28/05/2026
Dry, warm weather can negatively impact fisheries by lowering water levels, dissolved oxygen and increasing the risk of disease ☀️🌡️
Being prepared can help protect your fish stocks and fishery. We highly recommend preparing well in advance to reduce the risks of summer weather:
• Think ahead and be prepared. Plan what to do in the event of an incident. Sharing your plans with colleagues, or with angling club members, will ensure they’re aware and prepared to reduce the impacts of incidents at your fishery.
• Be vigilant. Closely monitor water levels and oxygen and look for any signs of fish in distress, e.g. fish gasping at the surface. We recommend visiting the fishery early in the morning when dissolved oxygen levels are at their lowest (this is typically when you’re likely to observe fish in distress) and ideally midday and in the evening.
• There’s a direct relationship between temperature and dissolved oxygen, with higher temperatures resulting in lower dissolved oxygen. This is because oxygen is more soluble in water at lower temperatures. Therefore, recording temperature alongside dissolved oxygen is useful.
• As a rough guide, try to maintain dissolved oxygen levels to at least 50% for coarse fish and 70% for trout. However, it’s important to recognise that all waters are different. To best track the dissolved oxygen 'rhythm' for your fishery, aim to record temperature and dissolved oxygen three times a day and make a note of the readings. Over time, you'll soon recognise what the 'good' and 'bad' levels are for your fishery.
• If you think your fishery may be at risk of low dissolved oxygen (e.g. due to algal growth, low water levels or rising temperatures), be prepared and check that you have access to water pumps, aeration equipment and generators.
• Don’t remove too many plants, as their presence can push up water levels through displacement which can help in drought conditions. Maintaining a balance of aquatic plant growth provides essential dissolved oxygen during the longer, hotter summer months. In some circumstances, maintaining fishable swims may be preferential to clearing vast areas.
• Floating plants such as duckweed can grow prolifically and if left unmanaged, can prevent oxygen from entering the water. Regularly net-off duckweed to allow the exchange of gases at the water surface.
• Consider restricting ground-bait, loose fish feed (pellets etc.) and liquid baits to avoid further lowering water quality.
• Maintain fish welfare. Minimise the use of keep-nets. If a match is planned, consider using multiple weigh-ins to avoid unnecessary stress to fish stocks.
• Avoid stocking fish during warm, dry weather. As water temperatures rise, water holds less oxygen. If stocking is necessary, delay until cooler conditions are restored and oxygen levels are higher.
• Consider reducing your stock densities to avoid problems later. Periodically removing prolific-breeding species such as roach will allow improved growth rates in remaining fish, plus increased resilience to disease and improved water quality. You need authorisation from us to remove fish from your water (other than by rod and line).
• Fish may be more vulnerable to disease during warm weather and when stressed. Please report any suspected disease outbreaks to us immediately.
If you see any fish in distress or suspect a fish disease outbreak, please tell us immediately by calling our National Incident Hotline on 0800 80 70 60.
