Brook lamprey · Lampetra planeri

Brook lamprey in the River Mimram

Largest measured brook lamprey: 17.9 cm

The largest brook lamprey measured in Environment Agency surveys of the River Mimram was 17.9 cm, recorded at Panshanger quarry on 11 October 2018.

Across 61 measured brook lamprey, the median measured length was 14.8 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 Mimram.

See brook lamprey records across England →

Most recent observation25 September 2025Tewin Flyfishers

Largest measured brook lamprey: 17.9 cm
Median length: 14.8 cm
Fish measured: 61
Survey locations: 4

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.

Length	Survey date	Survey location	Survey ID
17.9 cm	11 Oct 2018	Panshanger quarry	153753
17.9 cm	11 Oct 2018	Panshanger quarry	153753
17.5 cm	23 Sept 2019	Tewin Flyfishers	155723
17.2 cm	17 Oct 2019	Panshanger quarry	155850
17.2 cm	11 Oct 2018	Panshanger quarry	153753
16.9 cm	17 Oct 2019	Panshanger quarry	155850
16.8 cm	11 Oct 2018	Panshanger quarry	153753
16.7 cm	23 Sept 2019	Tewin Flyfishers	155723
16.7 cm	11 Oct 2018	Panshanger quarry	153753
16.5 cm	11 Oct 2018	Panshanger quarry	153753

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 surveyed	First recorded	Last recorded	Visits finding brook lamprey
Tewin Flyfishers	23 Sept 2019	25 Sept 2025	3
Panshanger quarry	26 Apr 2007	2 Sept 2025	8
Tewin Archers	3 Oct 2017	23 Sept 2019	2
Tewin flyfishers middle	16 Oct 2018	16 Oct 2018	1

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

2007–2025

Survey records by year

Each bar shows how many survey visits recorded brook lamprey that year.

107

008

009

010

111

012

013

014

015

016

217

218

319

020

021

022

223

124

225

Fish measured by surveyors

Measured length distribution

See how the 61 measured fish were spread across different length ranges.

Smallest: 9.5 cm
Lower quarter: 13.2 cm
Median: 14.8 cm
Upper quarter: 16.1 cm
Largest: 17.9 cm

0–99 mm

100–199 mm

Lengths are direct survey measurements rather than anglers’ catches.

More fish in this river

Explore the River Mimram

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

Bullhead Brown / sea trout Stone loach 3-spined stickleback Minnow 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 →