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Quebec Bulletin
August-September 2015/Volume 18/Number 4

The St. Lawrence Estuary: A Whale's Pantry

Krill
DFO – J.-F. St-Pierre
Northern krill.

The Estuary and Gulf of St. Lawrence encompass major summer feeding grounds for large cetaceans like the blue whale, fin whale and common minke whale, that forage there. A Fisheries and Oceans Canada team of scientists recently plied the St. Lawrence, from the head of the Laurentian Channel to Gaspé, on their eighth annual survey of the area to study how forage species such as krill and sand lance affect baleen whale distribution.

The mission was carried out aboard the mid-shore research vessel, CCGS Frederick G. Creed, from August 1 to 20, ultimately to create spatiotemporal maps of the whales' prey in order to identify the boundaries of their feeding grounds.

Data were gathered using a modified plankton net (JackNet) to catch krill, along with sophisticated hydroacoustic equipment used to probe the water column with sound waves. The team, made up of Ian McQuinn, Stéphane Plourde, Pierre Joly and Jean-François St-Pierre, will use this data to develop an inventory of the distribution of zooplankton, particularly krill and small pelagic fishes like herring, capelin and sand lance.

Modelling the layers of krill at the head of the Laurentian Channel.

A hydroacoustic image of krill at the head of the Laurentian Channel.
The krill density increases from green to yellow to red.
The solid dark line is the sea floor and the scale on the left indicates the depth in meters.

This mission is part of Fisheries and Oceans Canada's Aquatic Species at Risk Program. A detailed analysis of the results of this mission will show the density and distribution of forage species while also establishing a quantitative index of abundance for various krill species.

Did you know? The blue whale is oligophagous, meaning it depends essentially on only one food source, in their case euphausiids (krill), although copepods may also account for part of its diet.

For more information:

Ian McQuinn
Science

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