Lakes and Watercourses
Lakes and Watercourses
Lakes and Watercourses
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TABLE 48.<br />
(Contd.)<br />
Proportion of alien species 5<br />
Class<br />
Description<br />
1 No or insignificant deviation 0<br />
2 Slight deviation 0 – 0.01<br />
3 Significant deviation 0.01 – 0.02<br />
4 Large deviation 0.02 – 0.05<br />
5 Very large deviation > 0.05<br />
Overall index 6<br />
Class<br />
Description<br />
1 No or insignificant deviation < 2.8<br />
2 Slight deviation 2.8 – 3.3<br />
3 Significant deviation 3.3 – 4.5<br />
4 Large deviation 4.5 – 4.9<br />
5 Very large deviation ≥ 4.9<br />
1 Only fish species native to Sweden are included. The reference value (J) is calculated as follows:<br />
J = 1.19 + 0.71 · [Log 10 (Width)] + 0.419 · [Catchment] + 0.142 · [Lake percentage]<br />
– 0.0019 · [Height above sea level] using the class values below for the catchment areas <strong>and</strong><br />
percentage of lakes. Width <strong>and</strong> height are expressed in metres.<br />
Class Catchment Percentage of catchment upstream comprising lakes<br />
1 < 10 km 2 10 %<br />
The deviation is then calculated as the ratio between the recorded value <strong>and</strong> the reference value.<br />
2 Biomass <strong>and</strong> number are expressed per 100 m 2 .<br />
3 At localities where salmonids occur (char, grayling, trout or salmon), a calculation of the number<br />
these four species having yearlings (recruitment) is ascertained. The number of breeding species<br />
is divided by the number of species of salmonids.<br />
4 Presence of species <strong>and</strong> stages sensitive to acidification.<br />
a) High density of yearling trout <strong>and</strong>/or presence of yearling salmon, roach or minnow.<br />
b) Presence of cyprinids, gudgeon (Cottus gobio), stone loach (Noemacheilus barbatulus), spined<br />
loach, Wels (Siluris glanis) or crayfish <strong>and</strong>/or occurrence of yearling burbot, grayling or char.<br />
c) Presence of bullhead, ruffe, burbot, grayling, char, whitefish, vendace, salmon or eel (Anguilla<br />
anguilla) <strong>and</strong>/or presence of yearling trout or perch.<br />
d) Only fish present are perch, pike or mature trout (older than yearlings).<br />
e) Absence of species.<br />
5 Calculated as percentage by weight of fish species not native to Sweden out of the total catch.<br />
6 The overall assessment of deviation is obtained by calculating the mean class value for all parameters<br />
included (maximum 7 parameters).<br />
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