The two-tonne fish swim in with the heatwave

Giant ocean sunfish have been spotted in UK waters off the south-western tip of Cornwall during an aerial survey of marine life.

A total of 19 of the species - the world's largest bony fish which can weigh more than two tonnes - were counted in two hours.

The survey was carried out by researchers from the University of Exeter's school of biosciences, the Marine Conservation Society and Cornwall Wildlife Trust.

The sunfish - their name refers to their habit of lying at the sea surface on their side as if sunbathing - feed mainly on jellyfish.

They are generally thought to be a warm-water species, but in recent years sunfish have been recorded more frequently in UK waters during the summer and are thought to be an indication of the rising temperatures of UK seas.

"This sudden influx of these beautiful, giant fish was a fantastic surprise," said Dr Brendan Godley senior lecturer at the University of Exeter Cornwall Campus.

"We only spotted the sunfish lying on their side at the surface so there may have been more below the waves.

"This is the first time we have spotted them during our surveys and we think they have arrived here in order to take advantage of anticipated jellyfish blooms as the summer sea temperatures rise."

The same survey - carried out last Thursday - also detected basking sharks, porpoises, seals and jellyfish.

Previous surveys have also recorded bottlenose and common dolphins.