Don’t Release Fish Into the Wild!

03 Mar, 2009

Pterygoplichthys disjunctivus - Image by Jan Hoover, US Army Core of Engineers

Pterygoplichthys disjunctivus – Image by Jan Hoover, US Army Core of Engineers

The government of South Africa is considering legislation aimed at controlling invasive organisms, including fish.  Despite appeals to aquarium owners not to release “plecostomus” catfishes into natural waters, specimens of Pterygoplichthys disjunctivus, the vermiculated sailfin pleco, have been collected from South African rivers.  According to a report by John Dawes in the March issue of Pet Product News International, the US Geological Survey is conducting research to determine potential ecological effects of the pleco “invasion.”  Dawes notes the same species has been reported from seven other countries, including the United States.

Ecologists have been begging aquarium hobbyists for years not to release exotic fish into natural waters, but the problem repeatedly crops up.  While we still do not know enough about ecosystem dynamics to predict the long term consequences of exotic species invasions, a prudent approach would be to assume they are not helpful.  All of the weeds that plague my garden, for example, are exotics.  We can assume they have been introduced since the arrival of European colonists.  Therefore, in a couple of centuries natural selection has failed to eliminate them.  Plenty of reports show that non-native species, from the zebra mussel to Asian water milfoil to Indo-Pacific lionfish, are wreaking havoc wherever they have become established.  In the case of the vermiculated sailfin pleco, they could be affecting native fish species or damaging invertebrate habitat (which affects the food chain) or even, as a result of their breeding behavior, contributing to bank erosion.

The point is that the effects of introducing any exotic species into any habitat are unpredictable, typically negative, and of unknown duration.  Perhaps, in a thousand years, the local species will adapt to the invader, or perhaps the invader will fail to thrive in unfamiliar surroundings and eventually die out.  But in the meantime, the entire ecosystem can be adversely affected.

And, as a political matter, introductions of invasive exotics by the aquarium industry are unlikely to win us any supporters.  So, please, never release an unwanted fish into a nearby lake or stream.  Even if the odds of its survival seem small, don’t take unnecessary risks.  Talk to aquarist friends and your local dealer.  Maybe you can find someone to take the fish off your hands.  Or, as a last resort, euthanize the fish.  But don’t release it into the wild.

Related Posts

About the author

John Tullock

John H. Tullock is a zoologist and one of America's leading proponents of environmentally sound aquarium keeping. A native of Tennessee, John received a Master of Science degree from the University of Tennessee in 1976, studying ichthyology under Dr. David Etnier, who is perhaps best known for his discovery of the snail darter. After teaching college-level biology for a number of years, John and a group of partners founded Aquatic Specialists in 1987, which grew to become one of the largest direct-to-consumer national suppliers of marine fishes, invertebrates, and live rock to aquarists. In 1994, he moved on to pursue a career as a writer and consultant to the aquarium trade. He is the author of over a dozen books, including the popular Natural Reef Aquariums. His numerous articles have appeared in every major aquarium publication. An orchid enthusiast, John has also written about his favorite plants. His Growing Hardy Orchids (2006, Timber Press) was named by the American Horticultural Society as one the year’s five best garden books. He is the founder of the American Marinelife Dealers Association, an organization of aquarium-industry businesses that promotes environmentally sustainable practices and education for conservation awareness. He was a member of the steering committee that helped create the Marine Aquarium Council in 1997. John also serves on the board of Conservation Fisheries, a non-profit that operates the only private hatchery in North America that raises endangered and threatened species of native American fish for habitat restoration and species-recovery projects. John is an avid outdoorsman, with a particular fondness for exploring the Cumberland and Appalachian Mountains near his home in Knoxville, Tennessee. John H. Tullock is the author of: Growing Hardy Orchids - Natural Reef Aquariums -

Leave a reply

Receive FREE e-Newsletters from the editors of AMAZONAS Magazine.

Sign up to get interesting news and updates delivered to your inbox.

Thank you! You have successfully subscribed to the AMAZONAS Magazine email newsletter.

Receive FREE e-Newsletters from the editors of CORAL Magazine.

Sign up to get interesting news and updates delivered to your inbox.

Thank you! You have successfully subscribed to the CORAL Magazine e-newsletter.