The interesting thing about working on Lake Saint-Pierre is that it is a very productive environment, one could even say a hyperproductive environment, because its average depth is around three metres. These shallow waters allow , light, which is essential for aquatic productivity, can to penetrate everywhere. The environment is therefore very productive. Lake Saint-Pierre has been called the breadbasket of the St. Lawrence. The lake acts as the river’s lungs because it purifies and reoxygenates water as it flows through the lake’s aquatic grass beds. It also acts as the kidneys of the St. Lawrence because it filters water flowing from Montreal to Quebec City. As this environment is very productive and very rich, it contains many living organisms, both animals and plants, from plankton to fish. It’sone of the most productive areas along the St. Lawrence River corridor. It therefore has high biodiversity and is a very interesting environment to study.
We have noticed fairly significant changes in fish population levels, especially when it comes to Yellow Perch, which were fished commercially for many decades. This fishery was quite significant for a lake with a surface area of 350 km2. A harvest of around 200 metric tonnes of Yellow Perch a year was sustained, which is a very large amount. That’s more than could be harvested in Lake Ontario. This demonstrates the high productivity of Lake Saint-Pierre. However, for reasons that we have identified, the population began to decrease in the mid-90s. Yellow perch stocks crashed, just as cod stocks did in Atlantic Canada. From 200 tonnes a year in 1994, over 5 years the harvest fell by up to 55 tonnes per year. That’s why commercial fishing in Lake Saint-Pierre has been shut down almost completely. We still can’tsay whether stocks are recovering, because it will take some time. However, I am working on this issue with my colleagues from the Ministère des Ressources naturelles et de la Faune. Currently, we are interested in finding out whether these changes are irreversible. Measures to protect Yellow Perch stocks after the crash were implemented in two major phases. First, the government launched a license buy-back. Commercial fishing licenses were reduced from 45 in 1994 to only 23 by the turn of the 21st century. Our models predicted that the population should have begun to recover within the three to five years of this major commercial fishing license buy-back. However, our studies showed no improvement in Yellow Perch populations five years after this first phase of significant measures. This is a signal from Lake Saint-Pierre that it is no longer capable of sustaining exploitation at the high rates that were harvested in the past. And now, there has been a second phase of license buy-backs. Only three commercial fishers remain on Lake Saint-Pierre. It is very important to keep a few of them, if only to show future generations the cultural heritage of Lake Saint-Pierre. Commercial fishing was part of our heritage. But, for all practical purposes, there is no longer any commercial fishery. We hope Yellow Perch stocks will increase in the future. Although there has been a huge decrease, from 200 tonnes per year to almost nothing, we hope that Yellow Perch stocks will show signs of recovery over the next few years.Is there anything we can do to improve this situation?
Various hypotheses have been advanced to explain the collapse of Yellow Perch stocks. One factor that we could change is intensive agriculture in the St. Lawrence floodplain, which deposits massive amounts of nutrients in the lake. These nutrients disturb trophic chains in Lake Saint-Pierre and can disrupt the balance of aquatic productivity and fish populations. Another hypothesis we have... These ideas are not verified. There is the whole issue of the city of Montreal’s sewage treatment plant which sends sewage our way that has not been completely purified or disinfected. This will be a huge challenge for everyone over the next decade. I am not putting the blame on the Montreal Urban Community. They are aware of the problem, and are trying to find solutions. This will definitely be one of the major challenges of the next decade. These are two factors we can work on. Among the other hypotheses, there is the variation in water levels of the St. Lawrence River. There have been very significant variations over the past few years. One of Lake Saint-Pierre’s most productive periods is during the spring flood. The water spills over the banks of the lake to create a vast floodplain where many species go to reproduce, to spawn among the reeds and aquatic plants. These floods contribute significantly to Lake Saint-Pierre’s high aquatic productivity. When the water level falls, when a year is drier and less rainy, each decrease of a centimetre in precipitation will result in the loss of several tens of square metres of breeding habitat. There is not much we can do to control this factor, although there are some possibilities. Upstream, the discharge of the river is controlled. We could intervene to some extent and we should try to do that in the future. Climate change also will definitely affect water levels in the St. Lawrence. According to some models, water levels near Montreal could decrease by one metre over the next 50 years, which would have dramatic repercussions on Lake Saint-Pierre. We therefore hope that these predictions are overly pessimistic and will not necessarily come to pass.
The Lampsilis is a research ship that we, the Université du Québec à Trois-Rivières along with five other Quebec universities, have obtained. It has provided us with an excellent platform for research. It is equipped with cutting-edge technology. The ship is 25 metres long and 7 metres wide and has a very shallow draught which allows us to navigate on the floodplains of Lake Saint-Pierre and on fluvial lakes like Lake Saint-Pierre and Lake Saint-Louis. It allows us to access areas and do research that we could not do before. The research we do aboard the Lampsilis is connnected to all fields of research covered by scientists in Quebec, from water quality to fish. The instruments aboard the Lampsilis are very sophisticated. There are two laboratories inside the Lampsilis. The ship can carry 12 people for longer stays. This allows us to carry out a wide range of research. For example, when it comes to fish research, we had never trawled in the river corridor because we did not have trawl-nets or any other suitable apparatus. Now, we are as well-equipped as oceanographic ships on the high seas. However, this ship is designed for the freshwater part of the St. Lawrence and allows us to study this environment in great detail.
