http://www.digitaljournal.com/news/environment/world-s-tuna-and-mackerel-populations-suffer-drastic-74-decline/article/444048

World's tuna and mackerel populations suffer drastic 74% decline

Posted Sep 17, 2015 by Megan Hamilton
Tuna and mackerel populations have suffered a drastic 74 percent decline within the last 40 years, researchers have found. The World Wildlife Fund warns that if we don't act quickly, we face losing species that are critical to human food security.
Bluefin tuna tested for cesium levels from Fukushima.
Bluefin tuna tested for cesium levels from Fukushima.
Video screen capture
Research conducted by the WWF and the Zoological Society of London shows that fish populations in the scombridae family — including bonito, plummeted by 74 percent between 1970 and 2012, far higher than a decline of 49 percent of 1,234 ocean species during the same time period, The Guardian reports.
To save these critical species, overfishing and other threats to marine life must be stopped, the WWF reports.
"This is catastrophic," said Louise Heaps, the WWF UK chief advisor on marine policy. "We are destroying vital food sources, and the ecology of our oceans."
For the past several years, attention been focused on species like bluefin tuna, now perilously close to extinction, but other close relatives frequently found on menus or in cans, like yellowtail tuna and albacore, are also becoming considerably more scarce. Skipjack, which is also canned, is showing "a surprising degree of resilience," Heaps says. She is one of the authors of the Living Blue Planet report, published on Wednesday.
Every year the WWF and the ZSL publish the Living Blue Planet report. It's an analysis of a database called the Living Planet Index, which tracks changes in the size of animal populations worldwide — including 5,829 distinct populations of 1,234 marine species in the aforementioned time frame, Quartz reports.
This year, the WWF and ZSL published an emergency edition of the report.
"We urgently published this report to provide the most current picture of the state of the ocean," Marco Lambertini, Director General of WWF International said in a press release. "In the space of a single generation, human activity has severely damaged the ocean by catching fish faster than they can reproduce while also destroying their nurseries. Profound changes are needed to ensure abundant ocean life for future generations."
He also said:
"We are in a race to catch fish that could end with people starved of a vital food source and an essential economic engine. Overfishing, destruction of marine habitats and climate change have dire consequences for the entire human population, with the poorest communities that rely on the sea getting hit fastest and hardest. The collapse of ocean ecosystems could trigger serious economic decline — and undermine our fight to eradicate poverty and malnutrition," said Lambertini.
It's not just tuna and their relatives that are suffering, ZME Science reports.
Populations of sea cucumbers, a delicacy in Asia, have fallen precipitously by 98 percent in the Galapagos and 94 percent in the Egyptian Red Sea. Leatherback sea turtle populations have also plummeted.
ZME Science notes that overfishing isn't the only threat. Pollution, the effects of climate change, and plastic garbage that we litter the ocean with also take a heavy toll, especially as it builds up in the digestive tracts of fish and other marine species. The effects of climate change are disastrous, and one of the worst complications is ocean acidification. As we spew more and more carbon dioxide, some of it is trapped in the ocean, and this increases the acidity of the water.
"I am terrified about acidification," Heaps said, per the Guardian. "That situation is looking very bleak. We were taught in the 1980s that the solution to pollution is dilution, but that suggests the oceans have an infinite capacity to absorb our pollution. That is not true, and we have reached the capacity now."
Corals off Ross Island.
Corals off Ross Island.
Screen grab
The world's coral reefs could be extinct by 2050, she says, if we keep doing what we're doing. She noted that the evidence of the effects of acidification, which damages tiny marine creatures that depend on calcium to build their shells and other organs, could be found from the Antarctic to the U.S. west coast.
 The Great Barrier Reef in Australia already has been affected by ocean warming and acidification.
"The Great Barrier Reef in Australia already has been affected by ocean warming and acidification."
Rau et al.
While overfishing is a global problem, the Pacific is particularly worrisome, because the Chinese, Japanese, and Korean fleets are among the world's largest, and are greater in size and fishing capacity than Europe's.
Increasingly, Chinese fishermen are expanding their reach and fishing in other waters. Shark populations have been decimated as a result of shark-finning to make the Asian delicacy shark-fin soup. If nothing is done, it's predicted that a quarter of all shark species will become extinct in a decade, the Guardian reports.
There are solutions, Heaps says.
"It's not all doom-and-gloom. There are choices we can make. But it is urgent."
We can manage overfishing by using better governance. In the North Sea, cod stocks have recovered, she notes, so better management can work. She also urges governments to adopt sustainable development goals as proposed by the United Nations and to include provisions for protecting marine life, which will be part of the agenda at the UN general assembly later this month.
Heaps is also urging people to only eat fish that is certified as sustainable by the Marine Stewardship Council. Using a range of criteria, this council examines fisheries to make sure they are being properly managed. More and more fisheries have been accredited by the MSC, and currently about half of the world's white fish stocks are certified, and this includes several in the North Sea, the Guardian reports.
Another idea is to increase partnerships between fishing fleets in the private sector and governments as a way to conserve fish stocks.
"We need to keep [fishermen] on board, because they must see that good governance is in their interests," Heaps said.
Fisheries in Japan, however, appear to be quite reticent, when it comes to protecting fish stocks. Earlier this month, at a meeting in Sapporo, northern Japan, between countries that monitor stocks in most of the Pacific Ocean, no progress was made towards helping fish populations recover from decades of overfishing.
Last year, faced with the collapse of bluefin populations, members of the Western and Central Pacific Fisheries Commission decided to reduce by half the catch of tuna weighing less than 30kg from its average level in 2002 — 2004. Conservation groups had, however, called for a moratorium to give stocks a chance to recover, the Guardian reports.
But if we are to save the bluefin tuna population, urgent action is necessary, campaigners say. In 2012, populations of this fish were estimated to have fallen by 96 percent from unfished levels during nearly a century of overfishing.
"Unfortunately, the only outcome of this week's meeting is a guarantee that the Pacific bluefin tuna population will decline even further because of the continued inaction of 10 governments responsible for the management of this species," said Amanda Nickson, director of the Pew Charitable Trusts, per the Guardian.
She upbraided Japan for not supporting more conservation measures that would allow the fish, which spawn millions of eggs every year, to recovery quickly.
Japan scarfs up about 80 percent of the global bluefin catch, where it is served raw as sashimi and sushi. That, along with skyrocketing demand in China and other parts of Asia are hastening the demise of the Pacific bluefin tuna. Last year this prompted the International Union for Conservation of Nature to move the fish from the category of "least concern" to "vulnerable" on its red list of threatened species.
According to the IUCN, estimates show that the Pacific bluefin population has dropped by 19 percent to 33 percent over the past 22 years, mainly to satisfy demand in Asia. Even with full implementation of existing conservation measures, analysis shows that Pacific bluefin stocks will continue to drop through 2018, the IUCN found.
The organization also predicts that during the next 10 years, there is a one in three chance that the Pacific bluefin population will fall to the lowest level ever recorded, the Guardian reports.
If we can't get governments to agree on these crucial fish stocks, the future for the world's oceans looks very stark.