RiverFish

Flounder · Platichthys flesus

Flounder in the River Ouse

Largest measured flounder: 37.2 cm

The largest flounder measured in Environment Agency surveys of the River Ouse was 37.2 cm, recorded at Naburn Weir (single anode) on 15 July 2002.

Across 221 measured flounder, the median measured length was 15.7 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 Ouse.

See flounder records across England →

Most recent observation7 August 2025Naburn - Fry Survey · 6 fish
Largest measured flounder
37.2 cm
Median length
15.7 cm
Fish measured
221
Survey locations
6

Individual EA measurements

Largest measured flounder

The largest individual measurements in this river and species dataset. Equal measurements are retained as separate surveyed fish.

LengthSurvey dateSurvey locationSurvey ID
37.2 cm15 Jul 2002Naburn Weir (single anode)72809
35.2 cm3 Jul 2006Naburn Weir (single anode)100164
35 cm13 Jul 2001Naburn Weir (single anode)24024
34.5 cm15 Jul 2002Naburn Weir (single anode)72809
34.1 cm7 Jul 2003Naburn Weir (boom boat site)78047
33.2 cm7 Aug 1997Acaster Malbis (boom boat site)110271
31.7 cm7 Jul 2003Naburn Weir (gill net)78050
31.2 cm8 Aug 1997Naburn Weir (single anode)110349
30.5 cm13 Jul 2001Naburn Weir (single anode)24024
30.2 cm28 Jul 2008Naburn Weir (single anode)113010

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

Explore the river

Where flounder were found

Each point marks a survey location with at least one flounder 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 flounder
Naburn - Fry Survey25 Sept 20037 Aug 20259
Naburn Weir (single anode)8 Aug 199721 Jun 201818
Acaster Malbis (single anode)7 Aug 199728 Jun 20138
Naburn Weir (gill net)7 Jul 20037 Jul 20031
Naburn Weir (boom boat site)23 Jul 19997 Jul 20032
Acaster Malbis (boom boat site)7 Aug 19977 Aug 19971

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

1997–2025

Survey records by year

Each bar shows how many survey visits recorded flounder that year.

Fish measured by surveyors

Measured length distribution

See how the 221 measured fish were spread across different length ranges.

Smallest
2 cm
Lower quarter
5.2 cm
Median
15.7 cm
Upper quarter
22.6 cm
Largest
37.2 cm

Lengths are direct survey measurements rather than anglers’ catches.

More fish in this river

Explore the River Ouse

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

Roach Perch Gudgeon Ruffe Bleak Pike

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 →