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Davis, California

Thursday, May 30, 2024

Don’t free your fish

Most animal enthusiasts are familiar with the concept of freeing captive animals. Even bringing up the subject conjures mental images of the morose circus lion longing to roam outside his small cage. It seems that some aquarium owners have taken to this concept — perhaps inspired by the film Finding Nemo — and are emptying their tanks into nearby streams or bays. While well-intended, sending aquarium fish into the wild can prove destructive to the natural ecosystem.

Susan Williams, an evolution and ecology professor with the UC Davis Bodega Marine Laboratory, found that 13 non-native ornamental species of fish were present in California waters. While 13 species may not seem like a lot, Williams’ report to the California Ocean Protection Council cautioned that 69 percent of non-native species artificially introduced have established themselves successfully.

“For example, Caulerpa displaces seagrass, which provides critical habitat for California halibut, lobsters, Dungeness crab and rockfishes,” Williams said.

Caulerpa taxifolia is an invasive species of seaweed used in aquariums. It thrives in temperate waters and has compounds toxic to herbivores, making it very difficult to control. In Crete, the spread of Caulerpa has contributed to a decline in fisheries. The economic costs do not stop there: It cost $6 million to eradicate in Agua Hedionda Lagoon, a coastal marine lagoon located in Carlsbad in San Diego County and in a portion of Huntington Harbour in Orange County. The process also took half a decade after the initial sighting in 2000. It is currently illegal to own, distribute or purchase nine different species of Caulerpa.

Williams continued that one of the most troublesome consequences of introducing non-native species is that they often out-compete native species with high economic value to a region.

“Most introductions probably fail … but if it does reproduce and many people are dumping in the same place then that can actually result in the same species being there and establishing a population,” said Jay Stachowicz, professor of evolution and ecology and member of the state’s Ocean Protection Council. “Most species that have been introduced into any place don’t spread and become a big problem but the issue is that there are few that have become a big problem … once a species has arrived and started to spread, it is very difficult to remove.”

Pterois volitans, more commonly known as the lionfish, is another species of particular concern. The lionfish, native to the east coast of Australia and Indonesia, is most well-known for its poisonous fin rays and its highly aggressive nature. In humans, lionfish venom can cause systemic effects such as extreme pain, nausea, breathing difficulties, convulsions and numbness. In rare cases, stings cause temporary paralysis or even death. It has been sighted in Florida, North Carolina, South Carolina and the Caribbean.

While it has not invaded California waters yet, it is still being imported daily through San Francisco International Airport (SFO), and due to its ability to withstand cooler temperatures, could establish itself further north than the San Francisco Bay.

“It is one of these situations where we could have a very damaging species introduced into the [San Francisco] bay waters,” said Ted Grosholz, a coauthor on the study.

Aside from the lionfish, there are 34 different aquarium species being imported that have the ability to tolerate cooler waters, meaning that if released, they could pose a serious threat to the established food web and ecosystem.

According to Grosholz, the environmental damage from invasive species is like a “killer earthquake.” It has not happened yet, but it is only a matter of time.

“Don’t dump your aquariums,” Williams cautioned. “Take your unwanted organisms back to the vendor or contact your fish and game or wildlife department to learn how to dispose of the organisms properly and humanely.”

NICOLE NOGA can be reached at science@theaggie.org.


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