Fish Stocks Are Declining Worldwide, And Climate Change Is On The Hook

December 14, 2015,, Claire Leschin-Hoar

A fisherman shovels grey sole, a type of flounder, out of the hold of a ship at the Portland Fish Pier in Maine, September 2015. New research finds the ability of fish populations to reproduce and replenish themselves is declining across the globe. The worst news comes from the North Atlantic, where most species are declining.For anyone paying attention, it’s no secret there’s a lot of weird stuff going on in the oceans right now. We’ve got a monster El Nino looming in the Pacific. Ocean acidification is prompting hand wringing among oyster lovers. Migrating fish populations have caused tensions between countries over fishing rights. And fishermen say they’re seeing unusual patterns in fish stocks they haven’t seen before.

Researchers now have more grim news to add to the mix. An analysis published Monday in the Proceedings of the National Academy of Sciences finds that the ability of fish populations to reproduce and replenish themselves is declining across the globe.

“This, as far as we know, is the first global-scale study that documents the actual productivity of fish stocks is in decline,” says lead author Gregory L. Britten, a doctoral student at the University of California, Irvine.

Britten and some fellow researchers looked at data from a global database of 262 commercial fish stocks in dozens of large marine ecosystems across the globe. They say they’ve identified a pattern of decline in juvenile fish (young fish that have not yet reached reproductive age) that is closely tied to a decline in the amount of phytoplankton, or microalgae, in the water.

“We think it is a lack of food availability for these small fish,” says Britten. “When fish are young, their primary food is phytoplankton and microscopic animals. If they don’t find food in a matter of days, they can die.”

The worst news comes from the North Atlantic, where the vast majority of species, including Atlantic cod, European and American plaice, and sole are declining. In this case, Britten says historically heavy fishing may also play a role. Large fish, able to produce the biggest, most robust eggs, are harvested from the water. At the same time, documented declines of phytoplankton made it much more difficult for those fish stocks to bounce back when they did reproduce, despite aggressive fishery management efforts, says Britten.

When the researchers looked at plankton and fish reproduction declines in individual ecosystems, the results varied. In the North Pacific — for example, the Gulf of Alaska — there were no significant declines. But in other regions of the world, like Australia and South America, it was clear that the lack of phytoplankton was the strongest driver in diminishing fish populations.

“When you averaged globally, there was a decline,” says Britten. “Decline in phytoplankton was a factor in all species. It was a consistent variable.”

And it’s directly linked to climate change: Change in ocean temperature affects the phytoplankton population, which is impacting fish stocks, he says.

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How Will Cod React to Global Warming? Researchers Subject Fish to High CO2 Levels to Find Out

May 8th, 2014, By Eva Tallaksen,

cod in high co2Scientists in Tromso, Norway, are exposing cod broodstock to high CO2 to find out how the fish will cope as the seas get warmer, and more acidic.

“The idea is to find out, how will ocean acidification affect aquaculture and wild fish?” said Christopher Bridges, zoology professor at the university of Dusseldorf.

It is hoped larvae scooped from five tanks at Nofima’s national cod breeding center will soon yield some clues.

Each tank contained 60 cod broodstock averaging 3-5 kilos in size, exposed to different levels of temperatures and acidity. The fish spawned March and April, and their larvae, which hatched in the past two weeks, are currently being tested.

“The key aspect will be to look at the larvae’s survival rate,” said Bridges.

If global warming continues as some scientists think, the oceans’ CO2 levels could reach 1,000 to 1,200 ppm (parts per million) by 2100, up from just under 400ppm today.

That would take the seas’ pH level down to 7.8, from 8.1 today.

Most the research into the seas’ growing acidity has focused on the impact on fish eggs or larvae, or on habitats. But few have so far focused on its impact on broodstock, said Bridges.

Bridges is one of the scientists involved in the project, which is led by the publicly-funded German Bioacid initiative. Cooperating in the project are Germany’s Geomar and Alfred Wegner Institute, working in Norway under the EU FP7 support project Aquaexcel using the facilities of Nofima.

In two of the tanks, the cod were kept at normal acidity levels (400ppm), but one tank had a temperature of 5 degrees Celcius, and the other 10 degrees. In two other tanks, the fish were exposed to CO2 levels of 1,200 ppm, again with one tank at 5 degrees and the other at 10 degrees.

These four tanks all used broodstock from farmed fish, bred by Nofima’s center. A fifth tank was filled with fish from the wild, but these were caught too late to be used for the experiment.

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Study: US Methane Emissions 50% Higher Than EPA Estimate

Nov. 25 2013

51143701An oil rig pumps near the hills of California’s Wind Wolves Preserve.

A new study out on Monday says that the United States’ is emitting far more of the greenhouse gas methane than previously thought. The study, published by the National Academy of Sciences, estimates that in 2008 the US emitted 50 percent more methane gas into the atmosphere than was previously thought by the Environmental Protection Agency.

The new data indicates that methane could be a bigger challenge in combating global warming than scientists previously thought, according to the Associated Press. Here’s more from the AP:

Methane is 21 times more potent at trapping heat than carbon dioxide, the most abundant global warming gas, although it doesn’t stay in the air as long. Much of that extra methane, also called natural gas, seems to be coming from livestock, including manure, belches, and flatulence, as well as leaks from refining and drilling for oil and gas, the study says.

The new research, NBC News reports, “is based on atmospheric methane measurements taken from the top of telecommunications towers that stick more than 1,000 feet into the air as well as from airplanes.”