Large ornamental fish, such as this koi which was caught in the Upper Mississippi River in 2006, have been illegally released into the wild by owners who no longer want to care for them. Photo credit: J. Morrison.

Reports of large, exotic fish caught by anglers, commercial fishers, and fishery resource managers in public waters have become all too common across the country in recent years. 

The causes for most of these unexpected and environmentally troubling landings are hobbyists (aquarium owners and water gardeners) who can no longer care for their ornamental fish (e.g., pacu, koi) that grew to an unmanageable size and were purposely released into nearby surface waters as a quick solution.  Pet owners should know that the release of these fish (and the disease pathogens that may infect them) could adversely impact native fishes with serious consequences for sport and commercial fisheries. 

Faced with a dilemma like this, fish hobbyists need to learn of approved alternatives to the illegal abandonment of their aquatic pets in the wild.  One such option, now offered in western Wisconsin, is a government-business partnership that was established in 2006 by the La Crosse National Fish and Wildlife Conservation Office.  Several pet retailers in this region (that do not offer these frequently problematic fish for sale) have agreed to accept and quarantine large, unwanted pet fish from owners who can no longer care for them. 

Because there is virtually no market for these businesses to re-sell such large fish to other pet owners, the La Crosse NFWCO will accept custody of these unwanted fish and humanely euthanize them at no cost.

Due to this unique partnership with local businesses, the Marineland Pet Center in Onalaska recently accepted seven large hobby fish from owners who no longer wanted to care for them.  On December 4, 2007, the La Crosse NFWCO took possession of these native South American species which included four black-fin sharks (Arius seemanni; 10-11 inches in length) and three oscars (Astronotus ocellatus; 11-12 inches in length). 

The fish were humanely euthanized with Finquel (MS-222), a U.S. Food and Drug Administration-approved anesthetic for cold-blooded vertebrates, and cryopreserved later that day. 

With the receipt of these fish, this partnership program has helped to prevent the potential release of 10 large, unwanted pet fish into Coulee Region surface waters during 2007.  After preparation by a taxidermist, some of these specimens will become part of an informative display used during La Crosse NFWCO outreach activities to increase public awareness of potentially problematic pet fish and acceptable alternatives to the release of these animals in the wild.