Lindsay O’Donnell.

Seventy-three million sharks are killed every year. But you don’t eat shark-fin soup, so it’s not your problem, right? Not quite. Chances are that tuna sandwich you had for lunch is just as deadly for sharks as a killer whale that knows about tonic immobility (sorry, shark humour).

The point is that you don’t have to consume shark-fin soup to be contributing to the drastic decline of most shark populations around the world. Unsustainable fishing methods like bottom trawling, which involves a net scraping the bottom of the ocean floor and trapping everything in its nets like a bulldozer, to long line fishing, where kilometres of fishing lines with hundreds of hooks snag almost everything you can imagine, are messing with the delicate balance of the ocean’s food pyramid. The old days of sitting by a hook waiting for a bite are long gone. Modern fishing technologies that find anything hundreds of miles away are decimating ocean life like nothing that’s ever been seen before.

So why all the fuss about sharks? Well for starters, sharks are the ocean’s oldest creatures; they’ve survived every global change and evolution in the past 400 million years. These badasses have seen it all and if they’re in trouble we should be worried.

Sharks are also apex predators at the top of the ocean’s food pyramid, meaning they regulate the ocean’s ecosystems and keep other populations in manageable numbers. Nobody knows exactly what will happen if sharks go extinct. It’s possible that the phytoplankton that produces at least half of the world’s oxygen supply could increase without sharks, or we could be facing our first oxygen shortage in history. I’m not too keen to find out myself; personally I’d rather we start taking care of our oceans than risk having every living thing on the planet being asthmatic.

So what does tuna have to do with declining shark populations? Almost everything. Some tuna fisheries have recorded up to 90 percent bycatch. (Bycatch being unwanted marine life that is caught when another species is being targeted.) This number is so high because many sharks swim in the same shallow waters as commercially viable tuna.

As if tuna didn’t have enough problems—with sky high amounts of mercury in their flesh and a couple of their own species on the brink of extinction (bluefin tuna anyone?), they really don’t need the disappearance of sharks on their conscience.

So what’s the solution? Eating Oceanwise and seafood from sustainable fisheries is a start. However, when wealthy countries deplete the healthy stocks of seafood populations, less wealthy countries have no choice but to deplete the remaining fish stocks for their own food needs.

With Vancouver being so close to the water, one might argue that our economy and our fisheries need our support. Nice try, but the tuna industry is heavily subsidized by tax dollars. The true price of a can of tuna is much more than even someone with a Yaletown top floor suite can afford.

The answer isn’t an easy one but it’s effective. Demand sustainable fishing techniques from all suppliers of your seafood.

Or even better, just say no to tuna.

Lindsay O’Donnell is a cofounder of the Wake Project Society and blogs at theangryactivist.blogspot.com.