Sea lamprey · Petromyzon marinus

Sea lamprey in the River Main Tamar

Largest measured sea lamprey: 88.6 cm

The largest sea lamprey measured in Environment Agency surveys of the River Main Tamar was 88.6 cm, recorded at Gunnislake Weir Index River Fish Trap on 31 May 2012.

Across 214 measured sea lamprey, the median measured length was 75.5 cm.

Surveyors recorded weights for 214 sea lamprey. The median was 2 lb 0.8 oz (0.93 kg) and the largest recorded weight was 4 lb 2 oz (1.87 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 Main Tamar.

See sea lamprey records across England →

Most recent observation19 June 2018Gunnislake Weir Index River Fish Trap · 1 fish

Largest measured sea lamprey: 88.6 cm
Median length: 75.5 cm
Fish measured: 214
Survey locations: 1

Individual EA measurements

Largest measured sea 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
88.6 cm	31 May 2012	Gunnislake Weir Index River Fish Trap	159111
87.5 cm	3 Jun 2015	Gunnislake Weir Index River Fish Trap	159514
87.5 cm	24 May 2012	Gunnislake Weir Index River Fish Trap	159105
87.5 cm	24 May 2012	Gunnislake Weir Index River Fish Trap	159105
87.5 cm	21 May 2012	Gunnislake Weir Index River Fish Trap	159101
87 cm	20 Jun 2017	Gunnislake Weir Index River Fish Trap	159676
86 cm	31 May 2017	Gunnislake Weir Index River Fish Trap	159667
86 cm	2 Jun 2016	Gunnislake Weir Index River Fish Trap	159597
85.5 cm	7 May 2013	Gunnislake Weir Index River Fish Trap	159346
85.5 cm	24 May 2012	Gunnislake Weir Index River Fish Trap	159105

Lengths are direct survey measurements. RiverFish does not estimate fish weights from length.

Explore the river

Where sea lamprey were found

Each point marks a survey location with at least one sea 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 sea lamprey
Gunnislake Weir Index River Fish Trap	12 Jun 2011	19 Jun 2018	57

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

2011–2018

Survey records by year

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

211

2512

513

014

515

1116

517

418

Fish measured by surveyors

Measured length distribution

See how the 214 measured fish were spread across different length ranges.

Smallest: 60.5 cm
Lower quarter: 71 cm
Median: 75.5 cm
Upper quarter: 79.7 cm
Largest: 88.6 cm

600–699 mm

700–799 mm

122

800–899 mm

Lengths are direct survey measurements rather than anglers’ catches.

Fish weighed by surveyors

Measured weight summary

Recorded weights were available for 214 sea lamprey. This is a subset of the measured fish and may not represent the whole population.

Lightest: 2.8 oz (0.08 kg)
Lower quarter: 1 lb 12.2 oz (0.8 kg)
Median: 2 lb 0.8 oz (0.93 kg)
Upper quarter: 2 lb 5.7 oz (1.07 kg)
Heaviest: 4 lb 2 oz (1.87 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 Main Tamar

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

Bullhead Stone loach Atlantic salmon Brown / sea trout Minnow European eel

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 →