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Flushing Nemo? Pet fish pose ocean threat

Christian Mehlfuehrer / UC Davis

The highly invasive lionfish is easily available through aquarium and internet sales and represents a potential threat for California waters, according to a new report.

By John Roach, NBC News Digital

Exotic and colorful aquarium fish, such as those made famous by the Disney film "Finding Nemo," are escaping to the open ocean in real life and disrupting marine ecosystems, according to a new report on the spread of invasive species.

More than 11 million non-native aquarium fish and plants — from tropical fish to seaweed and snails, representing 102 species — are imported annually through the California ports of Los Angeles and San Francisco, the report found

Of those, 13 species have been introduced to California marine waters, most likely because they were released from aquariums. More than two thirds successfully made a home for themselves in California. 

The number of introduced invasive aquarium species is relatively low compared to those released via other means, such as ballast water released from ship hulls, but aquarium fish are grown to be hardy and robust, which makes them highly successful when they reach foreign waters.

"The aquarium trade species tend to be really bad actors," Susan Williams, a professor of evolution and ecology at the University of California at Davis, told NBC News. "We believe that that is in part due to the fact that they have to be so hardy to be able to survive the trade."

Williams is the lead author of the new report, one of six on the various ways marine invasive species are spread. It was prepared for the California Ocean Protection Council, a government agency. The results, she said, can be generalized to the rest of the world.

The problem of aquarium fish in marine ecosystems has been studied for several years, including work done more than a decade ago by Williams. What’s new here is that the researchers, for the first time, were able to examine data from U.S. Fish and Wildlife inspections, not just what was reported.

The data, in turn, will allow robust comparisons across the other ways invasive species are spread, such as ships and fish farms, and inform agencies on how best to combat the problem.

The new report focused on the killer algae Caulerpa and predatory lionfish, two well-known trouble makers in the aquarium trade. The algae, for example, infected two lagoons in Southern California in 2000 and cost $6 million to eradicate.

Lionfish were introduced to Florida in 1999 and spread throughout the Caribbean and up the East Coast by 2010. They are not yet in California waters, but are able to withstand cooler temperatures and if introduced could establish themselves in San Francisco bay, and further north as waters continue to warm.

"Lionfish are voracious predators in their native habitats, and in their invaded habitat any predator is a potential threat to the native ecosystem," Williams said.

Other aquarium trade species of particular concern include the ever popular green chromis, a damselfish that is being imported through California in large numbers. Even though they are not predators, damselfish are aggressive toward other fish, Williams said.

Preventing the spread of aquarium fish "is not rocket science," she said. Simple measures such as passing out brochures with proper disposal instructions at pet stores would help. Currently, this is not a widespread practice, she added.

"If people were just aware that they shouldn’t dump their aquariums in any natural waters," she said, "that goes a long way to averting this problem." 

John Roach is a contributing writer for NBC News Digital. To learn more about him, check out his website.