| Grade |
Description |
Interpretation |
| A |
Excellent |
In the top 20% for a fishery of this type |
| B |
Good |
In the top 40% for a fishery of this type |
| C |
Fair |
In the middle 20% for a fishery of this type |
| D |
Fair |
In the bottom 40% for a fishery of this type |
| E |
Poor |
In the bottom 20% for a fishery of this type |
| F |
Fishless |
No fish of this type present |
How is fish density on the Avon graded?
- From 2002 to 2006 inclusive the site on the Avon at Avonwick Mill (now named Turtley Corn Mill) was fished between stop nets and each survey consisted of 3 runs
- From 2007 onwards the site has been fished using no stop nets and only one run (The Environment Agency National Fish Population Database (NFPD) automatically adjusts the figures for the one-run surveys and produces the results as if they had fished the site using 3 runs between stop nets)
- The same site is fished every year and is fished in an upstream direction using electric fishing kit producing a Pulsed Direct Current of approximately 0.3amps
The number of fish caught is expressed as the density of fish per 100 square meters -100m. This value is then converted into a grade using the following conversion table:
| |
|
A |
B |
C |
D |
E |
| |
Age |
Density of fish per 100 square meters -100m |
| Brown/Sea Trout |
0+ |
>38 |
17 to 37 |
8 to 16 |
3 to 7 |
<3 |
| Brown/Sea Trout |
>0+ |
>21 |
12 to 20 |
5 to 11 |
2 to 4 |
<2 |
| Salmon |
0+ |
>86 |
45 to 85 |
23 to 44 |
9 to 22 |
<9 |
| Salmon |
>0+ |
>19 |
10 to 18 |
5 to 9 |
3 to 4 |
<3 |
- In the next set of tables, population density is expressed in two ways:
- Density of fish per 100 square meters -100m
- and as the corresponding National Fishery Classification Scheme grade – from A through F
- The data from three local rivers – the Avon, Erme and Yealm is presented below for comparison
- EA data kindly supplied by Mike Cooper and Stuart Watts, Aune Conservation Association
| Avon – Glazebrook Avonwick Mill |
| Year |
Trout Fry density |
Grade |
Trout Parr density |
Grade |
Salmon Fry density |
Grade |
Salmon Parr density |
Grade |
| 2002 |
5.68 |
D |
4.39 |
D |
8.51 |
E |
5.93 |
C |
| 2003 |
11.87 |
C |
12.84 |
B |
40.12 |
C |
8.99 |
C |
| 2004 |
12.02 |
C |
18.35 |
B |
27.2 |
C |
9.81 |
C |
| 2005 |
8.52 |
C |
16.19 |
B |
10.51 |
D |
6 |
C |
| 2006 |
18.62 |
B |
19.3 |
B |
33.18 |
C |
6.77 |
C |
| 2007 |
11.13 |
C |
12.11 |
B |
33.38 |
C |
8.51 |
C |
| 2008 |
9.58 |
C |
9.3 |
C |
27.63 |
C |
11.56 |
B |
| 2009 |
10.27 |
C |
10.61 |
C |
78.03 |
B |
11.98 |
B |
|
| Erme – Lower Piles |
| Year |
Trout Fry density |
Grade |
Trout Parr density |
Grade |
Salmon Fry density |
Grade |
Salmon Parr density |
Grade |
| 2002 |
15.59 |
C |
15.02 |
B |
3.69 |
E |
0.85 |
E |
| 2003 |
13.93 |
C |
8.47 |
C |
1.09 |
E |
2.73 |
E |
| 2004 |
29.61 |
B |
12.21 |
B |
18.32 |
D |
3.05 |
D |
| 2005 |
30.63 |
B |
12.25 |
B |
16.44 |
D |
6.13 |
C |
| 2006 |
25.97 |
B |
9.74 |
C |
8.99 |
E |
4.25 |
D |
| 2007 |
20.53 |
B |
21.38 |
A |
4.5 |
E |
6.75 |
C |
| 2008 |
11.88 |
C |
4.99 |
D |
0.48 |
E |
3.09 |
D |
| 2009 |
14.20 |
C |
13.74 |
B |
0.93 |
E |
4.19 |
D |
|
| Yealm – Potson’s Wood (SX6027056630) |
| Year |
Trout Fry density |
Grade |
Trout Parr density |
Grade |
Salmon Fry density |
Grade |
Salmon Parr density |
Grade |
| 2002 |
5.8 |
D |
7.1 |
C |
6.2 |
E |
2.1 |
E |
| 2003 |
8.1 |
C |
14.9 |
B |
16.9 |
D |
3.7 |
D |
| 2004 |
5.2 |
D |
12.2 |
B |
27.0 |
C |
5.2 |
C |
| 2005 |
2.1 |
E |
9.8 |
C |
32.0 |
C |
8.5 |
C |
| 2006 |
12.9 |
C |
11 |
C |
39.2 |
C |
8.2 |
C |
| 2007 |
1.0 |
E |
4.1 |
D |
40.6 |
C |
3.7 |
D |
| 2008 |
6.5 |
D |
5.9 |
C |
7.5 |
E |
3.6 |
D |
|
