Thousands of perch, roach and rudd have been moved to a purpose-built lake in East Yorkshire for a scheme that will encourage people to take up angling.
The Environment Agency says it has a duty to develop fisheries
The Environment Agency has donated £10,000 towards the project at Brough to teach people how to fish.
Animal rights campaigners said the agency was promoting a "cruel" sport.
But the agency said it was part of its government brief to encourage new anglers to a sport which has helped to tackle anti-social behaviour.
People for the Ethical Treatment of Animals said angling caused fish severe pain and urged the Environment Agency to spend its money on wildlife conservation instead.
Ethics of fishing
Campaigner Anita Singh said: "Fish are so abused that people are usually shocked when we explain the many different ways that they suffer."
The Environment Agency said it had a duty to maintain, improve and develop fisheries, which included the promotion of angling.
It said its fisheries work was funded by anglers' rod license fees and not by public money.
"The ethics of fishing and the questions of what constitutes pain and whether or not fish can feel it are a matter for Parliament, which defines our duties, and for individuals," a spokeswoman said.