First and foremost, Zebra mussels were inadvertently introduced into the Great Lakes when ships from the Baltic Sea region pumped their ballast waters into the lake. At the time, which was more years ago than i would like to remember, Lake Michigan was a filth pit. The waters near Chicago were gray, underwater visibility was essentially zero, most species of fish were considered inedible, at least those that still existed. Most finfish populations were essentially wiped out by both loss of habitat and commercial exploitation. Yellow perch, which at one time were considered the staple of the Great Lakes commercial fishing industry, were so toxic that the consumption level for children, pregnant women, senior citizens, and those with serious health problems were advised to avoid them altogether. Walleye pretty much didn't exist in Lake Erie anymore, their population so low at the time that catching a legal size walleye in a day of fishing was considered a feat in itself. Brown trout, which is another invasive introduced by state and federal fisheries agencies, were thin, sickly looking, and often full of sores or lesions.
The zebras arrived, the water became clear, aquatic grasses emerged from areas of the lake where there previously was insufficient oxygen to support any form of life, yellow perch and walleye soon took up residence in the submerged aquatic vegetation (SAV), and their populations immediately increased by huge numbers. Lake trout and brown trout sizes and populations also grew rapidly, and their overall health improved as well. EPA tests of the finfish population's toxins, particular those usually found in the fatty tissue just beneath the skin, revealed that previous toxin levels were once again in the safe to consume range. How could this be? Industrial polluters didn't suddenly shut off the discharge pipes into the lakes. There were no less people contributing human waste to the wastewater treatment facilities, and those facilities were just as outdated as they were a decade earlier.
Now, lets look at the spawning grounds. Where do most of the finfish of the Great Lakes spawn? Not in the lake - that's for certain. The vast majority of them spawn in fast flowing tributaries, locations where zebra mussels do not exist. In order for zebra mussels to exist they must colonize on themselves. They require slow-moving bodies of fresh water, lakes, and the mouths of larger rivers. The main reason there has never been a large colony of zebra mussels in the Susquehanna River is because the river moves too fast for them to colonize upon themselves - it's that simple.
If they do make it to the Chesapeake's upper reaches, which is doubtful, their chances of survival are slim to none. Diving ducks love to eat them, and guess what, we have lots of diving ducks that winter at the Susquehanna Flats. Additionally, they really don't tolerate salinity very well, though there have been some studies that claim they could tolerate levels reached as far south as the mouth of the Patapsco River, but it's doubtful. Blue crabs also love to eat them, but pollution and loss of habitat, coupled with overfishing by commercial interests, has just about wiped out the bay's blue crab population.
If you're worried about zebras competing with oysters and clams for plankton, well, first we would have to restore the bay's oyster and clam populations in order to have any competition at all. We have lots of plankton, though - much more than we need. There is more than enough excessive plankton flowing down every tributary to Chesapeake Bay to feed the entire zebra mussel population of the entire world, and still have lots left over for the oysters, clams, mussels, menhaden, bay anchovy, and all other plankton consuming species combined.
So, who are these so-called experts that claim the zebra mussels will destroy the bay's ecology? Most of the ones I've come across were state and federal biologists that were out looking for grants to study the effect of the zebra mussels - not experts by any means. Keep in mind these are the same so-called experts that claim if you give them more and more of your hard-earned dollars they'll clean up the bay. Yeah! Still be believe in the Tooth Fairy, too. The Chesapeake Bay Cleanup Program has been going on for more years that most of the good folks on this forum have been alive. During that time, the bay has increasingly become more and more polluted. Do you REALLY believe the tales these so-called experts have been telling you? Lets get serious.
Zebra mussels did one Hell of a good job of cleaning up some of the most fouled waters in the United States - the Great Lakes. They did it at no expense to the taxpayer, and they did it in less than two decades. If they arrived in Chesapeake Bay, and managed to survive the horrendous pollution, established viable populations, maybe, just maybe, they could cleanse the bay's upper reaches to the point where you wouldn't have to worry about eating finfish, shellfish, and crustaceans. Maybe the beaches of Baltimore, Anne Arundel and Charles, Calvert, Kent, Queen Annes, Talbot, and other counties bordering the bay would be once again open to the public. All those beaches are currently closed because of extremely high levels of fecal-colliform bacteria in the waters.
Lets see now, if the zebras arrived and cleaned the waters, we wouldn't need to be shelling out huge sums of money to fund the Chesapeake Cleanup Program, which is now well over $15-billion and growing. We wouldn't need a Chesapeake Bay Foundation to study the sources of pollution in the bay and educate the school kids about how to keep the bay clean. We wouldn't need to fund the EPA's Chesapeake Bay Division. We wouldn't need much of the Maryland Department of Natural Resources Fisheries Administration, which consists of a bunch of biologists that spend huge sums of money studying when the bay's fisheries collapsed. Those fisheries would likely recover on their own.
The bay's SAVs, which are a fraction of what they were just 50 years ago, would soon recover because when water clarity improves and life-giving sunlight reaches the bottom, those grasses emerge in all the traditional areas, thereby improving habitat for juvenile finfish and crustacean species. Those same grasses provide a significant portion of the winter dietary needs for migrating waterfowl. Those SAVs also improve the dissolved oxygen level in the bay's depths, locations where oysters and clams currently do not exist because of the incredible nutrient overload now taking place in the bay.
Yes, there is a drawback with zebra mussels - they will attach to any hard substrate, water intake pipes, pier pilings, rocks, etc... Of course, these are the same places where barnacles no longer seem to be able to survive, at least in depths more than 10 feet. That's because there is no longer any oxygen at those depths in mid summer. The same methods used to prevent barnacle attachment to these objects also works with zebra mussels.
So, for all you naysayers, those of us who reside near, and boat in the Chesapeake Bay, send those zebra mussels our way. We'll take em'. We would really like to see the bay's bottom once again, we would like to be able to eat the fish, clams, oysters, mussels, crabs, eels, etc.... We would love to see those SAVs clogging the rivers and the bay's shallows. I just returned to the bay from the beautiful waters of the Florida Keys. When I exited the James River into the bay proper and looked at the brown water I had to traverse to reach home I wanted to turn the boat around and head back to the keys. If you're old enough to remember to TV commercial about pollution where the American Indian stands on a hill overlooking an interstate highway with a tear falling from his eye, that's the way I felt when I returned to the Chesapeake.
Good luck on ever seeing the bay clean in any of our grandchildren's lifetimes - it ain't gonna' happen without the help of the zebras.