Britain's current Arctic freeze-up could lead to an explosion in the number of fish deaths in stillwater fisheries, according to The Professional Coarse Fisheries Association which is advising its members and others responsible for running fisheries to open ice-free holes in lakes and ponds to ensure fish survive the freezing conditions.
PCFA Chairman Trevor Passmore, who runs Passies Ponds Fishery in Lancing, West Sussex, said: "A continuous layer of ice over a stillwater fishery prevents oxygen from entering and waste gases from escaping. Although fish are adapted to survive such conditions for short periods, prolonged ice cover can cause eventual deoxygenation and the subsequent death of fish beneath the ice."
With some lakes having been iced-over for three weeks, and the thickness of the ice increasing daily, the PCFA believes it is inevitable that some unprotected fisheries will succumb to this 'winter kill'.
Most vulnerable are shallow lakes and pools which support large populations of fish and have deep layers of silt or other organic matter on the bed. In these waters, deoxygenation is made worse by a covering with snow which reduces light penetration into the water and prevents even modest oxygen generation through photosynthesis by aquatic plants.
"Where stillwater fisheries have completely iced over, the Association's advice is to create one or more holes in the ice and, if possible, to break any fresh ice on a daily basis. Often, this will necessitate the use of some form of ice-breaker, although - if present - floating aerators or water fountains can achieve the same effect", said Trevor.
He added: "Clearly, fishery owners and staff should take great care when breaking ice, with the work being carried out from the bank only. No-one should venture onto the ice itself."
Despite fears that the shock waves caused by ice-breaking might damage fish, this is not borne out by the experience of fishery owners and fish farmers - especially in mainland Europe - where such action is necessary every winter.