My fingers grip the ledge at the stern of the 45-foot fishing boat.

As the eight- to 10-foot-high waves crash onto the deck, I feel the water make its way into the gaps between the buttons of my oil slicker, up my sleeves and into my too-large rubber boots. I squint through the saltwater spray at the rolling Atlantic Ocean off the coast of P.E.I.

Unlike many tourists to Canada’s Maritimes, I’m not here to whale-watch. No, I’m going to feed the Giants — also known as bluefin tuna.

“Whales are boring,” Captain Kenny McRae tells me. “They don’t put on a show like [bluefin] tuna do.”

On a good day, bluefin tuna come right up to the fishing boat to feast on the mackerel thrown to them, their blue-black skin shimmering in the sunshine. A top predator in the marine food chain, the torpedo-shaped fish is one of the fastest and most powerful on the planet, capable of reaching speeds of up to 70 kilometres per hour. Now imagine all that speed in a body weighing as much as an adult moose — the largest bluefin ever recorded weighed in at 679 kilograms — hurtling past your boat.

But the fish is more than a biological wonder and an unusual tourist attraction. It’s also a highly sought-after delicacy in Japan’s sushi restaurants, which has made it a potential goldmine for the fishermen lucky enough to be licenced to catch one — and a species struggling for survival.

While western Atlantic fishermen had little interest in bluefin tuna before the 1950s, demand grew in the 1960s, and the species, which migrates north from the Gulf of Mexico, became severely overfished. To address the species’ increasingly dire state, a group of countries including Canada founded the International Commission for the Conservation of Atlantic Tunas (ICCAT) in 1969, and the regulatory body eventually introduced a quota system. Despite the quota, the bluefin tuna hasn’t yet recovered. In fact, the species has declined 69 per cent in the past 45 years.

In 2011, the Committee on the Status of Endangered Wildlife in Canada recommended that the federal government list the species as endangered under the Species At Risk Act. To do so would be to put an end to an industry estimated by the Department of Fisheries and Oceans to be worth about $10 million annually.

The government has not yet made a decision on the species’ status. But last November, much to the chagrin of Canadian marine scientists, the government pushed the ICCAT for an increase in the annual quota.

For now, fishing the bluefin tuna remains highly regulated. The quota for those with licences in P.E.I. is just one per year. Kenny McRae caught his fish of the year the day before our outing.

“It was a nice fish. It was fat. That’s what you want.”

But it wasn’t quite like McRae’s biggest. The big cash-in for McRae came in 1994 when he caught a fish weighing more than 360 kilos gutted. It went for $27,000.

On the Japanese market, the profitability of a fish ultimately depends on the colour of its meat — the ideal is a strawberry pink — and the volatile market price. In 2013, a famous sushi restaurateur broke the world record by spending the equivalent of $1.6 million on a single fish. This year, however, the market price plummeted. The top fish sold for less than $80,000, a 95 per cent drop in price.

After meeting the annual quota, it’s the tourists like myself, opting for a different kind of adventure, who bring in some profits for the fishermen.

And it is an adventure. Our boat continues to rise and fall in the waves, and just as I’m starting to wonder whether I should have taken McRae seriously when he asked if I got seasick, he calls it — the wind is too strong, we’re turning around. We pause in the much calmer water near the tip of the island to watch a colony of seals bob in and out of the water before heading back to the dock.

Given the uncertainty of Canada’s bluefin tuna fishing industry both in terms of the market price and the species’ status under the Species At Risk Act, tuna-watching tourism could one day be the only bluefin tuna-related income for P.E.I. fishermen like McRae.

As for me, I’ll just have to watch the YouTube videos of the powerful and controversial fish instead.