Staff at a council-run public park have told of their anger after fish died when a large piece of foam was dumped in a wildlife pond.
Staff at Summerhill Country Park and Visitor Centre, off Catcote Road, Hartlepool, were shocked to make their discovery.
Several fish and tadpoles died after becoming tangled in the net around the foam, which required five members of staff to remove.
The 100-acre site, run by Hartlepool Borough Council, offers a number of play and leisure facilities, and staff there have hit out at the "selfish" behaviour of those responsible.
Adam Reah, from Summerhill Country Park and Visitor Centre, said: “We work hard to provide a beautiful space for local people to enjoy, and we were really shocked and disappointed that someone felt the need to damage the natural environment like this.
“This type of selfish behaviour doesn’t just affect the wildlife in the pond; it also adversely affects the enjoyment of the park for everyone else in Hartlepool.
“Thankfully, the vast majority of people visiting Summerhill Country Park and Visitor Centre respect the site, and we hope this was an isolated incident.
“It would appear that this incident is not going to have a long-term affect on the pond, but the foam could easily have contained nasty chemicals which could have had a lasting impact on the water quality.
“Summerhill is a unique country park that’s both a local nature reserve and an outdoor activity centre, and there is nothing we prefer more than seeing people using the site in a safe and responsible manner.”