An Alien Invasion Hurts Fish and Wildlife

Reprinted from my March 13, 2005 column in the Morgantown Dominion Post     

When the Northern Snakehead fish found it’s way into the Potomac River watershed, many aquatic biologists were concerned, and rightly so. This Asian invader will do tremendous damage to our native fish and aquatic ecosystems. I know. Some have stated that this is no different than carp or other exotic invaders of the past.

Truth is though, that carp and the like have caused billions in damage to natural ecosystems. And while the snakehead is bad, in recent years the list of troublesome and downright nasty invaders is growing rapidly in the United States. None will be beneficial. All will cost millions or more. All will have very negative effects on our natural aquatic ecosystems. Here are some recent examples.

The black carp from Asia has just been found in the Mississippi River. Several were caught in the river in 2004, probably releases from someone’s home aquarium or a private fish pond. They’ve been used by fish farmers to keep their ponds free from algae and other organisms. And as long as they stayed in those farm ponds, they didn’t present a problem. In the Mississippi River, it will be a different story. These critters can grow to 70 pounds, and live 15 years in the wild. They eat shellfish in huge amounts, further endangering mussels in the river that are already in low numbers. They also carry parasites that infect catfish. Not good. Supposedly the ones in farm ponds were sterile and could not reproduce. Whether that is the case with those now in the Mississippi is not known.

There are three other carp that have recently appeared in the Mississippi. The one that has gotten the most attention is the silver carp, because of it’s propensity for jumping out of the water when a boat passes. Often they will jump into boats and human injuries have occurred.

How about the Cuban frog invading Georgia? This tree frog was first found in the Florida Keys eighty years ago, but in recent years they have spread rapidly and now breed in Georgia. These frogs grow to over 5 inches long and eat native frogs and fish. Officials in Georgia are asking any citizen who finds these to report it immediately so they can stop the spread.

Then there is the New Zealand mud snail, recently found in a Colorado stream near Boulder. Formerly the closest they were found was in Utah. Biologists in Colorado are very concerned about this exotic invader because they are especially bad for trout streams. They have not been found in West Virginia.

One of the most famous aquatic invaders is the Zebra mussel. Of special concern are their impact on the commercial and sport fisheries of the Great Lakes. One biologist commented that this mussel has made large expanses of the Great Lakes a biological desert.

Great Lakes aquatic biologists are concerned about a number of exotic invaders. So much so that a $9 million electrical barrier is being constructed in the Chicago Sanitary and Ship Canal that connects the Great Lakes with the Mississippi River. They hope to stop the invasion of the above-mentioned carp, plus a ton of other exotic fish and aquatic organisms including the round goby, the tubenose goby, the ruffe, spiny waterfleas and the quagga mussel. I know. I’ve never heard of most of these species either. But all are extremely damaging to native fish and aquatic organisms and the sport and commercial fishing industry is worth over $4 billion a year in the Great Lakes.

Concern for the Great Lakes aquatic ecosystem is well founded. The four species that make up over 99 percent of the food web in Lake Michigan (those species are the spineless scud, the fingernail clam, the opossum shrimp and various worms) are declining rapidly. That’s what happens when foreign invaders take hold of an aquatic system. Slowly but surely your entire system changes, with major losses of native, fishable, economically important, species of fish.

Local fisheries biologist Frank Jernejcic, discussed these alien invaders in a recent West Virginia Wildlife magazine article. He noted that the Zebra mussel has been extremely costly. For example, it negatively impacts water quality to the extent that industries that use water spend $2 billion a year to remove these mussels from their intake and discharge pipes. Guess who ends up paying for that? Though this mussel is found in the Ohio, it hasn’t gotten into our West Virginia lakes to date.

Frank also mentioned the largemouth bass virus. In 2003 the DNR received legislative authority to regulate fish stocking in public waters, mainly because of this virus.

There are others, but this gives you some idea of the problem. The world is getting to be a smaller place. We travel more by boat, by motor homes, by various means, all of which accelerate the relocation of exotics into the United States. Throw in those who dump aquatic pets into local streams, ponds, lakes, and rivers and the problem accelerates all that much more.

Not all exotics have been bad. Take the brown trout for example. But most have been very harmful to native organisms and the ones mentioned above are no different. Because of these exotics there are species of native aquatic organisms that your children will never get to see. Sad but true.

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Dr. David Samuel