The effects of exposure of rainbow trout eggs/larvae to a static magnetic field or 50 Hz magnetic field on the development should be investigated.
The magnetic field strengths in this experiment corresponded to the maximum measured values in the vicinity of AC and DC underwater cables.
Rainbow trout eyed eggs (Oncorhynchus mykiss) (about 4 weeks old) were divided into the following groups: 1) exposure to the static magnetic field, 2) exposure to a 50 Hz magnetic field.
Moreover, there was a separate control group for each exposure group.
After 6, 11, 16 and 21 days ca. 40 larvae and on day 24 ca. 100 larvae were removed from group 1 and the corresponding control group, preserved in alcohol and examined.
After 5, 10, 14 and 21 days ca. 40 larvae and on day 25 ca. 100 larvae were removed from group 2 and the corresponding control group, preserved in alcohol and examined.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
Exposure duration:
for 36 days (from eyed egg stage to approximately 26 days post hatching)
|
|
|
Exposure 2:
50 Hz
Exposure duration:
for 36 days (from eyed egg stage to approximately 26 days post hatching)
|
|
| Frequency | |
|---|---|
| Type | |
| Exposure duration | for 36 days (from eyed egg stage to approximately 26 days post hatching) |
| Exposure source | |
|---|---|
| Chamber | eggs on perforated metal plates in glass tanks (25 L) |
| Additional info | glass tanks were placed in coils; generators produced stable, uniform field throughout the volumes of the tanks; natural photoperiod was applied (12 h day/12 h night), water temperature was maintained at 9°C |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 10 mT | - | measured | - | - |
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | for 36 days (from eyed egg stage to approximately 26 days post hatching) |
| Exposure source |
|
|---|
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1 mT | - | measured | - | - |
From day 14, the yolk-sac absorption was significantly accelerated in both exposure groups compared to the respective control groups. Further observations, which were however not directly associated with exposure to a magnetic field, showed that, in general, an early yolk-sac absorption may be associated with delayed feeding and growth.
All other parameters did not show any significant differences between the exposure groups and the control groups.
The authors conclude that exposure of rainbow trout eggs/larvae to a static magnetic field or 50 Hz magnetic field could accelerate yolk-sac absorption, which in turn could have a negative effect on subsequent growth.
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