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Fish food

Fish food

[photo of Connor Elliott and Bruce Tufts at the Freshwater Fisheries Conservation Lab at Queen's]
Bernard Clark

Graduate student Connor Elliott and Professor Bruce Tufts measure the oxygen levels and temperature in a tilapia tank at the Freshwater Fisheries Conservation Lab.

The decline of many wild fish populations is a big problem, both in Canada and around in the world. Wild fish populations are no longer able to keep up with the demand for fish for human consumption. Aquaculture, the farming of fish for human consumption, has become an important way to fill this gap. But aquaculture, as it turns out, has some serious environmental problems when it takes place in open net pens in natural waterbodies. One of the big problems is that nitrogen-rich waste created by the dense fish population flows out of the pens and reduces the quality of the surrounding water for other aquatic life.

But nitrogen-rich water is perfect for growing produce hydroponically, without soil. Aquaponics systems (a form of inland aquaculture) grow both fish and plants in the same recirculating water system. In the Freshwater Fisheries Conservation Lab at Queen’s, Bruce Tufts and his students are working to improve aquaponics technology to make systems that work well in a Canadian climate. Ideally, inland aquaculture systems could be adopted in Northern parts of Canada in areas where conservation of wild fish populations and the paucity of fresh produce are a real concern.

Tilapia, a freshwater fish, has grown in popularity in recent years as a food fish. Most of the cultivated tilapia currently available in Canada comes from South America. Growing more fish locally through aquaponics would significantly cut down the carbon footprint required to get food onto Canadian tables. And as a bonus, one can grow a variety of healthy produce at the same time, even in the dead of winter.

Tilapia thrive in an aquaponics system. At the Queen’s lab, wastewater from large tanks of tilapia is filtered and then run through pipes into the next room, where rows of healthy kale, Swiss chard, lettuce, and basil grow. After passing through the plant trays, the water is pumped out again and reheated to a balmy 30 degrees, before going back into the fish tanks.

[photo of Connor Elliott in the produce room of the Freshwater Fisheries Conservation Lab]
Connor Elliott in one of the produce rooms at the Freshwater Fisheries Conservation Lab at Queen's. Photo: Bernard Clark 

In another room at the lab, walleye swim in water that’s a tad cooler, about 20 degrees. Without the variations in water temperature that exist in Ontario’s lakes, these fish will grow to market size in about a year, instead of the normal three to four years in the wild. Walleye, also known as pickerel, is one of the most popular food fish harvested from freshwater lakes and rivers in Canada. A number of factors, including excess harvest and environmental conditions that affect fish habitat, have placed strains on many wild walleye populations.

Here in the lab, both fish and plants grow in optimal conditions. The fish aren’t harmed by pollution or predators; the plants are safe from frost, disease, and insect damage. Some of Dr. Tufts’ students examine the way that water chemistry affects different types of produce. Others are looking at the best types of feed for the fish: they’ve discovered that tilapia will grow well on feed that incorporates a significant amount of algae, which is both easy and cheap to produce. The aquaponics research in the Freshwater Fisheries Conservation Lab at Queen’s and a number of other research and educational projects in the Department of Biology were made possible by The Greenberg Family Fund in Conservation of Freshwater Fisheries.

[cover graphic of Queen's Alumni Review, issue 1-2018]

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