Fishing for salmon answers

Here’s your weekly Science Matters column by David Suzuki with Faisal Moola.

Fishing for salmon answers

Most of our food, whether plant or animal, comes from farms. A notable
exception is fish and seafood, much of which is caught from wild ocean
stocks. That’s starting to change, though, as aquaculture plays an
increasingly important role in the global food supply.

In many respects, that’s good news, especially when wild
fisheries are being harvested at or beyond a sustainable limit, and
pollution and global warming, among other threats, are decimating wild
fish stocks. When the aquaculture practices themselves start harming
the wild fish, though, we must question whether or not the costs of the
way we are farming outweigh the benefits.

Many aquaculture operations are environmentally sound, especially
those that separate farmed fish from wild fish, such as the contained
tanks and pond systems used to farm species such as tilapia and turbot.
As well, many types of shellfish are farmed in ways that do not harm
the environment.

Yes, you heard me right: some types of aquaculture are okay. And yes, I eat some farmed seafood.

But current salmon-farming practices are a different story. We’ve seen
a lot of headlines lately about the damage done by salmon farms, here
in Canada and in other parts of the world. The scientific evidence is
strong and growing, for example, that sea lice from salmon farms in
B.C. are causing severe damage to wild salmon stocks.

Sea lice are natural parasites that feed on salmon, and are
especially harmful to juvenile salmon, which don’t yet have scales to
protect them and which aren’t normally exposed to sea lice in large
concentrations. Sea lice multiply on salmon farms and attach themselves
to juvenile salmon as they pass the farms on their way out to sea.
Using drugs to control the lice isn’t the answer, as the drugs come
with their own environmental risks. And at best it is only a short-term
solution as sea lice are already developing resistance to the main
drugs used to control them.

Research has demonstrated similar situations in other salmon-farming
regions like Scotland, Ireland, Norway, and Chile. Here in North
America, a series of peer-reviewed scientific studies published in
reputable journals such as Science and the Proceedings of the National
Academies of Science has shown that sea lice can cause serious harm to
wild salmon, including putting some stocks of pink and chum salmon at
risk of extinction.

Wild salmon do not need additional threats to their survival. To put
the issue in perspective, the West Coast of Vancouver Island once
boasted 1,200 stocks. Now, some 718 – more than half – are extinct, at
moderate risk of extinction, or considered stocks of special concern.
At least 142 Pacific salmon populations have vanished forever.

Given the scientific evidence and the social, economic, and
biological value of salmon, it is reasonable to expect change in the
way things are done. Unfortunately, some people argue that the lack of
100 per cent proof means nothing should change. But scientific research
rarely gives us such smoking guns. Nature is just too complex to even
expect such a result. Science is a process of demonstrating the weight
of evidence. Studies build on each other, eliminate alternative
explanations, and test parallel ideas that help get to the most likely
answer. In the process, other scientists have ways to challenge each
other and test competing ideas. At a certain point, you have a solid
reason to believe a given explanation is worthwhile. When something is
as important as wild salmon, a strong weight of evidence justifies
corrective action.

So what can we do? As a temporary solution, the salmon farms should
be fallowed (removing the farmed fish for a period) while the juvenile
fish pass by on their way out to sea. But the best solution would be to
raise salmon in closed tanks that keep the farmed fish separate from
the wild fish and their environments. Consumers should urge grocery
stores and restaurants to sell only environmentally sound seafood
products and should avoid buying products that are not.

Some people argue that it would cost too much to move to closed
system aquaculture, or even to fallow farms during juvenile migration
periods. But salmon can’t be seen just as a food source for people, and
the costs of running any agricultural operation can’t be seen to just
encompass the money required to build and run the farms. Wild salmon
are a critical part of ocean, river, lake, and forest ecosystems. They
provide food for everything from whales to eagles to bears, and even
help fertilize the forests along the shores, rivers, and lakes where
they live and spawn.

Yes, everything is interconnected. If the wild salmon dwindle and
die, next come whales, bears, and our forests… And where will that
leave us?