A man accused of stealing a shark from a Texas aquarium has said he did so in an attempt to save the creature.

CCTV footage shows a man lifting the 40cm (16in) long horn shark, named Miss Helen, from a petting tank at San Antonio Aquarium, before making off with her in a pushchair.

Anthony Shannon, who has been charged with theft, claims he is an "activist not a criminal" and was compelled to liberate the sea creature over fears her welfare was being endangered by inadequate tank conditions.

But the 38-year-old now faces charges over stealing the fish and taking her to his home, where she was kept in a tank before being tracked down and returned to the aquarium by authorities. Miss Helen was reported to be one of around 25 sharks being kept in large pools at Shannon's home, along with an unknown number of crabs.

The accused told a reporter that the theft was "regretful", but suggested he could justify such behaviour if it was an "emergency" for the sea creature concerned.

"I have a mission," he said. "It's not a mission to steal for profit, it's a mission just to give the fish a better health."

Staff at the San Antonio Aquarium denied accusations that animals were kept in inadequate conditions and said extensive tests were carried out on the water every day.