RiverFish

Brook lamprey · Lampetra planeri

Brook lamprey in the River Glaven

Largest measured brook lamprey: 19.8 cm

The largest brook lamprey measured in Environment Agency surveys of the River Glaven was 19.8 cm, recorded at D/s Hunworth railway bridge on 3 June 2009.

Across 1,444 measured brook lamprey, the median measured length was 13.7 cm.

Surveyors recorded weights for 524 brook lamprey. The median was 0.2 oz (0.0056 kg) and the largest recorded weight was 0.4 oz (0.0127 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 Glaven.

See brook lamprey records across England →

Most recent observation16 June 2026Upstream Glandford Mill · 5 fish
Largest measured brook lamprey
19.8 cm
Median length
13.7 cm
Fish measured
1,444
Survey locations
10

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
19.8 cm3 Jun 2009D/s Hunworth railway bridge121212
19.7 cm3 Jun 2009D/s Hunworth railway bridge121212
19.5 cm18 May 2011D/s Hunworth railway bridge127551
19.2 cm18 May 2011D/s Hunworth railway bridge127551
19.1 cm5 Mar 2009Hunworth Rail Bridge U/s117287
19 cm18 May 2011D/s Hunworth railway bridge127551
18.9 cm3 Jun 2009D/s Hunworth railway bridge121212
18.8 cm20 May 2014Upstream Glandford Mill141006
18.8 cm4 Jun 2009Hunworth Rail Bridge U/s121216
18.6 cm4 Jun 2009Hunworth Rail Bridge U/s121216

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 Glandford Mill18 Mar 199116 Jun 20265
Upstream Thornage Ford4 Apr 199116 May 20258
D/s Hunworth railway bridge12 Jan 19887 May 202514
Upstream Wiveton Bridge13 Jul 199911 Jul 20233
Letheringsett20 Mar 199114 Jun 20236
Thornage Bridge13 Jan 19888 Jun 20237
Hunworth Rail Bridge U/s5 Mar 20095 Jun 20146
Hempstead Mill bridge3 Apr 20083 Apr 20081
Hempstead Hall3 Apr 20083 Apr 20081
Hunworth11 Jan 198822 Jul 19992

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

1988–2026

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 1,444 measured fish were spread across different length ranges.

Smallest
4.1 cm
Lower quarter
11.7 cm
Median
13.7 cm
Upper quarter
15.4 cm
Largest
19.8 cm

Lengths are direct survey measurements rather than anglers’ catches.

Fish weighed by surveyors

Measured weight summary

Recorded weights were available for 524 brook lamprey. This is a subset of the measured fish and may not represent the whole population.

Lightest
0 oz (0.0005 kg)
Lower quarter
0.1 oz (0.0042 kg)
Median
0.2 oz (0.0056 kg)
Upper quarter
0.3 oz (0.0071 kg)
Heaviest
0.4 oz (0.0127 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 Glaven

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

Bullhead 3-spined stickleback European eel Pike Perch Roach

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 →