Severn Trent has been ordered to pay £480,000 for a pollution incident.
According to the Environment Agency, raw sewage leaked into a farmer’s field and a pond in a private fishery at Bramley, Rotherham last year.
It added Severn Trent had been warned on two previous occasions for similar incidents at the same location.
The water company’s pipeline that transported raw sewage to a treatment plant ruptured, which led to four pollution incidents within a year.
That directly contributed to fish deaths, the Environment Agency said.
The water company must also pay more than £13,600 in costs as well as a victim surcharge of £120.
An Environment Agency officer involved with the investigation added: “We were particularly concerned that after two formal warnings from the Environment Agency about sewage leaking into fields and watercourses the third rupture was undetected by Severn Trent Water Ltd and there was then yet another incident in the same location.
“This is one of the largest fines ever to be imposed on a water company and I hope it sends a strong message that it is far more cost effective to avoid these incidents as we will continue to take companies and individuals to task where they ignore their responsibilities.”