'Finding Nemo' pets harm ocean ecology

In Disney's version, the brightly coloured fish escape their aquarium and return to the ocean where they live happily ever after. But in reality, the liberated cast of Finding Nemo could threaten the very survival of some of the most exotic marine life in America.

In Disney's version, the brightly coloured fish escape their aquarium and return to the ocean where they live happily ever after. But in reality, the liberated cast of Finding Nemo could threaten the very survival of some of the most exotic marine life in America.

Tropical fish are being returned to the "wrong" ocean by their owners.

A team at the Florida Keys Marine Sanctuary has discovered a brace of unusual fish that would never normally be found there, including a pair of orbicular batfish, more commonly seen in the Pacific - but popular among aquarium owners. Since 2000 there has been a growing number of sightings by divers and fishermen of the predatory, and highly poisonous, lionfish, along the eastern seaboard from North Carolina to New York.

The US Geological Survey (USGS) has a growing database of sightings and captures of "non-indigenous fish". Off Florida alone, it includes the raccoon butterfly fish, several varieties of the tang and angel fish, and the orangespine unicorn fish. All are popular aquarium choices for their colour and variety.

"It's a Finding Nemo story," Brice Semmens, a marine biologist at the University of Washington in Seattle, told New Scientist magazine.

"Individuals are releasing their pet fish with the best of intentions, but in the wrong ocean. It is a really bad idea." The incoming fish can drastically alter the ecological balance of an area. The lionfish, for example, preys on a range of fish, shrimps and crabs but the Atlantic species have not evolved any strategy against it. "Introduction of the lionfish is an ecological quantum leap for local fishes that have no experience dealing with this voracious predator," said Dr Semmens.

He carried out research to link aquariums with the foreign species because others had blamed their presence on ships emptying their ballast tanks near harbours. He compared statistics of imports to the United States of tropical marine fish with sightings collected by the Reef Environmental Education Foundation (Reef) from 1993 to 2000.

His research showed that the more a species was imported, the greater the likelihood of sightings off the coast; and ships were ruled out because there was no overlap between the natural homes of the fish recorded and shipping routes.

Walter Courtenay, a research fishery biologist with the USGS, suggested that the rise in the number of lionfish off the Florida coast might be due to captains of dive boats introducing them to attract customers - who would have seen the fish in aquariums and on TV, and so be disappointed not to see them when doing their own dive. However, the problem is that the lionfish could be impossible to eradicate once it is established.