Brook lamprey · Lampetra planeri

Brook lamprey in the River Wensum (central)

Largest measured brook lamprey: 18.5 cm

The largest brook lamprey measured in Environment Agency surveys of the River Wensum (central) was 18.5 cm, recorded at Downstream Elsing Mill on 28 September 2017.

Across 217 measured brook lamprey, the median measured length was 14.1 cm.

Surveyors recorded weights for 97 brook lamprey. The median was 0.2 oz (0.006 kg) and the largest recorded weight was 0.4 oz (0.011 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 (central).

See brook lamprey records across England →

Most recent observation10 September 2025Swanton Morley · 1 fish

Largest measured brook lamprey: 18.5 cm
Median length: 14.1 cm
Fish measured: 217
Survey locations: 26

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
18.5 cm	28 Sept 2017	Downstream Elsing Mill	152396
17.8 cm	5 Sept 2013	Downstream Gt Ryburgh Bridge	138561
17.7 cm	31 Jul 2019	Downstream Gt Ryburgh Bridge	156038
17.5 cm	10 Oct 2017	Downstream Gt Ryburgh Bridge	152404
17.2 cm	28 Sept 2017	Downstream Elsing Mill	152396
16.9 cm	7 Sept 2016	Downstream Gt Ryburgh Bridge	150021
16.8 cm	28 Sept 2017	Downstream Elsing Mill	152396
16.8 cm	21 Aug 2012	Downstream Elsing Mill	132960
16.8 cm	28 Sept 2009	Upstream Gt Ryburgh	119201
16.6 cm	5 Sept 2013	Downstream Gt Ryburgh Bridge	138561

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
Swanton Morley	14 Jun 1994	10 Sept 2025	8
Alders Spinney	19 Sept 2005	14 Aug 2025	9
Downstream Elsing Mill	14 May 1997	7 Aug 2025	11
Downstream Gt Ryburgh Bridge	9 Jun 1986	1 Aug 2025	17
Sparham pool, Lyng	19 Oct 2017	6 Sept 2024	4
Upstream Bintree Mill	29 Sept 2003	22 Aug 2012	3
Pensthorpe Hall	10 Jun 1986	13 Oct 2009	5
Upstream Drayton Green Lane	28 Aug 1990	8 Oct 2009	3
Lyng Pits	25 Sept 2003	1 Oct 2009	2
Downstream Ringland Bridge	3 Jun 1997	30 Sept 2009	3
Upstream Gt Ryburgh	22 Apr 1997	28 Sept 2009	3
Attlebridge Hall Farm	24 Sept 2003	23 Sept 2009	2
Upstream Lenwade Mill	1 Oct 2003	22 Sept 2009	2
Downstream Billingford Bridge	4 Sept 2003	15 Sept 2008	3
Hellesdon Road (Albert's)	10 Oct 2003	22 Sept 2005	3
Downstream Attlebridge Bridge	22 Sept 2003	22 Sept 2003	1
Blakes Meadow	17 Sept 2003	17 Sept 2003	1
County School	7 Jun 1994	10 Sept 2003	3
Heigham Waterworks	5 Aug 1997	5 Aug 1997	1
Downstream Point Costessey	9 Jul 1997	9 Jul 1997	1
Walcis Farm	6 Jun 1997	6 Jun 1997	1
Swan Rescue	5 Jun 1997	5 Jun 1997	1
Upstream Elsing Mill	13 May 1997	13 May 1997	1
Sennowe Park	13 Jul 1990	24 Apr 1997	2
Downstream Broken Bridges	24 Aug 1990	24 Aug 1990	1
Upstream Costessey Mill	21 Aug 1990	21 Aug 1990	1

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.

286

087

088

089

490

091

092

093

394

095

096

1297

098

099

000

001

002

1603

304

405

006

007

308

1109

410

111

412

113

114

215

416

417

018

419

020

021

222

123

224

425

Fish measured by surveyors

Measured length distribution

See how the 217 measured fish were spread across different length ranges.

Smallest: 10 cm
Lower quarter: 12.9 cm
Median: 14.1 cm
Upper quarter: 15.1 cm
Largest: 18.5 cm

100–199 mm

217

Lengths are direct survey measurements rather than anglers’ catches.

Fish weighed by surveyors

Measured weight summary

Recorded weights were available for 97 brook lamprey. This is a subset of the measured fish and may not represent the whole population.

Lightest: 0.1 oz (0.003 kg)
Lower quarter: 0.2 oz (0.0045 kg)
Median: 0.2 oz (0.006 kg)
Upper quarter: 0.3 oz (0.008 kg)
Heaviest: 0.4 oz (0.011 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 (central)

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

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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 →