RiverFish

Brook lamprey · Lampetra planeri

Brook lamprey in the River Medway

Largest measured brook lamprey: 16.2 cm

The largest brook lamprey measured in Environment Agency surveys of the River Medway was 16.2 cm, recorded at Penshurst on 19 September 2024.

Across 54 measured brook lamprey, the median measured length was 13.2 cm.

Surveyors recorded weights for 3 brook lamprey. The median was 0.2 oz (0.005 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 Medway.

See brook lamprey records across England →

Most recent observation16 October 2025Penshurst · 14 fish
Largest measured brook lamprey
16.2 cm
Median length
13.2 cm
Fish measured
54
Survey locations
6

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
16.2 cm19 Sept 2024Penshurst168393
15.5 cm19 Sept 2024Penshurst168393
15.5 cm19 Sept 2024Penshurst168393
15 cm19 Sept 2024Penshurst168393
15 cm26 Jul 2023Penshurst163085
15 cm19 Sept 2006Bewleys Weir103377
14.9 cm19 Sept 2024Penshurst168393
14.8 cm19 Sept 2024Penshurst168393
14.7 cm19 Sept 2024Penshurst168393
14.6 cm19 Sept 2024Penshurst168393

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
Penshurst6 Sept 200616 Oct 20255
Fordcombe8 Aug 202315 Oct 20252
Hartfield27 Jul 200615 Oct 20242
D/s Ashurst Road Bridge18 Sept 202418 Sept 20241
Grom/Medway Confluence u/s9 Oct 20079 Oct 20071
Bewleys Weir19 Sept 200619 Sept 20061

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 54 measured fish were spread across different length ranges.

Smallest
7 cm
Lower quarter
12.6 cm
Median
13.2 cm
Upper quarter
14.5 cm
Largest
16.2 cm

Lengths are direct survey measurements rather than anglers’ catches.

Fish weighed by surveyors

Measured weight summary

Recorded weights were available for 3 brook lamprey. This is a subset of the measured fish and may not represent the whole population.

Lightest
0.1 oz (0.004 kg)
Lower quarter
0.2 oz (0.0045 kg)
Median
0.2 oz (0.005 kg)
Upper quarter
0.2 oz (0.005 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 Medway

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

Chub Gudgeon Roach Perch Bleak Dace

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 →