Fish Deterrent and Protection Using Non-Physical Barriers & Special Intake Screens

With today’s new legislation of 316 (b) regarding the reduction in mortality of juvenile fish, there are numerous ways to increase survivability with proven technology. This paper will discuss two (2) of those methods; a) Fish Guidance and b) Fish Recovery. The first method of “Fish Guidance” utilizes years of research followed by a number of successful and proven installations of “guiding” or deterring fish via the proper combination of stimuli. Fish will respond to certain queues yet over time, seemed too have acclimated and ignored what was previously a nuisance to them. This was primarily due to only one type of stimuli or a set frequency being utilized. The proper combination sound, air and light have been successfully employed to deter populations of fish from a particular destination. The use of a Sound Projection Array (SPA), which utilizes an altering frequency of sound to repel fish and warn them of impending danger causes them to steer away from paths such as circulating water intakes, thus reducing the quantity of fish drawn into the cooling water system. Other methods include a BioAcoustic Fish Fence (BAFF), which utilizes an SPA combined with a bubble curtain, which captures the sound thus increases the dispersion to the surface and can guide migratory fish around an intake structure. Other installation may also use strobe lights to provide a visual queue or warning of the approaching deterrent system. Certain installations require the use of all three to properly guide various species past structures. Levels as high 73-95% deflection have been attained in many installations. The second method of “fish recovery” uses specifically designed cooling water intake traveling screens to recover fish drawn into the intake system and release them virtually unharmed away from the intake. Traveling screens are used to prevent debris from clogging a plants condenser. Fish normally impinged against the mesh and would otherwise find themselves in the debris washed from the screens are now captured in a hydraulically stabilized “fish bucket” which provides both shelter and a quick, safe removal from the screens. The stabilized shape literally draws the fish into the bucket vs. impingement via exhaustion against the mesh. As the screen rotates, low pressure fish sprays remove fish from the screens, placing them into a dedicated fish return trough. Survival rates vary by species but for many installations have been as high as 85-90%.