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What to do if fish are dying

Environment Agency
June 29 2015

The sight of dead fish is devastating for any fishery manager, club or angler. Taking action at the first sign of dead fish can reduce the number of fish lost and allow the fishery to recover quicker.
What you should do
If you do have fish dying at your fishery there a number of things you need to do immediately:
Stop fishing!
This will reduce the stress levels within the fish population, helping the fish to recover. This will help to lower the total number of fish that may die. It will also protect other fisheries from the potential spread of disease on fishing tackle. Fishing should only start again when fish have stopped dying and all the remaining fish are healthy.
Report it!
Act quickly and report any fish deaths to the Environment Agency immediately on 0800 80 70 60. We will investigate by discussing the problem with you. If a disease outbreak is suspected then we will examine a sample of fish. Our examinations look for what disease is killing the fish. We will also give advice on how to reduce losses and prevent future problems.
Don’t try to rescue the fish!
If they have a disease then they will take it with them and infect other fish elsewhere. The stress of moving them will also make them worse, leading to more deaths.
Never re-stock!
Do not put fish into a fishery with an on-going mortality problem. The new fish will only suffer from the same problems and may bring other diseases with them. It will also increase stress levels in the new and old fish causing more deaths. This will cost you more money.
Why it is a good idea to get your fish checked
Getting the mortality investigated will help you work out what is killing your fish, whether it is related to a disease outbreak, the site management or both. This will help you make improvements to prevent future fish deaths. A full review of the management and conditions in the fishery is therefore essential. It should highlight any factors that would have caused stress to your fish and contributed to the losses, such as:

were there too many fish;

was there a problem with water quality;

was the habitat or water quality unsuitable for the fish population;

was there a risk of disease introduction