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Andre Martel is passionate about mussels but knows that at the mere mention of the word, most people immediately think of steaming piles of black shells drenched in some tasty exotic sauce.
The Canadian Museum of Nature malacologist—don’t call him a mussel man—would like us to cast aside those culinary images, spare a thought for the mussels submerged in the Ottawa River and know what a remarkable environmental service they perform in their role as natural cleaning agents.
And clever little creatures—“animals,” insists Mr. Martel—they certainly are. Of 54 known species of mussel in Canada, 41 can be found in Ontario. At least 15 of those species reside in the Ottawa River, making it one of the most mussel-rich waterways in the country.
So what? Why should we care?
It’s a question that Mr. Martel is only too happy to answer and in as much detail as you like. But the bottom line is this: if you enjoy swimming or fishing in clean water, thank a mussel.
Freshwater mussels are super-efficient, hard-working water filters pumping water through their shells while simultaneously consuming minute food particles such as algae, bacteria and other bits and pieces of refuse. A crowd of pulsating mussels creates a formidable filter, working for the most part from April through November, though some continue working under ice throughout the winter.
“Look closely as you wade near the shore,” says Mr. Martel, who works out of the Museum of Nature’s laboratory and office complex in Gatineau. “Freshwater mussels with their shells gaping open and their siphonal apertures wide open, feeding and filtering at the same time.”
The other major environmental task performed by mussels is the churning and oxygenating of river and lake sediment. The visible evidence of this are the trails mussels leave when they travel.
“This is done with a muscular foot, allowing the animal to burrow into gravel, sand or mud and plow through the sediment,” says Mr. Martel. “It oxygenates the bottom and increases productivity and diversity of life forms living there.”
And though it isn’t apparent, mussels have sets of functioning organs and a nerve system approximating a brain—being entitled, therefore, to the designation of “animal.”
And like most living things, they are especially smart when it comes to procreation. Mussels of all kinds are keen on perpetuating their species and populating as many rivers and lakes as possible.
To achieve this, some female species have developed the exceptional ability to disguise themselves as tiny minnows to lure unsuspecting big fish.
Here’s why. Mussels carry their eggs in special gill pouches and after the eggs develop into larvae (about the size of a grain of sand), the mussels seek out fish to transport them along the waterway. To achieve this, the female mussel must first attract a fish through its cunning luring technique. When the fish swims over to check out the “minnow,” the mussel squirts its embryos onto the fish’s gills or fins where they stick. A few weeks or months later, depending on the species, the surviving embryos develop into tiny mussels, drop away from the fish and continue their lives on the bottom of the river.
One species of mussel, the rare olive hickorynut, is fussy in that it will only squirt its larvae onto sturgeon. Mr. Martel is currently studying the Canadian status of the olive hickorynut, but he speculates that the mussel’s rarity is connected to the depletion of sturgeon in our rivers.
The scientist is also closely studying what he enthusiastically considers “a rare and awesome shell” in the Ottawa River called the pink heelsplitter, which sounds less threatening under its Latin designation, Potamilus alatus.
When most of us see mussels in rivers and lakes, we’re likely looking at the more common eastern elliptio, eastern lampmussel, the plain pocketbook or perhaps the fatmucket, which is especially adept at that minnow disguise. The sad reality, of course, is that while the worthy fatmuckets, pink heelsplitters, and their kind labour for the good of nature in relative anonymity, the bad guys of musseldom—the dreaded zebras—have achieved the greatest renown.
Zebra mussels, unwelcome invaders native to the Caspian Sea and Ural River in eastern Europe, rode to North America in the ballast water of a trans-Atlantic merchant ship and were emptied into the St. Lawrence Seaway and Great Lakes.
Since they were first sighted 18 years ago, they have spread as far south as Texas. Zebras are workaholic water filters, but when it comes to spawning, they have an advantage over other mussels because they don’t need fish to carry their eggs. Zebra mussel larvae disperses at the will of currents and travels upstream on dirty hulls and boat trailers. Scientists fear that the zebra’s superior reproductive ability—and predatory nature—will ultimately spell the end of all domestic mussel species and cause other permanent upsets to North American waterlife. What is not in dispute is the costly damage they cause industrial drainage pipes.
If boaters were more diligent about cleaning their craft, says Mr. Martel, it would do much to thwart the proliferation of the zebra mussel.
“If you leave your boat long enough for the hull to get just a little dirty,” he adds, “and you haul it on a trailer upstream, or to another watershed that has no zebra mussels, chances are you will introduce zebra mussels to that waterway—especially if it’s an overcast day and not too hot.”
For all Mr. Martel’s vast knowledge of the mussel, he is the first to admit that he and his fellow researchers still have vast amounts to learn.
“It’s fascinating work and will continue to occupy graduate students and aquatic biologists for decades.”
– This is the eighth in a multi-part series that takes a close look at the flora, fauna and formations of our region. Next Saturday: The three-spined stickleback.
© The Ottawa Citizen 2006