There is an increased awareness of the impact of water abstraction on aquatic life and this is reflected by legislation in the USA and, increasingly in Europe, requiring abstractors of water to undertake measures to reduce the “impingement” and “entrapment” of aquatic species. Ovivo’s Bio Acoustic Fish Fence (BAFF) fish guidance system is designed to meet legislative requirements and the increasing demands of best environmental practice.
Ovivo’s Bio Acoustic Fish Fence (BAFF) uses a combination of sensory stimuli that produces a linear barrier to guide fish away from the point of abstraction to an exit or bywash. The sensory stimulus is a combination of customised sound signals, directional strobe lighting and an air bubble curtain.
BAFF are commonly used on rivers/lakes to guide the fish to a point downstream of the abstraction point or on hydropower headraces to divert the fish to the bywash.
BAFF have recently been subject to extensive trials in the USA for the diversion of Chinook Salmon smolt in a river system feeding cooling water to a power plant.
Another area of application, unrelated to water abstraction, is for the control of migration of invasive fish species.
The BAFF uses a linear curtain of air bubbles combined with underwater generated sound and intense flashing lights. The sound is encapsulated within the bubble curtain which also reflects and scatters the light. This results in a distinct, highly localised line of sound and light which the fish are reluctant to cross and provides precise directional control.
The acoustic field produced is a characteristic of the BAFF system design and not the local environment therefore, unlike Sound Projector Arrays, acoustic modeling is not necessary. However, since the position of the bubble sheet is strongly influenced by water flows, a good understanding of the water course hydraulics is especially important for BAFF systems.