Fish Guidance Methods – Keeping Fish Safe
Fish need to be protected from inlets and outfalls. If they gain access into pumping equipment they can be killed and fish stocks can be affected. Critical species most at risk are migratory species such as the European eel and salmon.
Several methods can be used to deter and redirect fish out of harm’s way:
Fish Friendly Pumps
Where possible, fish friendly pumps, such as an Archimedes screw, can be used to avoid the need to screen fish.
Acoustic Fish Deterrents
Underwater speakers project sound which some fish do not like to keep them away.
Graduated field fish barriers can be used for outfalls, but there is still a debate as to their effectiveness.
Constant lighting can be used to illuminate obstacles so fish can see it easier.
Strobe lighting can be used as a deterrent to keep fish away.
These are physical grid barriers that cover the entrance to pipes. They are often combined with deflectors to guide fish to a pass or other safe route. These are the most effective physical barrier, but can be prone to becoming blocked by debris. Moving screens overcome this problem as they are self cleaning.
Rising air create a dense curtain of bubbles to keep fish at bay. These are often used as a temporary measure as bubble curtains can block up over time reducing their effectiveness. However, bubble curtains are not effective for eels.
A fish pass is a man-made construction, which allows fish to move past an obstruction such as a weir.
For example, a simple fish pass may be constructed from brush bristles which the fish can ‘swim’ through, even though it is out of the water.
Commercial and Specialised Diving are a diving framework contractor for the Environment Agency. We can design and install fish deterrent systems and fish passes.
If you have a project that requires our help, please do not hesitate to give us a call on 01202 580007.