About ten years ago biologists discovered a tiny striped clam clinging to the bottom in Michigan’s Lake St. Clair. The mussel apparently hitched a ride from the Black or Caspian Sea on a Russian freighter. When the freighter exchanged ballast water, free swimming mussel larvae were dumped into the lake. This seemingly innocent exchange of water started the zebra mussel plague. Along with the zebra mussel, another exotic mussel known as the quagga, infiltrated the United States, as did several nuisance fish, such as the ruffe.
During the first five years, the two mussel species spread quickly and infested the Great Lakes and their tributaries. Today, these inch-long mussels infect 20 states in the central and eastern parts of the country. And the spread continues.
Vermont’s Lake Champlain is one of the newest areas of zebra mussel expansion. Pleasure boats and commercial barges coming into the lake from the Hudson River lock system gave the mussel easy access to the lake. California, Virginia and Connecticut also report recent infestations – again thanks to boats traveling across state lines.
The mussels are enjoying their newfound homes. Food is plentiful, and they have no natural predators in North America. With ample food and without natural controls, both the zebra and quagga mussels have prospered. That makes them a danger in their new environment.
Anglers visiting the Great Lakes, Hudson River, Mohawk River and Lake Champlain see thick colonies of mussels blanketing the bottom. They also attach to bridge abutments, pilings, docks, and even boat hulls.
The mussels also have a fondness for water pipes. They anchor near the flowing pipe water to feed on the plankton that gets sucked into the pipes. As the colonies grow, the mussel shells build up and clog the water pipes.
Electricity and water supply companies are spending millions each year to keep the invaders away from the water intake pipes. Public utility service crews also work hard clearing storm sewer tubes and flood control culvert pipes. Shorefront property owners are battling the creatures as well. Several times each summer, they must scrape the zebra mussel colonies off their boat docks, water pump supply lines, and boats.
The zebra mussel’s impact reaches beyond the physical costs associated with clearing water pipes and bottom structures. They have become an archenemy of trout and salmon anglers. These little mussels have devastated the coldwater fisheries in every body of water they infect.
Effect on coldwater fisheries
The zebra mussel and trout match-up is similar to the biblical story of David and Goliath. Only this aquatic story is totally reversed. The puny zebra mussel has amassed to Goliath proportions, dwarfing the largest trout and salmon. Unlike the bible story, this story does not appear to have a happy ending.
Zebra mussels are very efficient filter feeders. They can literally cleanse an area of plankton, which is the major food supply for baitfish – and gamefish fry. Eventually, plankton become too scarce to sustain the natural baitfish populations. As the baitfish starve, the food chain for the trout and salmon collapses.
A recent study on Lake Erie illustrates the effect. Diatoms, a microscopic single-cell alga, is the primary food of a tiny freshwater shrimp called diporeia, which is about the size of a large split shot. But as the zebra mussels filter the water clean of diatoms, the shrimp starve. Now, the shrimp population has plummeted.
Biologists routinely conduct shrimp population studies at various sites around Lake Erie. Prior to the zebra mussel’s introduction to the lake, the shrimp population was about 15,000 per cubic meter of water. A recent study found the same sampling areas almost completely devoid of shrimp.
The smelt is Lake Erie’s most important baitfish. They feed heavily on the diporeia. Following the predator-prey food chain relationship, the smelt population is dwindling too. The zebra mussels are impacting the entire food chain. Since 1995, when the smelt population crash was discovered, the Lake Erie lake trout population decreased by 65 percent.
Lake Erie’s tragedy is not an isolated situation. All the Great Lakes report some type of fisheries loss. More famed trout waters are also expected to show similar trends. The fisheries loss also forced many tackle shops and fishing guides to go out of business.
Effect on warmwater fisheries
While the coldwater fish battle the zebra mussel plague, the warmwater fisheries seem to be improving. Lake Erie now supports one of the best smallmouth bass fisheries in the nation. Largemouth bass fishing in Lake Champlain is perhaps the best it has ever been. This upswing in bass fishing seems to be directly correlated to the arrival of zebra mussels.
“I’ve seen the bass fishing improve in the rivers and lakes with zebra mussels,” says Frank Giner, a Danbury, Conn., angler who routinely competes on the Red Man tournament trail. “For example in the Mohawk River (New York) you used to see a team tournament win with ten bass weighing 11pounds. Now, a five fish limit will weigh that much.”
The most significant change that Giner and other anglers report is increased water clarity on the zebra mussel infested waterways. Zebra mussels efficiently filter the water by passing it through their fern-like gills to entrap algae and zooplankton. It is estimated that a single zebra mussel can filter one liter of water every day.
A side benefit to the mussel’s filtering system is the water clarity. The mussels not only clean the water of algae, but they filter out silt and mud as well. Rooted aquatic plants are now taking advantage of the cleaner water. Today, it is common in zebra mussel infested waters to find lush weedbeds growing in 20 feet of water. Before the zebra mussels came, rooted plants were limited to the very shallow portions of the lake.
“Back in the 60s and 70s, the water was pretty green and light penetration was low, only down 5 to 6 feet. Now the light penetrates much deeper,” says Ed Mills, Director of the Cornell Biological Field Station on Onieda Lake. One of Mills research projects is to monitor the effects of zebra mussels in New York’s lakes.
The expanded weed growth is the major contributing factor to the warmwater fisheries expansion. Weeds provide shelter for both the bass and their prey, particularly golden shiner and fathead minnows. The weeds also protect bass and yellow perch fry from excessive predation.
Bass can also access much deeper water, thanks to the expanded weed growth. Weeds produce oxygen through a process called photosynthesis. This oxygen remains somewhat concentrated around the weed beds that now grow out in deep water – water that was once devoid of oxygen. The bass seek out this oxygen-rich environment and stay near the weed growth.
Both largemouth and smallmouth bass, as well as northern pike, walleye and yellow perch now have plenty of oxygen, shelter, and spawn protection. The only missing piece of the puzzle is food. And for some odd reason, the warmwater fish food supplies have increased to support the fisheries growth.
According to Mills, the zebra mussels have dramatically altered the ecology of the infested lakes. He says besides clear water, the number of invertebrates has increased dramatically. Benthic shrimp, snails, and crayfish populations are all prospering in the zebra mussel’s environments.
“The mussels create structure on the bottom. The invertebrates utilize that structure to hide in and feed off the organic waste from the mussels,” Mills says. “From my perception, in general the Centrarchids, namely the sunfish and basses, are doing very well under the habitat the zebra mussels have created.”
Fishing the zebra mussel environment
The clear water has forced bass anglers to change their angling techniques. Giner says just a few years ago, you needed large brightly colored crankbaits and oversized spinnerbaits to catch bass in the dirty waters of the Hudson River and Lake Champlain. Rattles also were mandatory accessories for worms and jigs.
Now the bass, especially smallmouth bass, are responding to topwater lures. Giner believes the fish can see their target better in the clear water and are more willing to commit to the surface plugs.
“Lure color has become very important. Natural translucent patterns work better than solid patterns,” Giner says. “They reflect light better, and it flashes a lot more. It looks more natural to the bass.”
Giner also says he has greater success with lures that appear realistically. For example, he likes the Lucky Craft Sammy because the lure’s shape resembles a dying herring, a prominent baitfish in the Hudson River and Mohawk River systems. Other anglers report that transparent and “ghost” colored topwater lures, like the Zara Spook and Tiny Torpedo, have replaced the chartreuse and white poppers.
Likewise, natural colors are the colors of choice for soft plastics. Rootbeer, watermelon and smoke colored worms often produce better than solid black and purple worms, once popular in the stained waters. Metal flake in the soft plastic is now an important addition. In the cleaner water, the flash from the flake travels further to attract bass from longer distances.
Giner says he also traded his pork rind jig trailers for soft plastic crayfish-trailers. He says bass can study their prey very closely in the newfound clear water. The fish become wary of unnatural looking lures.
Finesse baits are also prime lures for zebra mussel lakes. Thus, the spider-type jigs and tube jigs, created for fishing the ultra-clear waters of the West, have taken the northern zebra mussel lakes by storm.
“While I know it’s not a good thing, the bass fishing has gotten better after the zebra mussels arrived,” Giner says.
Preventing the Zebra Mussel Spread
Anglers often travel from zebra mussel-infested water to zebra mussel-free water. For this reason, anglers are taking most of the blame for spreading the problem. Bass tournament anglers, like it or not, seem to get an even greater share of the blame because of their mobility between states.
All anglers and boaters can help stop the zebra mussel spread by doing the following:
1. Remove all vegetation from the trailer bunks, rollers, springs, and axles.
2. Thoroughly clean your craft. Wash the boat hull, the bilge, and thru-hull fittings with soapy 140-degree hot water. You don’t need boiling water or steam to rid the boat of zebra mussels.
3. Drain outboard motors of residual engine cooling water.
4. Allow the trailer bunks and boat to dry before launching.
5. Clean and dry boat livewells. Zebra mussel larva can survive for extended periods of time in the small livewell puddles. Bleach is a good chemical to clean and sterilize the livewell. Residual bleach in the livewell will not harm fish.