Hannah Hoag

Tag: fish

  • Preventing Overfishing in the Arctic

    Preventing Overfishing in the Arctic

    The Atlantic

    A consortium of countries are meeting in Iceland, where they hope to strike a deal that protects the newly accessible ecosystem

    The Arctic Ocean has long been the least accessible of the world’s major oceans. But as climate change warms the Arctic twice as fast as anywhere else, the thick sea ice that once made it so forbidding is now beating a hasty retreat. Since 1979, when scientists began using satellites to track changes in the Arctic sea-ice expanse, its average summertime volume has dropped 75 percent from 4,000 cubic miles to 1,000 cubic miles. By September, the Arctic Ocean will have swapped nearly 4 million square miles of ice for open ocean.

    This accelerated transformation has troubled scientists, conservationists and government officials who are anxious about the fate of the fish that may live in these waters—and for the entire ecosystem itself. At the center of the Arctic Ocean is a 1.1 million square-mile “donut hole,” surrounded by Canada, the Danish territory of Greenland, Norway, Russia and the United States. The donut hole does not fall under any country’s jurisdiction, and it may well be the last unexploited fishery on Earth. According to international law, anyone could fish these newly opening high seas, if they desired, and thanks to the retreating ice, they may soon have their chance.

    → Keep reading this story over at The Atlantic

  • Acidic oceans threaten fish

    Acidic oceans threaten fish

    Stocks could suffer as seas soak up more carbon dioxide. 

    Ocean acidification looks likely to damage crucial fish stocks. Two studies published today in Nature Climate Change reveal that high carbon dioxide concentrations can cause death and organ damage in very young fish.

    The work challenges the belief that fish, unlike organisms with shells or exoskeletons made of calcium carbonate, will be safe as marine CO2 levels rise.

    Fish could be most susceptible to carbon dioxide when in the egg, or just hatched.

    Oceans act like carbon sponges, drawing CO2 from the atmosphere into the water. As the CO2 mixes with the water, it forms carbonic acid, making the water more acidic. The drop in pH removes calcite and aragonite — carbonate minerals essential for skeleton and shell formation — from the marine environment.

    This can mean that corals, algae, shellfish and molluscs have difficulty forming skeletons and shells or that their shells become pitted and dissolve.

    Flawed belief? 

    At present, atmospheric CO2 levels exceed 380 parts per million and are expected to climb throughout the century to approximately 800 p.p.m. if emissions are not kept in check. And the oceans are expected to continue to sop up the gas, dropping ocean pH by 0.4 units to about 7.7 by 2100 [2].

    However, many scientists have suggested that acidification wouldn’t be problematic for marine fish because they don’t have exoskeletons and because as adults they possess mechanisms that allow them to tolerate high concentrations of CO2.

    But a handful of studies have shown that increased CO2 levels can wreck the sense of smell of orange clown fish larvae and increase the size of the otolith — a bony organ akin to the human inner ear — in white sea bass larvae.

    Continue reading this story at Nature.

    Image: Hannes Baumann