest
0.2 oz (0.005 kg)

These are direct individual weights recorded by Environment Agency surveyors. Combined bulk weights are not included.

More fish in this river

Explore the River Wensum (Restoration strategy)

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

Minnow Bullhead Dace Stone loach Gudgeon 3-spined stickleback

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 →