Fish migrating downstream take quite a risk if their rivers are bordered by industries that use large amount of water for cooling or hydroelectric purposes. Water intakes generally open in the direction of the main current channel of the river, resulting in migrating fish being pulled in. Some die of asphyxiation on the filters, others by a lethal contact with turbine blades. This impact has greatly contributed to the decline of migratory species of fish, such the European eel and the Atlantic salmon, both important as fishery resources. In the particular case of the European eel, threatened worldwide, the cumulative mortality of adults migrating downstream in large rivers towards the sea can exceed 90% due to the succession of industrial water intakes.
This important ecological problem has been legally addressed through the European Water Framework Directive and the recent European Commission for eel protection, underlining the need to reduce this kind of mortality. Various behavioural barriers have been tested to deflect fish away from a water intake by the use of stimuli like light, sounds, electric fields, bubble curtains, with a relative efficiency.
Now, ProFish Technology, a spin-off of the University of Liège (Belgium) proposes a new concept of fish behavioural barriers based on the emission of infrasounds. This technology has been developed by the University of Oslo, Norway (Prof. O. Sand), and was successfully tested by the University of Liège on a nuclear cooling water intake in Belgium. Based on these encouraging results, Dr. Damien Sonny, fish biologist of the University of Liège and now Director of ProFish Technology, has acquired an exclusive licence from the team of Prof. O. Sand in order to propose infrasounds as an efficient behavioural barrier to industries and rivers managers.
Infrasound are acoustic signals characterised by frequencies below 20 Hz, too low for human hearing. Infrasounds are natural alarm signals for fish, and the intensity used by the infrasound fish fence of Profish Technology create literally shake the fish, creating an uncomfortable area that they always avoid, with no habituation. Consequently, this system has revealed in the scientific literature the best efficiency results on the largest number of fish species, as observed during the test on the cooling water intake in Belgium where a reduction of 85% of the fish entrained was observed. An adequate location of the infrasound units will thus induce avoidance trajectories of fish. It is possible to adapt the operation of the system to migration periods of target species, in autumn for the downstream run of the eels, or in spring for the migration of young salmon.
The nuclear power plant of Tihange (Electrabel) in Belgium, that collaborated actively with the University of Liège during the basic research, has shown its interest in the infrasound technology, and by this autumn, several infrasound units will be placed at the mouth of the water intake to keep fish downstream migrating in the main channel of the River Meuse. Electrabel Tihange will be pioneer in the use of infrasound on industrial water intake.
Beside the repulsion technology, ProFish Technology proposes the design and the conception of fish passes, for upstream and downstream migration, addressing solutions to all kind of fish migration problems, with the possibility to use infrasound as a guidance towards fish passes.
Through its technology and services, ProFish technology reconciles industrial activities with responsibility for environmental concerns. Several companies have already showed an interest, and some contacts have been made with Hydroquébec (Québec-Canada), New York Power Authorities (USA), EDF (France) and Shell (Australia).
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