Krill and capelin: prized prey

The life of krill: shaking it up

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  • Krill
  • Photo credit: © Fisheries and Oceans Canada, J.-F. Sylvestre

In the Norwegian language, krill means “whale food”, but this tiny, translucent-coloured crustacean is sought by numerous species of fish and seabirds. Areas where krill concentrate in deep waters or occasionally near the surface attract whales, who gulp them down by the hundreds of kilos. The blue whale can consume 1 tonne of krill a day. Even if they resemble shrimp, they aren’t. They are smaller, measuring just one to four centimetres. They congregate in clouds that can reach several kilometres long and up to 100 m thick.

…bioluminescence and hairy legs

With their 22 feet, adult krill are rather strong swimmers that can achieve vertical migrations in the water column to avoid their predators. During the day, they prefer to remain in dark, deep water and rise closer to the surface at night. The hair on their legs serves as a filter to capture food. They have special organs that are capable of emitting light (bioluminescence).

Declining stocks

According to studies conducted since 1994, krill made up 70% of the zooplankton biomass of the Estuary and the Gulf up until 2003. They have since been supplanted by Themisto libellula, an amphipod from the Arctic, and now only represent 40%. Around the world, krill are harvested for aquaculture and their oil, which is rich in Omega-3. in order to safeguard the entire food chain, harvesting krill in Atlantic Canada and in the St. Lawrence was prohibited in 1998.

A little fish that “rolls” and feeds whales

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  • School of capelin
  • Photo credit: © Fisheries and Oceans Canada

This small olive-coloured fish with silvery sheen measures approximately 15 cm. With a life expectancy of five to six years, it lives and travels in compact schools in cold waters. It feeds on plankton and reproduces between mid-April and early July in deep waters, but also on the banks of the Estuary and the Gulf, a phenomenon that occurs especially at night. People gather on the beaches to watch and reap the capelin “rolling” in the waves, in schools so dense they can be harvested with shovels and buckets. Females lay up to 50,000 eggs, which are reddish in colour and measure 1 mm in diameter, and which are then buried approximately 15 cm deep in the substrate. The larvae develop before hatching and departing with the tide for a life in open water.

A fragile species sensitive to change

A species of cold, pelagic waters, the capelin is expanding its range in the context of global climate change. Since the 1980s, it is increasingly present in the southern portion of the Gulf, the Estuary and the Scotian Shelf, probably due to colder waters entering the intermediate layer of the St. Lawrence. But water that is too cold stunts the growth of juveniles and reduces their size. The species is losing reproduction habitat due to shoreline erosion and infrastructure such as riprap. Efforts are being made to acquire a better understanding of this species, as well as to document capelin spawning locations. A decline in its abundance might have negative impacts on the fate of the majority of marine species, the whale-watching industry and commercial fishing. In 2003, the Capelin Observers Network (CON) was created. To receive or report information on capelin spawning grounds, dial 1-877- Ça roule (227-6853).