A wooden stick is attached to make the lollies easy to grip

The lollies, which contain a mixture of mackerel, trout and squid, are being provided for otters at Portsmouth's Blue Reef Aquarium.

Keeper Mat Clarke says they serve a double purpose of keeping the otters cool on sunny days and encouraging them to work harder for their food.

The fishy treats are frozen into blocks of ice and have a large wooden stick attached to make it easier for the otters to grip.

Ice-lollies provide an interesting and unusual challenge for them during the summer Keeper Mat Clarke

Mr Clarke said: "We wanted to create a way of feeding them that meant they weren't simply sitting around waiting for the food to arrive - the ice means they have to use their natural instincts just as they would in the wild to get to the food inside.

"We've added the sticks as it gives them a non-slippy surface to hold onto while they're wrestling with the lollies in their pool.

"Otters are intelligent, inquisitive animals.

"We're always trying to introduce new things to keep them stimulated and the fishy ice-lollies provide an interesting and unusual challenge for them during the summer," he said.