4 Dirty Secrets Hiding In Your Tuna Can

A turtle caught on a Korean longline.

This is the latest installment in Casson Trenor's monthly column, 4 Oceans, about protecting our fisheries and ocean health through sustainable seafood.

Seafood isn't only sold in the seafood section. Americans buy a tremendous amount of seafood from the shelves of our local grocer rather than from the freezers, including one particular item found in everything from sandwiches and casseroles to salads: tuna fish.

For decades, tuna was the most widely consumed seafood product in the United States. Although it has recently lost pole position to farmed shrimp, it is still massively popular, and even though it's in a can, it is still fish, and thus merits scrutiny in terms of sustainable practices -- or, in this case, the total lack thereof.

Here's the issue: catching tuna in a manner that keeps the price hovering around $1-$2 per can is difficult. It's a challenging process for a number of reasons, not least of which is that most species of tuna are constantly on the move across the vastness of the open ocean. Chasing these schools around is a time- and resource-intensive process -- especially with oil prices on the perpetual upswing -- but the tuna industry has found a way to cut some pretty significant corners. Unfortunately, this has led to any number of nasty consequences, and those smiling bumblebees and luxuriating mermaids on the tuna cans at your neighborhood grocery store have done a great job covering them up... until now. 

The tuna industry has a dirty little secret -- actually, it has four of them.

1. Fish Aggregating Devices

Fish aggregating devices (aka FADs) are floating objects that tuna vessels cast adrift in the open ocean. They are generally attached to a radio beacon and can relay their position back to a given tuna boat. FADs work because fish in the open ocean find random flotsam absolutely captivating. Small plants and polyps anchor themselves to the physical body of the FAD, small fish use it as a hiding place, and larger animals flock to it as a source of shade and as a fertile hunting ground. After a few weeks at sea, a FAD can develop an entire ecosystem around it, which is wiped out entirely when the tuna boat returns and scoops the whole thing up in a seine net.

The problem is that FADs don't just attract the target species of tuna (usually skipjack). They are similarly mesmerizing to sharks, billfish and other animals -- most notably juvenile yellowfin and bigeye tuna -- that come swimming by wondering what all the fuss is about.

By then, it's generally too late.

FADs increase bycatch in the skipjack tuna industry by between 500 percent and 1000 percent when compared to nets set on free-swimming schools (FAD-free seining). To make matters worse, between 15 percent and 20 percent of the total catch of a FAD-associated skipjack seine is actually juvenile yellowfin and bigeye -- two species of tuna that are in serious trouble and cannot afford to have their young purloined before they ever have a chance to breed. The total content of bigeye and yellowfin in FAD-free skipjack seines is less than 1 percent.

I'll put this plainly -- if we don't stop using FADs, we will run out of yellowfin and bigeye tuna because we will kill all of the juveniles.

Rule #1 for sustainable canned tuna: When shopping for "light" tuna, buy pole-and-line or FAD-free seined skipjack.

2. Longlines

Cans of "white" tuna contain albacore, a temperate tuna species that is only popular in canned form in North America. Albacore isn't caught with purse seines as often as it is caught on longlines -- an equally destructive practice that incurs a tremendous amount of bycatch. Longlines are just that -- long lines set by fishing vessels that stretch from buoy to buoy across the open ocean, sometimes for multiple miles at a stretch. Every few yards, a long lead ending in a baited hook dangles from the main line. When the ship circles back to reel in the longline and assess its catch, it contains far more than albacore tuna. This indiscriminate fishing method is one of the greatest killers of turtles (which get hooked nibbling on the bait, can't return to the surface to breathe, and drown), albatross and other seabirds (which dive on the glinting hooks thinking they're fish and are subsequently snagged), and other non-targeted animals.