Council wildlife rangers are urging anglers to ensure they take home discarded lines and hooks when fishing on local waters.
They issued a strong warning after two swans became entangled requiring emergency treatment.
The two cygnets had to be rescued from Taylor Park lake after suffering injuries caused by fishing hooks and pike fishing trace wire.
One was taken to a St Helens based vet where it was treated before being released back onto the lake the following day.
The second had to be transferred to the RSPCA’s Stapeley Grange Wildlife Centre for surgery.
St Helens Council’s Cabinet Member for Environment and Neighbourhoods, Councillor Seve Gomez-Aspron, said: “Most anglers take a responsible attitude, but there are a few who – through their own negligence – create real hazards for our local wildlife.
“Members of the public and our rangers have been very upset by these two incidents.
“The two resident adult swans at Taylor Park had their cygnets at the end of May – successfully raising five young, which is a fantastic achievement, so we’re asking everyone to help us look after them.”
Naturalists confirm that fishing tackle related injuries are the biggest single cause of swan rescues, now running at more than 3,000 tackle related incidents a year.
The annual cost to the voluntary swan rescue groups (an estimated 1148 of the rescues), excluding labour is estimated to be £94,940 rising to an estimated £202,863 if data for RSPCA rescues is included.