A translation by Judith Turcotte.
Invasive species modify the biodiversity of the St. Lawrence. In our river today, we find species, plants, mushrooms and micro-organisms that were not there a few years ago. More than 180 invasive species are identified. We are not the only ones experiencing this phenomenon; more than 37,000 invasive species have been identified in the world. These invaders supplant the indigenous species and modify the biodiversity.
In my last two blogs, I wrote on the invasions of the zebra mussels and the Asian carp and I could continue on this theme for several weeks. I am thinking in particular of the spotted goby that gorges on zebra mussels without eliminating them. The gobies are present in the river, however, have not yet invaded its tributaries. There are also the green crabs which are approaching the Magdalen Islands. The green crab is one of the “10 most undesirable species in the world” according to Fisheries and Oceans Canada. The latter feed on seagrass (eelgrass), an essential habitat for our fish and lobsters.
Some of the invaders arrive from the Great Lakes, others come from the South like the green crab which started invading the American coast in the 1800s. Their migration to the north was slow and it was only in 1980 that they reached Nova Scotia. Each invasion has its history but one that struck me was the arrival of the tench in the St. Lawrence River. The tench is a freshwater fish native to Europe and Asia. The arrival of the tench dates back only forty years. Around thirty specimens were illegally imported from Germany in 1986 in order to start breeding in ponds on the edge of the Richelieu. In 1991 following the floods, the tench escaped the ponds and entered the Richelieu. What strikes me in the tench’s history is the speed with which it invaded the St. Lawrence River. From thirty to thousands in a few years.
The invasive species are not the only ones causing problems. Plants have also invaded our waters. Among others, we find the water chestnut that form dense colonies that stifle the aquatic biodiversity and the Eurasian watermilfoil that alter the fish’s reproduction habitats and reduce the water’s oxygenation. These plants arrive in the ballast water of ships. It is impossible to get rid of these invaders. We must learn to live with them.