Problems Unfortunately, a number of exotic fishes are released
into the wild each year. Hobbyists may not be able to take their fish with them
when they move, or they simply may lose interest in maintaining an aquarium. Fish
may also be released if they outgrow th e aquarium or if they appear to be in
poor health. Whatever the reason, releasing exotic fish into local waters is not
a good idea. For one thing, it may be illegal. But there are sound biological
Released fish will be physiologically stressed upon
introduction to a different environment.
They will be susceptible to
parasites and diseases.
They might be attacked by native predators, such
as larger fish, fish-eating birds, or water snakes.
If exotic fish survive and reproduce, they are difficult, if not impossible
to control or eradicate.
They may cause changes in the existing aquatic
community through competition with native species or predation on them, as well
as through overcrowding or aggressive behavior.
They may infect native
fish with exotic parasites or diseases.
An exotic may also affect the
genetics of native species by hybridizing with them.
Sole species may
pose a physical or public health threat, such as piranhas and freshwater stingrays.
Problems Currently, at least 185 different species of exotic fishes
have been caught in open waters of the United States, and 75 of these are known
to have established breeding populations. Over half of these introductions are
due to the release or escape of aquarium fishes. Because many of these fishes
are native to tropical regions of the world, their thermal requirements usually
prevent them from surviving in temperate areas. In the U.S., therefore, most introduced
fishes have become established in Florida, Texas, and the Southwest. Examples
include a number of cichlid, such as the oscar, Jack Dempsey, jewelfish, convict
cichlid, Midas cichlid, and spotted tilapia; and livebearers, such as swordtails,
platies and mollies, and armored catfishes. The goldfish, a native of China, is
one of the few examples of a temperate aquarium species that is established throughout
to Release Instead of subjecting the fish to potentially harmful environmental
conditions or risking potential ecological problems by releasing it, there are
alternative means for disposing of unwanted pet fish:
Return it to
a local pet shop for resale or trade.
Give it to another hobbyist, an
aquarium in a professional office, a museum, or to a public aquarium or zoological
Donate it to a public institution, such as a school, nursing home,
hospital, or prison.
If these options are not available, a veterinarian or fishery biologist can euthanize
it (put it to sleep) with anesthetic. You can also do this at home by placing
the fish in a container of water and putting it into the freezer. Because cold
temperature is a natural anesthetic to tropical fishes, this is considered a very
humane method of euthanasia. A pet shop also may be able to assist you if euthanasia
is the option you choose. An excellent discussion of fish euthanasia was published
in the September 1988 issue of Tropical Fish Hobbyist. This magazine is available
through pet shops or at your local library.
If you must give up your pet fish,
please consider its well-being and its potential impact on the environment. Do
not release it into a natural body of water.