Sensory, behavioural barriers (electricity, light, sound, air-water curtains)
Fish are deterred by a series of measures, including flashing lights, noise, air bubbles and electrical power. This can be used to control fish from dangerous migration routes, such as intake for turbines. The measure initially only works if the fish has alternative migration routes, for example escape routes and safe bypasses. The guiding impact can be improved with attraction measures such as increased water flow to a bypass (repulse and attract). Common for repulsion measures is that they usually only work for parts of migrating fish, that they work less well by flooding and are selective in terms of species and sizes. Fish may also be accustomed to deterrence measures over time, so that they get lower efficiency.
Design varies between the methods and refers to the literature below. The most important deterrence methods are:
- Electric screens (for more information: Fish Protection System (induced drift application))
- Strobe light
- Bubble curtains
- Acoustic deterrence, e.g. BAFF (bio-acoustic fish fence), which is a perforated tube located below the surface that emits sound and compressed air, which will act as a repellent on fish.
Promising results have been obtained with various experimental behavioural screens in laboratories or on test sites. However, not many prototype installations have been evaluated. Furthermore, the technology has not met the expectations and the results obtained in field applications have been much less reliable than those obtained under controlled conditions (EPRI, 1986) (Kynard, et al., 1990), (EPRI, 1994), (Gosset, et al., 1999), (Therrien, et al., 1998) (Travade, et al., 1999), (Larinier, et al., 2002), (Bau, et al., 2008). Furthermore, their scope of application is otherwise limited to low flow velocities (<0.3 m/s).
Care should be taken when using behavioural barriers, especially since manufacturers of these products have a high marketing interest to promote the use of their technology and may deliberately overestimate their effectiveness (Larinier, et al., 2002).
Methods, tools, and devices
Sensory and behavioural barriers like electricity, light, sound and air/water curtains are not efficient used alone and only works for specific species. Correctly choosing and designing the combined mitigation measure (like fine mesh screens) is imperative.
Attraction and repulsion measures are installed in collaboration between fish migration experts and product suppliers.
Such barriers are convenient for designers and users alike because, unlike physical barriers, they require only minimum maintenance and cleaning efforts against blockage.
Assessment of efficiencies can be obtained by survey of fish by telemetry.
Relevant MTDs and test cases
Please note: The TRL varies based on the technology applied. TRL 4 is the highest of these.
|Fish species for the measure||All|
|Does the measure require loss of power production||Operational (requires flow release outside turbine)|
|Recurrence of maintenance||Irregular at events|
|Which life-stage of fish is measure aimed at||-|
|Movements of migration of fish|
|Which physical parameter is addressed||N/A|
|Hydropower type the measure is suitable for||Plant in dam|
|Plant with bypass section|
|Dam height (m) the measure is suitable for||All|
|Section in the regulated system measure is designed for||In dam/power plant|
|River type implemented||Steep gradient (up to 0.4 %)|
|Fairly steep with rocks, boulders (from 0.4 to 0.05 %)|
|Slow flowing, lowland, sandy (less than 0.05 %)|
|Level of certainty in effect||Very uncertain|
|Technology readiness level||TRL 4: technology validated in lab|
|Cost of solution||See cost table|
- Bau, F., et al. 2008. Suivis par radiopistage de la dévalaison de l'anguille argentée sur le Gave de Pau au niveau des ouvrages hydroélectriques d'Artix, Biron, Castetarbes, Baigts et Puyoo (2007-2008). s.l. : Rapport GHAAPE RA.08.06, 2008.
- EPRI. 1986. Assessment of downstream migrant fish protection technology of hydroelectric application. Boston, Massachussetts : Stone and Webster Eng. Corp., 1986. S. 420.
- —. 1994. Research update on fish protection technologies for water intakes. Boston, Massachussetts : Stone and Webster Eng. Corp., 1994. S. 225.
- Gosset, C und Travade, F. 1999. Etude de dispositifs d'aide à la migration de dévalaison des salmonidae: barrières comportementales. 1999.
- Kynard, B und O'Leary, J. 1990. Behavioral guidance of adult American shad using underwater AC electrical and acoustic fields. s.l. : Proceedings of the international symposium on fishways, 1990. S. 131-135.
- Larinier, M., Travade, F. und Porcher, J. P. 2002. Fishways: biological basis, design criteria and monitoring. 2002, S. 208.
- Therrien, J und Verreault, G. 1998. Évaluation d’un dispositif de dévalaison et des populations d’anguilles en migration dans la rivière Rimouski. 1998.
- Travade, F, Gouyou, G und De Faveri, N. 1999. Efficacité d'un exutoire de dévalaison et d'une barrière acoustique pour les smolts de saumons atlantiques (Salmo salar L.) à l'aménagement hydroélectrique de St Cricq sur le gave d'Ossau. 1999.