Fish in the River Cherwell will be counted and measured using an electric shock treatment as part of a wildlife revamp at Spiceball Park.
The survey, which will take place on August 25, is the first phase of habitat improvements for fish, birds and river plants.
It is being done so before-and-after figures can be obtained to gauge the success of the project with another count taking place in a year.
Nature conservationists Vaughan Lewis will use electric shock treatment to stun fish in a 75-yard stretch of the river.
He will then collect them in nets, measure and identify them.
The makeover will be overseen by the Berks, Bucks & Oxon Wildlife Trust – in conjunction with the park’s owners, Banbury Town Council.
Colin Clarke, chairman of the council’s general services committee, said: “This is an important project and the survey will reveal a great deal about the condition of the river before the improvement work goes ahead.”
Judith Hartley, who works for the trust, said: “The count will take place between the bridges in Spiceball Park and the riverside will remain open to the public.
“We are not expecting a large crowd, but anyone interested can come and watch.”