Six or seven years ago, a transoceanic ship discharged freshwater ballast into one of the Great Lakes to start a series of events that have struck home in Carroll County.
That is how fisheries scientistsin Ohio figure the zebra mussel hitchhiked to North America from Europe. Quickly, Lake St. Clair was infested, then Lake Erie, followed by others in the Great Lakes chain and, eventually, spreading into NewYork and the St. Lawrence River.
Infestations were detected last year in the upper Susquehanna River. And within the past two weeks, Liberty and Prettyboy reservoirs were closed to boating by Baltimore City in hopes of keeping these damaging shellfish from overrunning the lakes.
No one can guess when and if the ban will be lifted -- and this is only the beginning of what might well be the environmental problem of the decade.
The zebra mussel is a tenacious critter whose colonies clog filtering screensand pipes in water lines, where they can reduce water flow by as much as 90 percent.
But this is only the tip of the iceberg. Hardy, stubborn and prolific zebra populations are considered capable of great adverse impact on ecosystems that could affect fishing and most marine life as they cover bottoms, ledges and lake structure.
Studying this problem since it first became apparent several years ago, marine scientists at Ohio State University reported that "most authorities consider the spread of zebra mussels across North America to be a certainty."
Imagine them disrupting the fragile ecosystems of our trout streams, and also the upper Chesapeake Bay complex. The Baltimore City Department of Public Works reacted quickly -- some complain too quickly -- but no one can argue that precautionary measures are notin order to protect the 1.5 million people who depend on reservoir water.
The ban, which apparently was only considered for about a week before implementation, will affect far more than the several thousand boat fishermen who regularly cast into Liberty on the Carroll-Baltimore line and Prettyboy, just a couple of miles away in Baltimore County. As usual, Loch Raven in Baltimore County will be open only to rental boats.
Other reservoirs may be added to the list in an attempt to avoid infestations. Businesses that cater to fishermen, especially tackle shops, are bound to feel repercussions.
At Fish Maryland Bait and Tackle on Liberty Road in Eldersburg, proprietor Larry Dobrovolny wonders what can strike next on the fisheries front.
One-quarter to one-third of his business is dependent on 1,800 boat-permit holders who fish the reservoirs. While some speculate shorelines could be crowded with shore fishermen, he said reservoir boat fishermenwant to fish from boats -- and will do so -- but in other places, especially in Pennsylvania.
"I'm not alone," he said. "Those who sell boating products will also feel the pinch. That's big business, andreservoir boatmen spend a lot to rig up for bass."
Dobrovolny said he was considering hiring a couple of part-time workers for the summer, but now has doubts. He is concerned about the future of his reservoir-dependent business.
Jack Barnhart, who operates Outdoor Sportsman in Essex, Baltimore County, and Tommy Tochterman, founder of Tochterman's on Eastern Avenue in Baltimore, said reservoir fishermen play a big role in their businesses.
"The shock has just hit home,"said Barnhart. "No one knows what to do."
Nor do Baltimore water officials. Contrary to rumors that plans to lift or modify the ban are imminent, a spokesman said the other day that no such plans are on the drawing board.
Officials are still trying to assess the potential of zebra infestations, while emphasizing that preserving the reservoir water system is the prime consideration. The spokesman could not give a timetable for any decisions.
One thing is known. Zebras, like gypsy moths and hydrilla, are notorious hitchhikers. In either their veliger or adult stages, the mussels can be transported and "stocked" via boat hulls or live wells -- something akin to how dreaded hydrilla arrived in the Potomac a decade ago, but with a much happier ending. There, the marine weed actually helped bass fishing, though it did clog many open waters.
Zebra mussels can survive 10 to 14 days on or in boats out of the water. One part chlorine mixed with 10 parts water can kill them, but officials wonder how thoroughly boats, motors and live wells would be cleaned by boaters after visiting infested waters.
This is only the beginning of the story, so stay tuned.
FACTS ABOUT ZEBRA MUSSELS
* Within four years after introduction, zebras had colonized the surfaces of every firm object in Lake Erie.
* Any firm surface that is not toxic can be colonized, including rocks, metal, wood, vinyl, plants, glass, rubber, fiberglass, paper, even other colonies. The surface need only be firm, though some have been detected on soft muddy bottoms.
* Though they are most successful at depths of 10 to 23 feet, infestations have been found at depths of 164 feet in Italy. And they need only moderate water temperatures.
* They are filtration feeders; waters are strained through their systems, and they eat mostly algae along with some phytoplankton. And what crucial phytoplankton is not eaten is bound with mucous into pellets unusable by other creatures.
* There are few natural enemies for the zebra. Ducks, especially canvasbacks, old squaws and scaup eat them, but in many areas of infestations the waters are frozenover when diving ducks are present. Virginia Institute of Marine Science is evaluating the effect of hard shell crab appetites on the mussels, but again the two encounter each other infrequently. A few fishdo feed on them, including yellow perch, but apparently not to an appreciable degree.