Some of the UK’s leading experts are warning overstocked commercial waters to ‘act now’ and manage their fish populations better ¬ or expect more casualties under the ice in future winters.
Both fisheries management consultant Dr Bruno Broughton and Environment Agency technical officer Nigel Hewlett urged fishery bosses to adopt a ‘be safe not sorry’ policy after mass fish-kills were revealed at several venues in the North-West as waters thawed out following the big freeze.
Worst affected was Duttons Pond, in Urmston, Manchester, but waters in Liverpool, Leigh and carp syndicates in Shropshire were also hit hard.
Angling Times recently reported how anglers jumped into the freezing water at Duttons to smash the ice with axes, after spotting most of its fish gasping for air on the surface.
But last week it transpired that their efforts had been in vain, with an estimated 600-plus dead carp between 3lb to 20lb having to be scooped from the water and buried in mass graves next to the lake.
And it’s overstocking that is to blame.
“Just breaking the ice isn’t good enough sometimes. If a venue’s overstocked, it’s overstocked and fishery owners shouldn’t bury their heads in sand. If you have too many fish in your fishery, nature will eventually find a way of exposing it, like it has just done over the freeze,” said Bruno.
“Heavily-stocked fisheries are more likely to suffer losses if the water is iced over for a prolonged period. Aside from reducing stress, preventing disease and improving fish growth and feeding, this is another good reason for fishery owners to ensure that they manage stock densities more carefully, especially in shallow waters with lots of organic matter sat on the lakebed,” echoed Nigel.
Locals claim Duttons Pond’s management ignored recommendations from fisheries experts to reduce stocking levels in the pond and, instead, introduced more fish. Anglers like Craig Stubbs, who used to bailiff the venue, were resigned to the stocking policy.
“The committee which runs Duttons are all matchmen with a fish-a-chuck mentality. An expert from the Stoke club netted the water four years ago and said he’d never seen nets of fish so large. In his report he recommended the biomass be reduced. Last year I tried to arrange for the lake to be netted, but the committee wouldn’t have any of it!” said Craig.
Instead, the fishery, which is controlled by Urmston and District Angling Association, stocked 400 ide in October 2009 and manager John Lynch admits that the 1.5-acre venue had too many fish in it.
“The Environment Agency advises a stocking level of 500lb per acre and you can see from this regrettable incident that the lake could not sustain the carp that were lost. As a club, we will learn from this and we’re now looking at using aeration equipment,” said John.
A. A layer of ice covered by snow means that light cannot penetrate, stopping plants from producing oxygen.
B. The more fish in t he lake, the more oxygen they need.
C. Bacteria in the silt also use up oxygen.
D. Plants also produce oxygen, but there are very few at this time of year.
E. The shallower the lake, the faster the water's oxygen will be used by the fish.
F. A continuous ice cap stop oxygen entering the edges of the lake.
G. Imagine a minnow in a water-filled jar. If you screw down the lid, the fish will run out of oxygen eventually. This is the effect that complete ice cover can have on fish in a lake.