Ever get an uneasy feeling just before popping something in your mouth? Like, should I really be eating this?

It's a sensation that probably everyone experiences from time to time, that slight guiltiness when you spread full fat butter on a slice of bread, or use dripping to start a braise, eating chocolate saturated with palm oil, or worse, the product of child slavery, a vegetarian's sense of treachery in falling off the wagon.

Know the feeling?

I certainly do and in fact experienced it just the other day, but for none of the above reasons. It was a healthy meal of takeaway sushi that was unsettling me, the sort that comes in a little plastic box with a rubber band sealing in several different types of seafood astride mounds of wasabi smeared rice.

Glowing with ruby luminescence and cut with samurai precision were a couple of pieces of a fish that is considered the supreme embodiment of this dish by the Japanese.

The mighty bluefin tuna or maguro as it's known in Japan where they pay the utmost respect to it, right down to naming various parts of the flesh. Toro, or flesh from the belly, is the most highly prized due to its higher fat content. It's also not unheard of for a single super premium fish to fetch in excess of $100,000 or around $800 a kilo, though the more usual price is around $50 a kilo.

But even that lower price is leading to the downfall of bluefin tuna as worldwide, more and more boats chase less and less fish, forcing them onto the ever growing list of endangered marine species.

Given the huge size of the world's oceans and migratory nature of bluefin tuna, they might seem an inexhaustible resource. Past scenes of tuna boats pulling in fish as fast as they could until piled high upon their decks reinforced this image of unlimited bounty.

But it seems no one is looking to the example of the Newfoundland northern fishery, which teemed with cod and had been exploited for hundreds of years. But as fishermen got better at catching cod in the industrial age, unfortunately, the fish didn't get better at reproducing themselves and the cod population crashed in 1992, leading to the closure of the fishing ground and along the way, throwing 35,000 people out of work, the largest industrial closure in Canadian history.

The parallels in Australia are clear. It is reputed that there are more millionaires in Pt Lincoln, the tuna heart of Australia, than anywhere else in the country, made wealthy on the sleek backs of bluefin tuna.

It is here, after the catches of large tuna declined, a new method was pioneered to catch huge shoals of smaller fish, pen them in nets which are then dragged to shore and set up as fish farms. This led to a recent conversation with a chef who proudly told me he only used sustainable fish and that included bluefin tuna as it was farmed.

Let me say right here, wild caught fish is not farmed in any traditional sense, just caught and fattened and continues to deplete the oceans stocks to the point where bluefin tuna are now critically endangered.

So it was heartening to read of Richard Auffrey of the blog Passionate Foodie, who called out to Alton Brown over his involvement with bluefin tuna on the hit show Iron Chef America. To his credit, Alton responded and bluefin tuna has now been banned from the show, a small win for the fish.

In my own case, I've decided to no longer eat bluefin tuna. It just doesn't feel any good knowing that I'm helping to destroy a species of fish for a little oral gratification. In turn, I'm asking you to think about the issue too.

Don't kid yourself that because the fish is already dead, it's okay to eat, because that means a fisherman will go out and catch another and that will be dead too. Don't fall for the sustainable farmed fish argument either unless scientists actually work out how to breed tuna, until then, they are all still wild fish.

To this date, the Newfoundland fishery hasn't recovered, some 18 years on. Don't let it happen to the bluefin tuna too.