Corby Council has banned fishing at the boating lake as they investigate the reasons why their fish are showing signs of distress.
A statement from the council said that there would be no fishing for at least the next two weeks while their officers work with the Environment Agency and Department for Environment, Food and Rural Affairs (Defra) to undertake tests are to identify the cause.
A spokesman said: “The council understands this is disappointing and apologises to those wishing to fish, but hope that everyone will appreciate and understand why this decision has had to be made.
We will of course endeavour to keep members of the public updated as to when fishing will be permitted.”
The lake at Cottingham Road is a popular spot for fishermen.
In February 2013 anglers said they had spotted an otter at hte lake which was responsible for a large number of carp being killed.
Later that year, the lake was restocked with 5,000 fish for the first time in several years.