Zeljko Djuric has been working with the local indigenous species, Signal crayfish (Pasifastacus leniusculus) for some 20 years. His company, Asturia Aquaculture Inc., has perfected breeding, spawning, juvenile and grow-out techniques on a small scale, but is ready to expand to commercial production.
“We were able to produce between 10 and 15 tonnes (20-30,000lb) annually at our Balkan facility,” recalls Djuric. “I am confident we could do that here on Vancouver Island as well.”
Djuric began with wild-caught broodstock. Although the Signal crayfish has a range across the U.S. Pacific Northwest and into the Canadian province of British Columbia, it has remained until now, a recreational fishery only.
His current outdoor facility is gravity-fed from an extensive aquifer just north of Duncan, B.C. The water, which does not require pre-filtration, flows through a series of ponds, and is piped through the hatchery and discharged into a wetland. Watercress grows throughout the wetland and while it helps to filter the water, it is also part of the crayfish diet and is sold to restaurants in nearby Victoria and Vancouver year-round.
Broodstock are spawned and held in lidded trays in standard Capilano aquaculture troughs. The troughs hold broodstock and juveniles together, each at a different depth to enable them to access different nutrients in the water column. Grow-out is in meter-cubed pens suspended in the ponds.
“We can have up to 1000 crayfish in each cubic meter pen,” says Djuric, adding that if the chemistry and feed is correctly balanced, the crayfish do not live up to their cannibalistic reputation. “When they are happy they don’t eat each other,” he explains.
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Six-foot round tanks hold what Djuric describes as “compost,” a culture of duckweed and plant waste, including watercress trimmings, that forms a biofloc supporting the water chemistry and providing a supplemental source of feed.
“We are using all-natural feed,” says Djuric. “They are basically scavengers and we are using mostly plant material.” One of the intake ponds is used to culture duckweed (Spirodela polyrrhiza), an invasive species on Vancouver Island, but a key feed ingredient for the crayfish.
Djuric adds the company is developing diets with Fisheries and Oceans Canada researchers. “We are working with a multi-trophic system,” says Djuric. The waste from the crayfish can fertilize the duckweed, which the crayfish eat, and some of the waste supports the watercress. “Depending on water temperatures, we are looking at two years to grow-out, post hatch,” he says.
Djuric’s Asturia Aquaculture has entered into a partnership with the local Malahat First Nation. They have constructed a grow-out site at a former cement quarry and expect to be in commercial production by June, with the capacity starting at 1000 lb. per week with plans to increase production to 2000 lb. per week. They have a target price of $20 per lb. wholesale.