An increase in poaching and extreme weather conditions have pushed fish stocks in British lakes to the point of collapse, an anglers' group has said.
There are claims fishing rules are not properly enforced
Spawning conditions have been hit by two years of extreme weather, the National Association of Fisheries and Angling Consultatives (NAFC) said.
Members of the NAFC have also reported poaching of larger fish from lakes.
And Parliamentary angling spokesman Martin Salter MP claims some eastern European migrants take fish to eat.
The Reading MP said: "Poles and eastern Europeans, in particular, have been seen and occasionally caught removing all species of coarse fish, roach, bream and perch."
BBC correspondent Niki Cardwell says the problem is partly cultural with eastern European immigrants - for whom carp is a delicacy - taking fish from lakes.
They do not realise that it is unacceptable to eat the fish they catch, she says, adding that poachers have been seen patrolling lakes.
Mr Salter says the problem is getting worse but that the legal framework is simply not strong enough to cope with the problem.
"For example, in the Thames region it is legal, even though it's not in our culture, it is legal to take two fish of any size," he said.
"In some other regions you can take as many fish as you like, but there are certain size limits. And these things are simply not enforced."
One lake in Northampton has been forced to close because the problem has become so bad.
And the NAFC warns others could suffer the same fate.
The organisation's representative for the Anglian region, Steve Hellen, said fish were normally fairly comfortable within their own environment.
"But if you introduce extreme elements into that environment, such as we had with very high water levels, fish can become displaced from the normal area within a river, for instance, that they live in.
"And because of man made structures such as weirs and sluices and things those fish may never be able to return to their normal resident area."
Freshwater fish in the UK have been hit by the extreme and prolonged heat of 2006 followed by floods in 2007. Both disrupted spawning and deprived fry from the right conditions to grow.