Acoustic fish deterrents (AFDs) have become the most effective way to guide and deter fish from estuarine cooling water intakes and have recently been scrutinised by the UK Government in a public inquiry, and an advisory group for the Welsh Government.

Fish Guidance Systems’ (FGS’s) complex proprietary sound signals are tailored with frequencies that maximise the range of species that can be deterred by the AFD.

This not only helps sustain populations, but also prevents disruption to facilities such as power stations where physical screens are provided primarily to filter out weeds and other debris. Even where fish recovery and return systems are provided to put fish back to sea, only the more robust species are likely to survive.

The majority of fish drawn in by coastal power stations are fragile species that only survive if they can be diverted from the water intake heads. In the case of Hinkley Point C, AFDs are an aspect of the Secretary of State’s Development Consent Order (DCO) and the Environment Agency stated there is “high dependency on the proposed mitigation systems”, which include AFDs.

Meeting the Requirements of the DCO

Meeting the Requirements of the DCO

FGS has installed more than 120 sound-based behavioural systems over the course of 28 years. The company is committed to developing new technology that helps conserve fish stocks and prevent damage to plant and facilities.

The DCO requires an AFD to be used at Hinkley Point C in combination with a low velocity side entry (LVSE) intake and a fish recovery and return system.

The LVSE is installed with openings perpendicular to the tidal flow, to discourage fish from entering the pipes of the take. Low design water velocities are intended to help even very small fish to escape entrainment.

The strong tides in the Severn Estuary transport an exceptionally high silt burden, giving zero visibility for fish under most conditions. Without the warning signal provided by the AFD, approaching fish may not be able to detect and avoid the intakes until it is too late.

“The use of an AFD in combination with a low velocity intake is intended to deflect the more fragile hearing-sensitive species that are unable to survive passage through the tunnels and water channels, or handling by the cooling water screens.” Dr Andrew Turnpenny, Fisheries Scientist and Co-founder of FGS

Learn more about the risks to fish at Hinkley Point C

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