Euphausiids (Krill)
Euphausia pacifica. Photo credit: DFO.
On this page
- Species overview
- Fishery history
- Ecosystem context
- Integrated Fisheries Management Plan
- Sources
- Related links
Species overview
Physical description
Euphausiids are shrimp-like crustaceans. They are commonly known as krill. There are more than 85 species of krill around the world. The smallest are only a few millimetres (mm) long. The largest deep sea species reach 15 centimetres (cm) long.
Distribution
Most krill species are pelagic, meaning they live in deep waters (at least 200 metres (m)). At night, juveniles and adults swim to the surface to feed. They avoid predators by returning to deeper, darker waters during the day.
About 23 species of krill live in British Columbia (BC) waters. The 6 most common are:
- Euphausia pacifica
- Thysanoessa spinifera
- Thysanoessa inspinata
- Thysanoessa inermis
- Thysanoessa longipes
- Thysanoessa rashii
Euphausia pacifica accounts for 70% to 100% of biomass in the Strait of Georgia. It lives:
- along the shelf
- on the shelf slope
- in inland waters
Thysanoessa spinifera lives along the shelf and on the shelf slope. T. inspinata lives on the shelf slope and in oceanic waters. T. inermis, T. longipes, and T. rashii live in inland waters.
The krill population in the Strait of Georgia varies in size seasonally and between years. This is mainly driven by climate and predator effects.
Euphausia pacifica life cycle
Male Thysanoessa spinifera. Photo credit: DFO.
Euphausia pacifica usually spawn between May to July in BC, but it can begin as early as March or April. There is a second, smaller spawning season in late August to September.
Adult males make packets of sperm called spermatophores. Spermatophores attach to the outside of the female reproductive tract. Eggs are fertilized and released into the water. Eggs float to the surface and hatch into larvae.
Eggs and larvae are vulnerable to predators. If they survive, they molt as they grow through multiple larval stages into juveniles and then adults. In the Strait of Georgia, adult krill stop growing in fall and winter when water temperatures and phytoplankton are low. Euphausia pacifica can live for 19 to 22 months.
Fishery history
Krill are social and gather into dense patches. This behaviour makes them easy to collect in a net. The commercial krill fishery began in 1970 in the Strait of Georgia. It was an experiment at first. It changed from scientific licenses to general purpose commercial licenses in 1983.
Today, the fishery remains small within the Strait of Georgia and a few mainland inlets along the south coast of BC. Krill are harvested by fine mesh plankton trawl nets. Catch is limited by low participation with few buyers and processors involved in the fishery.
Krill must be frozen 7 to 12 hours after being caught. There are 2 types of vessels in the fishery:
- freezer vessels
- fresh vessels
The daily catch of freezer vessels is limited by freezer capacity. Fresh vessels have tanks to keep krill alive. They can catch more krill for onshore processing and freezing.
Most of the commercial harvest of krill is used for aquaculture fish food. A small portion is used for aquarium pet food. There are also developing markets for krill as:
- human food products
- food additives
- biochemicals
- enzymes
- protein concentrates
The krill fishery is a managed through:
- area-based quotas
- seasonal openings
- Total Allowable Catch (TAC)
- fishery notification
- dockside validation program funded by harvesters
First Nations are not known to harvest krill for Food, Social or Ceremonial (FSC) purposes. Recreational fishing for krill is permitted by dip net.
Ecosystem context
Krill are mostly herbivores early in life. Some species become omnivorous as they age.
Krill are an important part of the marine food web. Krill is part of one of the shortest food chains: it feeds on phytoplankton and then is fed on by:
- fish
- seabirds
- marine mammals
Some predators, such as Blue Whales, eat only zooplankton, mainly krill. The amount of krill eaten by some fish can also be quite high, depending on the age of the fish and season up to:
- 84% of Pacific Hake diet
- 89% of Spiny Dogfish diet
- 100% of Pacific Herring diet
From 1985 to 1997, the fish community off of the southwest of Vancouver Island was estimated to have eaten 297 kilo-tonnes of krill every August. That’s over 650 million pounds in 1 month!
Distribution of krill influences the movements of predators. For example, Humpback Whales shifted away from the south-west coast of Vancouver Island after a decline in krill. Humpback Whales are now returning to the Salish Sea in greater numbers.
Integrated Fisheries Management Plan
Integrated Fisheries Management Plan for Euphausiids
Sources
- Boldt, Joyce, Tucker, Gauthier and Jackson (2025). State of the physical, biological and selected fishery resources of Pacific Canadian marine ecosystems in 2024. Can. Tech. Rep. Fish. Aquat. Sci. 3687: viii + 337 p.
- Heath (1977). The ecology and harvesting of euphausiids in the Strait of Georgia. Ph.D. thesis, University of British Columbia, unpublished.
- Mauchline and Fisher (1969). The Biology of Euphausiids. Advances in Marine Biology. Volume 7.
- Robinson (2000). The consumption of euphausiids by the pelagic fish community off southwestern Vancouver Island, British Columbia. J. Plankton Res. 22(9): 1649-1662.
Related links
- Date modified: