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Enormous whales, belugas and seals are found in the
St. Lawrence River. These marine mammals are drawn by the abundant food found
in these waters, as are the hundreds of thousands birds
living in the area. Fish and shellfish are caught
as food by humans, though quotas are established to prevent overfishing. Did you
know that laws exist to protect endangered animals, plants
and habitats? And there are many fun facts
to learn about the river!
The St. Lawrence is home to thousands of interesting plants and animals living
in perfect harmony. But the slightest upset to this environment can have devastating
consequences. For over 20 years, scientists have been studying the flora and fauna
of the St. Lawrence in order for us to gain a better understanding of life in
and around the river. Sometimes, they found it necessary to sound the alarm. Learn
more about the seaway, a thriving habitat.
Zealous zebra mussels
Zebra mussels, originally from the Caspian Sea in Russia, first appeared
in the Great Lakes 20 years ago. These mollusks were undoubtedly
introduced here by a ship emptying its ballast in North American
waters (See Polluters by
night).
Today, zebra mussels are a pest. They damage ship hulls and motors,
wharf pillars and water pipes. This fresh water mollusk glues itself
rather tightly to any hard substance located underwater, including
the backs of crayfish and other mussels!
But it appears we will have to learn to put up with them since zebra
mussels have contaminated many bodies of water in Canada and the
United States. A single mussel can lay up to 1 million eggs a year!
Nearly invisible, zebra mussel spawn drift with the current and can
be quickly carried to a new location in two or three weeks. Upon
arrival in their new home, the spawn form a shell, then grow into
adulthood.
Zebra mussels feed on minute plant and animals in the water. Each
mussel can filter up to a litre of water a day. Not bad for a creature
the size of a hazelnut!
The problem posed by zebra mussels is that they consume much of the
food at the bottom of the food chain, leaving very little food for
other species of mussels and fish. What would happen if the zebra
mussel population continued to grow unchecked? Some native species
would disappear, being starved out of existence. This, in turn, would
lead to the disappearance of other species. You know the law of the
underwater jungle: big fish eats little fish!
But this "sticky", bothersome visitor is also dangerous
to humans. The shells of dead zebra mussels are very sharp, so if
you go swimming barefoot in a lake or river, be careful!
Worst of all, zebra mussels are not good eating! It seems their only
saving grace is their pretty name!
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