Something Fishy?
Wild versus Farmed
Much of the seafood we consume is from the wild but, increasingly, we're eating products of aquaculture, or fish farming. Aquacultured fish aren't genetically modified; in fact, the industry group, the Canadian Aquaculture Industry Alliance (CAIA), frowns on that. But, like other farmed creatures, the fish are raised in confined areas, fed prepared feed and sometimes given drugs.
There are fish farms in every province and in the Yukon, mostly in lakes and oceans but sometimes in land-based tanks. They produce a wide range of species, including salmon, trout, mussels, oysters, tilapia and Arctic char, with halibut, haddock and cod emerging as promising newcomers.
Salmon is by far the most popular farmed fish. "If you're buying Atlantic salmon, it's farmed," says David Rideout, executive director of the CAIA. (Pacific salmon is still mostly wild although aquaculture is gaining popularity there, too.)
At a hatchery, salmon brood stock are put into incubation tubs to spawn. The newly hatched fish are placed in fresh water feeding tanks, then transferred to sea water sites at seven to eight months, mimicking what happens in nature. The salmon are kept in anchored metal or plastic cages in the ocean, each an average of 70 metres in circumference and holding 15,000 fish although the trend is toward larger pens holding twice that many fish. The average farm has eight to 10 pens.
Farmed salmon grow to market size in slightly less time than the 24 months it takes for wild salmon, mainly because they don't have to work as hard for food. (They are not given growth hormones.) An automated feeding system discharges feed pellets, containing fish meal and fish oil from ocean fish that are too small and bony for human consumption. At one time fish meal used to come from fish that was caught in the Baltic and North Seas until it was found that those fish had high levels of dioxins. "The bulk of our fish meal comes from South America now," says Rideout.
Testing for Toxins
But a small study, commissioned by the David Suzuki Foundation in Vancouver and released in February 2001, found that, even on this feed, farmed salmon had higher concentrations of PCBs and dioxin-like PCBs than wild salmon.
The CAIA points out, quite correctly, five criticisms of the study: other studies have found no difference; virtually all foods contain dioxins anyway; the levels of contaminants found were all within Health Canada guidelines; only eight salmon were tested; and the study was never peer-reviewed.
Kim Wright, an aquaculture research co-ordinator for the David Suzuki Foundation, says, "We tested the same number of fish that the government samples every year." When asked how many farmed salmon the Canadian Food Inspection Agency (CFIA) has tested recently for dioxins, PCBs and heavy metals, Stephen J. Stephen, the CFIA's national manager for aquaculture and shellfish, says that due to the complexity of the test for dioxins, "we probably didn't test [for dioxins] at all last year."
However, the CFIA does test for PCBs and heavy metals on a regular basis and, in fact, makes no distinction between wild and farmed fish when it comes to testing. Both types are examined to determine whether the contaminant levels fall within Health Canada's acceptable guidelines. Regardless of toxins, experts agree that the health benefits of eating fish far outweigh the drawbacks.
In the pink
Wild salmon eat krill, tiny shrimp-like crustaceans that give the fish its distinctive colour. Farmed salmon, which don't get krill, are salmon-coloured only because their feed contains an artifical dye. Otherwise, they'd be white. There's no evidence that the synthetic dyes - Astaxanthin and Canthaxanthin - are dangerous although there have been a few anecdotal reports involving mild allergic reactions such as rashes. The additives may even have antioxidant properties. But they're expensive and, some experts say, they mislead consumers.
"We've coloured farmed salmon to make a product that consumers are familiar with," says Richard Moccia, director of the Aquaculture Centre at the University of Guelph in Ontario. "We don't advertise the use of pigments but the industry is forthright when asked." He says that consumers are so used to coloured salmon that there's no going back now.
Aquaculture and antibiotics
When some of the fish in a pen become sick with a fish disease, such as bacterial kidney disease, all of the fish are given medicated feed. The CFIA finds that less than one per cent of salmon have antibiotic residues above the recommended level.
"It doesn't sound like much," says Sergio Paone, an environmental consultant with a PhD in chemistry, in Tofino, B.C., who has researched farmed salmon. "But in B.C. alone, one per cent would mean 500 tonnes of farmed salmon every year with antibiotic residues that are too high."
He adds that the amount of antibiotics used in aquaculture is excessive; for instance, the total amount of a single antibiotic - oxytetracycline - used for B.C. farmed salmon in 1998 was 6.4 metric tonnes. The CAIA says, however, that fish farming uses fewer antibiotics than any other livestock operation.
Scientists agree, though, that oxytetracycline passes through the fish and pollutes the ocean. Paone cites peer-reviewed studies that show that the antibiotic passes unaltered into the environment.
