Abstract
The aim of this study was to determine the effects of artificial magnetic fields on the behaviour of rainbow trout (Oncorhynchus mykiss) larvae. Individuals (from the eyed egg stage) were exposed to a static magnetic field (SMF) of 10 mT or a low-frequency alternating (electromagnetic) field (EMF) of 1 mT, whereas larvae in the control treatment were reared under a natural geomagnetic field (GMF). After 40 days exposure, larvae were tested for 46 h for their attraction to or avoidance of magnetic fields. None of the groups of larvae avoided either the static or alternating field. By contrast, a mean of 54–60% of individuals was recorded in magnetic fields. Moreover, larvae exposed to SMF or EMF were more attracted to their respective magnetic field than individuals reared under a natural GMF. In addition, no stress response (i.e. a change in the oxygen consumption rate) was recorded for O. mykiss larvae exposed to magnetic fields. These results suggest, for the first time, that early life stages of rainbow trout can detect and are attracted to artificial magnetic fields of a magnitude recorded in the vicinity of submarine cables, with no visible signs of stress (i.e. increased oxygen consumption).