A Taiwanese longline fishing vessel, just one of thousands of tuna boats fishing the Pacific Ocean.

Out in the Pacific Ocean thousands of fishing vessels are working around the clock to pull tuna out of the sea as fast as they can.

It's a global business, and it's big business, turning over billions of dollars a year, with millions of people employed in catching the tuna that millions of others rely on for sustenance and survival.

Unfortunately, the way these businesses operate is putting the whole system at risk. They are out of control. Pillaging the Pacific Ocean , they are taking too many fish , breaking laws and international agreements , and raiding the waters of small coastal nations .

Recent stories of labor abuse , terrible bullying , slavery and human trafficking are exposing serious problems in global fisheries. Similar stories -- too many to ignore -- are starting to emerge from the tuna fleet.

Longliners catching albacore for the canned tuna markets of the West can be like floating sweatshops, taking young men desperate for work away from their families, locking them into contracts that can last for years, and saddling them with debt if they try to break those contracts early.

Out on the high seas, with no means of escape, it must seem to some of these young fishermen as if they are serving a prison sentence. And with less than 1 percent percent of fishing activity by longline fleets witnessed by on board independent observers in the Western Central Pacific, there is no one to turn to and nowhere to go. It is the perfect environment for exploitation -- a captive workforce.

Last week, Greenpeace released a series of videos linking bullying and labor abuse to Pacific tuna boats. The stories of violence and exploitation we have heard from tuna fishermen are heartbreaking.

Adding to this bleak picture, many longliners transship their catches while still at sea to refrigerated cargo ships, which means the fishing boats can stay at sea for years.

High-seas transshipping is an enabler of both human rights and environmental abuses. It's the fisheries equivalent of money laundering, where illegal or "dirty" fish can enter the supply chain and become impossible to differentiate from the "clean."

It also means that Pacific nations miss out on the revenue and jobs that would come with processing and packing those fish ashore. Pacific purse seine fleets are banned from transshipping catches at sea . The practice should now be made illegal for tuna longlining ships as well.

While the costs of human rights abuse and environmental crime cannot be compared, they are both driven by the greed of an industry that is out of control. If we fix one, we fix the other.

Like too many other industries, tuna is dominated by big business working in the interests of the few, using cheap or free labor, and catching fish in the high seas commons that should belong to all of us. If we fail to act now, fishermen will continue to be exploited by an industry that is degrading tuna stocks and harming our oceans.

For tuna, at least, there is an easy remedy. While stocks of bluefin and bigeye tuna are in serious trouble, albacore and skipjack are at the point where, if changes are made to fishing practices today, we can ensure there are enough fish for tomorrow. Fished sustainably, tuna can continue to feed and employ people across the globe, and protect the coastal communities who rely on them for survival.

It's not an impossible vision. The last thing tuna-eaters want is the bitter taste of worker abuse or environmental devastation in their tuna salads or sashimi. We know that because Greenpeace's tuna guides are among our most popular information resources. People often find it shocking when they learn of the ocean and human destruction that goes into a can of tuna.

As consumers, we can give the big corporations a push in the right direction and overcome their resistance to change. By choosing to buy sustainable tuna we can tell the industry that we are not prepared to support the destruction of our oceans or the exploitation of workers.

As a form of protest it's as easy as it gets. Every time a shopper reaches for a can of sustainably sourced tuna on a supermarket shelf it sends a message to the fishing industry that it's time to change.

Tuna fisheries are global fisheries. If we can get them right we can create a model for the oceans; to feed and employ people and protect the health of our planet.

Right now the Rainbow Warrior is sailing the Pacific Ocean and its crew is focused on putting the tuna industry in the spotlight. But back on land we can all play an important role in helping to create change at sea.

Next time you visit a supermarket or a sushi bar, consider using the power of your wallet to tell the tuna industry that there is no place for ocean devastation and human rights abuse on our plates or in our lunchboxes .

Kumi Naidoo is the Executive Director of Greenpeace International.