JI made a trip to Quebec, along the St. Lawrence River, to study the acoustics of belugas (Delphinapterus leucas), to photograph and understand whales, and to help and get to know the Groupe de Recherche et d?Etude des Mammifères Marins (GREMM) in Tadoussac.
Since observations at sea or on the coast, we are amazed to see so many whales in Tadoussac, Escouminns or Grandes-Bergeronnes. Some can even be seen feeding on the surface, a magical moment.
All this is due to an oceanography and currents or tides and winds, favoring an exceptional regional biological production. A unique place located in a marine park created in 1998 and which responds to an ever-increasing tourist demand for whale watching.
The three currents and the tide:
The St. Lawrence River is one thousand six hundred kilometers long and starts in the great American lakes and flows into the Atlantic:
There are three strata of water in the river:
- the surface layer
- the cold middle layer
- the deep layer
The salty water of the North Atlantic rises through the Laurentian Current at depth, and the fresh surface water sinks back into the Gulf and the ocean. These two layers will oppose each other.
The tides created by the attraction of the moon and the sun on the ocean, play a determining role in the contribution of salty and cold sea water rich in nutrients. The narrower the place, the higher and more important the incoming tidal wave will be. It can vary from three to eight meters.
At Tadoussac, the Saguenay Fjord brings its freshness to the St. Lawrence Estuary. All these factors, along with the wind, play an essential role in the feeding of the whales.
Plankton:
In order to understand whale feeding, we need to know what interests them.
Plankton, the base of any marine food chain, is fundamental to the trophic chain.
It is composed of many planktonic organisms including phytoplankton and zooplankton. Their life span is about two years.
The first is made up of planktonic algae which will serve as food for the herbivorous and carnivorous zooplankton. This one needs solar energy for photosynthesis and nitrogen found in ammonium and nitrate.
The krill or euphausides, is a zooplankton which like all the others does not like the light. During the day, it will stay at depth to hide from predators and at night it will come to the surface to feed on phytoplankton. When they reach adulthood, they move vertically and avoid being too deep or too close to the surface. The larvae, as for them, will let themselves be carried along by the current.
Baleen whales feed mainly on krill. A blue whale (Balaenoptera musculus), which can reach up to thirty meters long and weigh one hundred tons, fills up on food before winter and eats three to four tons of krill per day.
The embankment and plankton trap:
The Laurentian Channel is three hundred to five hundred meters deep. At the end of the channel, there is a large concentration of plankton that runs up against slopes and towards the surface. A mass that can reach several kilometers long and a hundred meters thick.
The slope has a steep topography, near Île Rouge and the Saguenay Fjord, opposite Tadoussac.
In this abundance of euphausids, females will lay eggs and adults will reach the end of their journey. There is then an incessant back and forth between the surface layer which pushes the krill larvae towards the Gulf and the intermediate layer which makes them return.
Organic debris will continuously settle on the bottom, but the deep currents will bring them up (upwelling), accompanied by the high tide, and mix with the fresh water. This is the brackish color that we find rich in nutrients.
It is a necessary food supply for the krill, but trapped in front of a dead end, it will be pushed towards the surface.
In addition, it will occur as a pump effect boosting the mixture towards the Gulf.
The Whale Feast:
The whales choose to come to Tadoussac because of this concentration of food.
Some feed on capelin, sand eels or herring and copepods, depending on the tides and cold waters. All these pelagic fishes will eat in the same place.
The whales are often found at the head of the Laurentian Channel, along a water depth of one hundred meters.
The whales of excursions know the place where you can find up to fifty boats in the same area!
They fatten in a plankton cul-de-sac, bringing a targeted density, without being obliged to make efforts and to spend too much energy. We observed that they stay longer at the surface at night to filter the krill coming up from the deep. But there are still questions about the feeding of the whales because they spend ninety percent of their time underwater.
Apart from the beluga whale (Delphinapterus leucas), which stays in the St. Lawrence all year round, the fin whale (Balaenoptera physalus), the blue whale (Balaenoptera musculus), and the minke whale (Balaenoptera acutorostrata) are regular visitors to the area and feed before migrating in winter.
Species such as humpback whales (Megaptera novaeangliae) and sperm whales (Physeter macrocephalus) are seen a few times. All others are exceptional in the area of Tadoussac, Les Escoumins or Grandes Bergeronnes, except in the Gulf of St. Lawrence.
The whales return to the same place for years, knowing very well the topographic relief and locating the planktonic mass. They follow the tides, temperature and salinity and communicate with each other.
All these geographical phenomena affect the frequency of whales in the same place from one year to the next. The responsible people who study whales and its oceanography do their best to protect them, by monitoring global warming, maritime traffic or pollution.
This region is a major whale gathering place. Let's enjoy the pleasure of seeing them while there is still time.
BIBLIOGRAPHY :
(1) Regional workshop on marine mammal observation activities at sea, summaries of scientific research projects, Saguenay-St. Lawrence Marine Park, May 1998.
(2) Whales of the St. Lawrence, Research and Education: A Passport to the 21st Century, G.R.E.M.M., 1998.
(3) Newsletter "Le Souffleur" since 1989, G.R.E.M.
(4) Marchand Caroline, Simard Yvan and Gratton Yves, Concentration of capelin (Mallotus villosus) in tidal upwelling, fronts at the head of the Laurentian Channel in the St.Lawrence estuary, NRC/CNRC, vol.56, number 10, 1999.
(5) Simard Yvan and Lavoie Diane, The rich krill aggregation of the Saguenay - ST.Lawrence Marine Park: hydroacoustic and geostatiscal biomass estimates, structure, variability, and significance for whales, NRC/CNRC, vol.56, number 7, 1999.
(6) Simard Yvan, Comment la mer nourrit-elle les baleines à Tadoussac ou Le pourquoi océanographique de la visite estivale des rorquals dans l'estuaire maritime du St.Laurent, à la tête du chenal Laurentien (Tadoussac, Les Escoumins, Grandes-Bergeronnes), l'Euskarien, Les Sciences de la Mer, p 33 à 38, été 1994.
(7) Rossignol Anne, L'Estuaire maritime et le golfe du Saint - Laurent, Carnet océanographique, INRS / Océanologie, 1998.
(8) Michaud Robert, Rencontre des baleines du Saint - Laurent, G.R.E.M., 1993.
(9) G.R.E.M.M websites: http//www.gremm.org and www.baleinesendirect.net or www.whles-online.net
Two pages article in Planète Mer n°29
S.O.S Big Blue - January - February - March 2001
by Julien Marchal
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