Carelessness exposes native species to alien invasion
By Bob Bock
Originally published July 14, 2002
ASMALL Crofton pond is ground zero for a biological invasion that could be
disastrous. Someone dumped into the pond a nasty fish that eats everything
in sight -- fish, frogs and even birds.
The fish, the northern snakehead, can slither over land to other bodies of
water and, unchecked by the predators of its native waters in China, might
cause the extinction of a number of local species.
A Maryland resident dumped two northern snakeheads into the pond more than
two years ago because they no longer were wanted as pets, Department of
Natural Resources police said.
The Sun reported July 3 that Walter Courtenay of the U.S. Geological Survey
may seek a federal ban on importing the snakehead into this country. A ban
is a good idea and would help to protect our aquatic life from the
carelessness of a few people.
But a ban won't solve the larger problem we face.
Along with pollution and habitat loss, alien species -- those that people
transplant from one location to another -- pose a threat to the plants and
animals found naturally in North America. Alien species have caused
environmental disasters everywhere they have been introduced to new homes.
For example, zebra mussels multiply uncontrollably, scouring waters of
microorganisms that feed the young of sport fish.
Another example was available at the Crofton pond.
While trying to net baby snakeheads, I came across some bluespotted sunfish.
These beautiful, delicate creatures don't grow much larger than a silver
dollar. Male bluespots have fluorescent blue spots and build nests to tend
their young. These could be the last surviving bluespots from that pond. If
the snakeheads don't eat them, it's possible they may be eradicated by
attempts to remove the snakeheads.
Anglers can do their part by not moving fish from one body of water to
another. Transplanted largemouth bass have nearly eliminated many fish
native to the desert springs of the United States and pushed others into
A well-meaning act like releasing bait fish after a day's fishing may also
have dire consequences.
Red shiners liberated from bait buckets into the Colorado River carried with
them a parasitic tapeworm. The tapeworm spread to the woundfin, a native
minnow. Not as resistant to the tapeworm as were the shiners, the woundfin
suffered a rapid decline from which they have barely recovered.
Likewise, home aquarists should never release their pets once they grow
tired of them. The Everglades is now full of tropical fish that escaped from
the aquarium trade. The tropical invaders prey on some local species and
compete with others for food and territory.
Whether a species has economic value or is simply worthy of our
appreciation, we'll never gain any benefit from it once it's gone.
But carelessness is something all of us can avoid by never releasing captive
plants and animals into the wild.
Bob Bock is past president and a current board member of the North American
Native Fishes Association. He lives in Silver Spring.
Copyright © 2002, The Baltimore Sun
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