RiverFish

Brook lamprey · Lampetra planeri

Brook lamprey in the River Wensum (upper)

Largest measured brook lamprey: 18 cm

The largest brook lamprey measured in Environment Agency surveys of the River Wensum (upper) was 18 cm, recorded at Upstream Sculthorpe Mill on 3 May 2024.

Across 161 measured brook lamprey, the median measured length was 13.3 cm.

Surveyors recorded weights for 65 brook lamprey. The median was 0.2 oz (0.005 kg) and the largest recorded weight was 0.4 oz (0.01 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 (upper).

See brook lamprey records across England →

Most recent observation22 April 2025Tatterford Common · 9 fish
Largest measured brook lamprey
18 cm
Median length
13.3 cm
Fish measured
161
Survey locations
9

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 cm3 May 2024Upstream Sculthorpe Mill166210
17.2 cm18 Apr 2023Hellhoughton Common162544
16.9 cm14 Jun 2018Fakenham Common152922
16.8 cm14 Jun 2018Fakenham Common152922
16.5 cm8 Jun 2018Upstream Sculthorpe Mill152888
16.3 cm14 Jun 2018Fakenham Common152922
16.2 cm21 May 2018South Mill Farm152798
16.2 cm14 Oct 2009Fakenham Common119378
15.8 cm4 May 2023Upstream Broomsthorpe Bridge162623
15.8 cm10 Mar 2022Upstream Broomsthorpe Bridge160989

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
Tatterford Common24 Apr 199022 Apr 20258
Upstream Broomsthorpe Bridge23 Apr 199015 Apr 20258
Hellhoughton Common10 Apr 199010 Apr 20255
Upstream Sculthorpe Mill30 Apr 19903 May 202410
Upstream Fakenham Mill19 Mar 198611 Apr 20199
Fakenham Common20 Mar 198614 Jun 20187
South Mill Farm26 Feb 198621 May 20188
Downstream Doughton Bridge27 Apr 19903 Apr 19973
Upstream Raynham Bridge9 Apr 199026 Mar 19972

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

1986–2025

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 161 measured fish were spread across different length ranges.

Smallest
5.3 cm
Lower quarter
12.2 cm
Median
13.3 cm
Upper quarter
14.2 cm
Largest
18 cm

Lengths are direct survey measurements rather than anglers’ catches.

Fish weighed by surveyors

Measured weight summary

Recorded weights were available for 65 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 (0.004 kg)
Median
0.2 oz (0.005 kg)
Upper quarter
0.2 oz (0.007 kg)
Heaviest
0.4 oz (0.01 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 (upper)

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

Brown / sea trout Stone loach Bullhead European eel 3-spined stickleback 10-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 →