Saving Seafood

Ocean acidification threatens future of aquaculture, shellfish industries

October 29, 2015 — In seawater tanks in a refrigerated room at the Darling Marine Center, the baby mussels are thriving.

Two months ago they were near-invisible larvae, swimming around in the tanks. Now tens of thousands of the tiny mollusks, each just a few millimeters long, have attached themselves to the different kinds of rope scientists have been testing here, and are eating the lab’s stock of algal food at an impressive clip.

Mick Devin, the lab manager at this University of Maine marine research facility, has been overseeing this experiment, part of an effort to master the art of hatching mussels, something mussel farmers – who grow their product on lines hanging in seawater – have never previously needed to do.

“Mussel farmers have been able to just throw their lines out and collect all the larvae they want from nature,” Devin says. “But mussel populations are down drastically in this state, so that may not be working so well now.” Hatcheries, he expects, may have to step up in the not-too-distant future.

Mussels have been vanishing from stretches of coastline where they once were ubiquitous, and scientists remain uncertain as to why. Green crabs, whose population exploded after an “ocean heat wave” in 2012, may have stripped many sections clean. But warmer water and increased rainfall – both problems expected to grow in Maine as a result of global climate change – may be creating a far worse problem: an acid sea.

“We know this affects larval development in bivalves, (and) chances are it will result in decreased numbers, whether it’s a natural population on a bed or one in a farm,” says Paul Rawson of the University of Maine’s School of Marine Sciences, who is in charge of the research. “We need to make sure the technology is in place so the farms will have a reliable source of seed.”

The world’s oceans are turning more acidic. Since the Industrial Revolution, carbon dioxide levels in the atmosphere have grown by more than 70 percent and now stand at the highest level in at least 800,000 years. As the oceans absorb additional CO2, they’ve become 30 percent more acidic over this period. By 2050, scientists estimate surface pH levels will be lower – that is, more acidic – than at any time in several million years and by 2100 more acidic than any time in the past 300 million years – two or three times more so than today.

Read the full story at Portland Press Herald

Absurd Creature of the Week: This Crafty Fish Turns Mussels Into Its Surrogate Parents

October 23, 2015 — Last week I wrote a little ditty about North America’s lampsilis mussels, which do unbelievable impressions of fish. And why would they? So that real fish attack them, busting loose clouds of mussel larvae that infiltrate the attackers’ gills. Here the larvae clamp onto the filaments and suck out nutrition, developing in safety until they drop out of their host. This, as you can imagine, is bad for the fish, to the point where it can kill them.

Lampsilis has the most highfalutin way of infesting fish with their larvae, but freshwater mussels the world over do it too—simply by releasing the young into the water column. There’s one group of fishes in Europe and Asia, though, that won’t suffer such parasitization without retaliation: the bitterlings. These guys flip mussels’ reproductive strategy back on them. Using a tube-like structure, the female fish inserts her eggs into a mussel’s gills, then the male fires his sperm in as well. The fertilized eggs get a nice little home in the host. The host mostly just gets embarrassed.

So let us explore the strange game that is different kinds of parasitic river critters trying to impregnate each other with their offspring.

Typically fish reproduction is about as basic as it gets in the animal kingdom. Males and females get near each other, then dump their sperm and eggs into the water. That’s it. The problem with that, though, is it opens the young up to all kinds of problems, particularly predation. Only a fraction will make it. The rest will end up in stomachs.

For the bitterling, this won’t do. Its reproduction begins with good mussels, and it’s up to the male to find them, preferably large hosts with more room to hold the young. When he chooses a victim, or even several in a given area, he posts up. Should rival males take an interest in his property, his coloration intensifies as he head-butts his foes for control of the territory.

Read the full story at Wired

Where have Maine’s mussels gone?

CASCO BAY, Maine  — August 30, 2015 — The survey map in Ann Thayer’s hand showed fat red splotches that wrapped around two-thirds of Bangs Island’s shoreline, meaning that the intertidal zone – the zone between the high and low water marks – was supposed to be densely packed with mussel beds. The tide was nearly three hours past high, leaving plenty of rockweed exposed.

Thayer began systematically flipping over the weed, looking for mussels, aka Mytilus edulis, attached to the rock below.

“Nothing,” she said. She said this over and over.

By the time she got back into her dinghy to row back to her Boston Whaler, she’d found only two mussels. Two where surveys from the 1970s and 1990s indicated there should be thousands, mollusks wedged into almost every nook and cranny in the rocks, the blue-hued shellfish nearly as commonplace as the barnacles living on their shells.

Thayer, who serves on the board of directors of Friends of Casco Bay, was not surprised by her findings.

Read the full story from the Portland Press Herald