An acoustic fish deterrent uses sound to deter certain groups of fish (i.e. those with well-developed hearing) from the cooling water intakes. Only sprat and herring of the most common fish in the Bristol Channel have good hearing and they are abundant and not commercially fished. The deterrent is less effective for fish with less developed hearing and ineffective for some species.
Evidence provided by the governments marine and freshwater science experts, Cefas, shows that the operation of an acoustic fish deterrent system would have very little effect on protected fish species in the Severn Estuary. The number of fish killed per year could be equated to that of a small fishing vessel.
Installing and maintaining dozens of sound projectors underwater two miles offshore is also dangerous and poses risks to divers that are unacceptable. The Bristol Channel has poor underwater visibility and one of the highest tidal ranges in the world.
As a result of these reasons, we have decided that it would not be appropriate to install an acoustic fish deterrent. Operating a system with negligible benefit for the environment would place a burden on future operators and endanger the lives of workers for decades to come.
Hinkley Point C, like all power stations, needs cooling water to generate electricity. The government’s marine and freshwater science experts, Cefas, predicted the percentage of adult fish stocks taken each year by the power station, just as they would for commercial fishing.
Very large numbers of fish are eaten by other fish, marine birds and porpoises. This natural mortality is typically 10 to 20% of the adult population per year for longer-lived species but 60% or more for shorter-lived shoaling species. Fishing can sustainably take at least 10% to 20% of the adult population every year without affecting the species' ability to reproduce and maintain their population levels. For many species higher levels of fishing are sustainable.
The worst case predicted effect of Hinkley Point C with the planned two fish protection measures in place varies by species, from a maximum of 0.4% to less than 0.02% per year. To put this into context, the total amount of fish estimated to be killed by the operation of HPC without the AFD system has been predicted by Cefas to be around 56 tonnes in a year - about the same as would be caught by one small fishing vessel.
Cefas concluded the predicted levels would have no effect on the sustainability of each species nor on the predators that rely on the fish to survive.
No - the total amount of fish estimated to be killed by the operation of HPC without the AFD system has been predicted by Cefas to be around 56 tonnes in a year - about the same as the annual catch of one small fishing vessel.
Cefas concluded that this level is limited when compared to natural mortality and fishing. The predicted levels will have no effect on the sustainability of each species nor on the predators that rely on the fish to survive.
All power station cooling systems using river or sea water have an impact on fish. Even with measures to protect fish, not all will survive the passage through the cooling tunnels. The fish return system is effective for more robust species.
The total amount of fish taken will be around 56 tonnes compared with 650,000 tonnes commercially fished in the UK each year by over 6,000 boats. So our impact will be equivalent to about a small trawler's catch per year.
Many power stations have taken cooling water from the Bristol Channel in the past with no detrimental impact on fish populations. Hinkley Point C will be the first to include any fish protection measures at all.
Some power stations have experimented with the use of acoustic fish deterrent systems in the past but there has been no use of long-term permanent systems.
It was regarded as emerging best practice when the original plans for the power station were drafted. Now that more detailed design work has been undertaken, Hinkley Point C has concluded that the deterrent does not provide significant environmental benefit and that its installation and on-going maintenance poses unacceptable safety risks to divers and workers.
Hinkley Point C will be the first power station in the Bristol Channel to have fish protection measures installed. The cooling water system includes low velocity side entry water intakes designed to minimise the number of fish taken into the system and a fish return system.
The Hinkley Point C cooling water intake system will take seawater direct from Bristol Channel before returning that same water back into the sea. Water will be taken through intake heads and tunnels 3.3km from the shore at a depth of 20m below the seabed. Once at the shore the water will go through a filtration system of coarse and fine mesh screens in a cooling water pumphouse. Fish will be returned to the sea via a fish return system.
We are now working with the Environment Agency, Natural England and Natural Resources Wales to develop a proportionate and robust compensation package to mitigate any impact of the removal of the acoustic fish deterrent system.
Typically, there are between seven and ten species that make up 95% of the fish found around Hinkley Point: European sprat, herring, whiting, sole, cod, thin-lipped grey mullet, flounder and 5 bearded rockling. Of these species only sprat and herring have good hearing, the others have average to poor hearing and are therefore less likely to respond to sound deterrents. Twenty fish species were included in the comprehensive assessment undertaken by Cefas.
These migratory species do use the Severn Estuary but primarily use the main channel of the estuary they also swim near to the surface. They are not expected to be affected in any significant numbers as the water intake structuresare about 10km from the main channel and are near the bottom.