Rainbow trout · Oncorhynchus mykiss

Rainbow trout in the River Box (Main Reaches)

Largest measured rainbow trout: 37.6 cm

The largest rainbow trout measured in Environment Agency surveys of the River Box (Main Reaches) was 37.6 cm, recorded at Polstead Mill on 17 May 2018.

Across 28 measured rainbow trout, the median measured length was 31.4 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 Box (Main Reaches).

See rainbow trout records across England →

Most recent observation17 May 2024Scotland Street · 1 fish

Largest measured rainbow trout: 37.6 cm
Median length: 31.4 cm
Fish measured: 28
Survey locations: 5

Individual EA measurements

Largest measured rainbow trout

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
37.6 cm	17 May 2018	Polstead Mill	152674
36.3 cm	17 May 2024	Scotland Street	165731
36.3 cm	31 May 2018	Thorington Mill	152769
33.7 cm	6 May 2015	Polstead Ford	144663
33.5 cm	15 Apr 2015	Thorington Mill	144750
33.2 cm	27 Mar 1985	Polstead Mill	13776
32.9 cm	10 Apr 1991	Stour Confluence	13785
32.6 cm	31 May 2018	Thorington Mill	152769
32.2 cm	31 May 2018	Thorington Mill	152769
32.2 cm	16 May 2006	Thorington Mill	100293

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

Explore the river

Where rainbow trout were found

Each point marks a survey location with at least one rainbow trout 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 rainbow trout
Scotland Street	18 May 2006	17 May 2024	2
Thorington Mill	2 May 1997	31 May 2018	5
Stour Confluence	10 Apr 1991	30 May 2018	3
Polstead Mill	27 Mar 1985	17 May 2018	2
Polstead Ford	6 May 2015	6 May 2015	1

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

1985–2024

Survey records by year

Each bar shows how many survey visits recorded rainbow trout that year.

185

086

087

088

089

090

191

092

093

094

095

096

297

098

099

100

001

002

003

004

005

206

007

008

009

010

011

012

013

014

215

016

017

318

019

020

021

022

023

124

Fish measured by surveyors

Measured length distribution

See how the 28 measured fish were spread across different length ranges.

Smallest: 29.6 cm
Lower quarter: 30.6 cm
Median: 31.5 cm
Upper quarter: 32.7 cm
Largest: 37.6 cm

200–299 mm

300–399 mm

Lengths are direct survey measurements rather than anglers’ catches.

More fish in this river

Explore the River Box (Main Reaches)

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

European eel Brown / sea trout Stone loach Dace Roach Chub

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 →