There's a tendency, outside my science world at least, to talk about 'tuna' as if it was one species of fish. In fact tuna is a generic name for a whole bunch of tuna and mackerel species.

As well as the main commercial species of skipjack, yellowfin, bigeye, albacore, and three species of bluefin, there are other related species like longtail tuna, bonito and Spanish mackerel. In fact, skipjack isn't even a true tuna, it's a kind of mackerel!

The different species have different growth and reproduction rates, abundance levels, and habitats. They are fished by different fleets using different methods and have different market values, which makes managing tuna fisheries, and writing about them, a complicated matter. Some tuna companies take advantage of this complication to mask unethical and unsustainable behaviour.

I'm in Pohnpei, Micronesia, at the Science Committee meeting for the Western and Central Pacific Fisheries Commission (WCPFC), which manages the tuna and billfish fisheries in the region. A big focus of this year's meeting is the problems managing the South Pacific albacore fisheries.

Albacore is temperate, so while its tropical tuna cousins like to hang around the equator, albacore prefers cooler waters further south or north. Which makes albacore the most important tuna species for the domestic longline fisheries of the South Pacific Island Countries of American Samoa, Cook Islands, Fiji, New Caledonia, Samoa and Vanuatu, and the troll fisheries further south around New Zealand.

Albacore is far less abundant – probably over ten times less abundant than skipjack tuna. In the 2014 catch figures, just 83,000 tonnes of South Pacific albacore were caught compared to a massive 1.9 million tonnes of skipjack.

This week, scientists are presenting a new stock assessment showing the South Pacific albacore population has been fished down to about 40% of its original size. It's not yet a dangerous level for albacore, but it's a big problem for the fisheries. With a shrinking population, the already less abundant albacore is getting harder to find.

Because it takes longer to find and catch albacore, the costs of running a longline vessel – primarily labour and fuel – are now equal to or higher than the price fishermen get for their catches. Many Pacific Island longline fishing vessels barely break even, and some are running at a loss.

One of the thousands of longliners fishing the Pacific Ocean for tuna, spotted today by the Rainbow Warrior. © Mark Smith / GreenpeaceOne of the thousands of longliners fishing the Pacific Ocean for tuna, spotted today by the Rainbow Warrior.

Representatives from Samoa told me today that their fleets had their lowest albacore catch for five years, and some of their larger vessels had to tie up in January. Their smaller vessels have been able to keep going, mainly because they can sell their fish locally at a higher price than the export rate, but most are currently running at a loss.

Fleets with heavy government subsidy are able to continue to fish for albacore. Some unscrupulous vessel owners take advantage of the fact longliners operate out-of-sight on the high seas and cut labour costs. There is increasing evidence that fishing crews on high seas tuna vessels suffer from poor pay and harsh working conditions and Greenpeace recently release a series of videos documenting labour abuse in the distant water tuna fleets.

Government subsidies, exploiting crew, and putting local fisheries out of business, are signs of an unsustainable global industry that's out of control. If we want albacore fisheries to continue to feed and employ people we need to make changes and we need to make them now.

According to science and economic studies being presented this week, we need to let the South Pacific albacore stock double in size to ensure that fishing fleets remain profitable. If we don't, then Pacific Islanders and the crews of high sea longline fleets will suffer the consequences.

The Rainbow Warrior is sailing through the Pacific tuna grounds right now. We're telling the industry it's time to change. Check out our new website:, or follow the conversation at #changetuna.

Dr. Cat DoreyDr Cat Dorey is the Science Advisor for the Greenpeace tuna project, and is currently in Pohnpei Micronesia – a small Island in the Pacific – discussing the latest research on Pacific tunas fisheries.