Individual EA measurements
Largest measured perch
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 |
|---|---|---|---|
| 39.4 cm | 4 Jun 2013 | Upstream Coppermill Lock to Springwell Lock | 136266 |
| 39.2 cm | 4 Jun 2013 | Upstream Coppermill Lock to Springwell Lock | 136266 |
| 34.5 cm | 9 Mar 1988 | Cassiobury Park u/s Lock | 116407 |
| 34.2 cm | 26 Apr 1988 | Slough Arm at Iver North STW | 116487 |
| 33.3 cm | 5 Nov 1987 | Stockley Road | 116118 |
| 32.5 cm | 31 Mar 1987 | Berkhamsted | 116251 |
| 31 cm | 31 Mar 1987 | Berkhamsted | 116251 |
| 30.9 cm | 8 Mar 1988 | Stockers Farm | 116413 |
| 30.3 cm | 18 Mar 1988 | Coppermill Lane, Rickmansworth | 116490 |
| 29.8 cm | 5 Nov 1987 | Stockley Road | 116118 |
Lengths are direct survey measurements. RiverFish does not estimate fish weights from length.
Explore the river
Where perch were found
Each point marks a survey location with at least one perch 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 perch |
|---|---|---|---|
| Springwell Backwater | 16 Sept 2013 | 16 Sept 2013 | 1 |
| u/s Widewater Lock | 4 Jun 2013 | 4 Jun 2013 | 1 |
| Upstream Coppermill Lock to Springwell Lock | 4 Jun 2013 | 4 Jun 2013 | 1 |
| Slough Arm at Iver North STW | 26 Apr 1988 | 26 Apr 1988 | 1 |
| Hunton Bridge | 21 Apr 1988 | 21 Apr 1988 | 1 |
| Hanwell | 29 Mar 1988 | 29 Mar 1988 | 1 |
| Kensal Road | 25 Mar 1988 | 25 Mar 1988 | 1 |
| Victoria Park | 23 Mar 1988 | 23 Mar 1988 | 1 |
| Coppermill Lane, Rickmansworth | 18 Mar 1988 | 18 Mar 1988 | 1 |
| Cassiobury Park u/s Lock | 9 Mar 1988 | 9 Mar 1988 | 1 |
| Stockers Farm | 8 Mar 1988 | 8 Mar 1988 | 1 |
| Winkwell Lane, Bourne End | 3 Mar 1988 | 3 Mar 1988 | 1 |
| Slough Arm at B470 Road | 29 Feb 1988 | 29 Feb 1988 | 1 |
| Stockley Road | 5 Nov 1987 | 5 Nov 1987 | 1 |
| Horsendon Lane | 5 Jun 1987 | 5 Jun 1987 | 1 |
| Bankside | 3 Jun 1987 | 3 Jun 1987 | 1 |
| The Common | 13 May 1987 | 13 May 1987 | 1 |
| Berkhamsted | 31 Mar 1987 | 31 Mar 1987 | 1 |
| Johnsons Lock | 17 Mar 1987 | 17 Mar 1987 | 1 |
| York Way | 9 Dec 1986 | 9 Dec 1986 | 1 |
Choose a point or table row to see the location. More survey visits can mean more records, but not necessarily more fish.
1986–2013
Survey records by year
Each bar shows how many survey visits recorded perch that year.
Fish measured by surveyors
Measured length distribution
See how the 430 measured fish were spread across different length ranges.
- Smallest
- 0.8 cm
- Lower quarter
- 7 cm
- Median
- 11.8 cm
- Upper quarter
- 18.2 cm
- Largest
- 39.4 cm
Lengths are direct survey measurements rather than anglers’ catches.
Fish weighed by surveyors
Measured weight summary
Recorded weights were available for 345 perch. This is a subset of the measured fish and may not represent the whole population.
- Lightest
- 0 oz (0.001 kg)
- Lower quarter
- 0.6 oz (0.017 kg)
- Median
- 1.3 oz (0.036 kg)
- Upper quarter
- 4.6 oz (0.131 kg)
- Heaviest
- 1 lb 15.7 oz (0.9 kg)
These are direct individual weights recorded by Environment Agency surveyors. Combined bulk weights are not included.
More fish in this river
Explore the Grand Union Canal
Compare other species with enough survey and measurement data for a detailed page.
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 →