Zebra mussels were first noticed in New York waters in the mid-1980s. The thumbnail-sized freshwater mollusks are native to Eurasia and were inadvertently introduced into Lake Ontario in untreated ballast water that was routinely being discharged from transoceanic ships entering the Great Lakes through the St. Lawrence Seaway. It didn’t take long for the aggressive barnacle-like invaders to colonize both natural and manmade underwater structures like rocks, docks, piers, and municipal water intake pipes. I first became aware of zebra mussels in 1987 when I ran a charter fishing service on Lake Ontario out of Irondequoit Bay and saw mussel-clogged intake manifolds on some of the boats docked at the marina where I was based.
The rapid spread of zebra mussels is possible because of the combined effects of their high rate of reproduction and lack of natural predators. An adult female can produce more than 30,000 eggs per reproductive cycle and spawn up to five times per year. By 2005, they had invaded ten out of the eleven Finger Lakes with the lone exception being Canadice Lake. It’s thought that the lake’s 1,100-foot elevation has so far spared it from successful zebra mussel colonization. (The accompanying photo was taken at the state boat launch on Conesus Lake in 2012.)
Zebra mussel infestations are introduced in a number of ways. Aside from the ballast water discharges mentioned above, mussels also adhere to ship bottoms, anchors, and anchor chains, which enable them to hitchhike to new locations where conditions are suitable for colonization. In their earliest stage of development, free-swimming microscopic larvae known as veligers, drift for weeks in the water much like jellyfish and eventually attach themselves onto any appropriate hard surface. Mussels in both the larval and adult stages can survive for a week or more out of water and, once they have become established, either form can be transported from one lake to another on boat trailers and in the cooling systems of boat motors.
Zebra mussel infestations have had significant effects on the environment and the economy. As filter feeders, they upset the balance of nature by removing immense amounts of phytoplankton from the water column, which in turn increases light penetration and encourages weed and algae growth. They disrupt ecosystems and cause costly damage to power plants, harbors, ships and recreational boats. Any boat owner who has kept a boat docked for a month or more without periodically running the engine could find that zebra mussels have infested its intake manifold, which can cause the motor to overheat or perhaps not even run at all.
In 2007, I was being considered for an appointment to a regional director’s position with the New York State Department of Environmental Conservation. I convinced then-Commissioner Pete Grannis of the need to neutralize ballast water in order to prevent the further introduction of nonnative species into New York’s waters. He pursued the necessary legislation and a regulation that became effective January 1, 2012, requires ballast water be treated to eliminate all life forms before being discharged. The commissioner was successful in getting his regulation passed but I did not get the position.