Archive for April, 2012

Fishing for the Halibut

Thursday, April 26th, 2012

The Atlantic Halibut is an extraordinary fish, once one of the world’s largest. Old reports suggest males could have grown to 700 pounds and 15 feet (320 kg and 4.7 m). Long lived, slow growing, late maturing, and easily caught by bottom trawls and long lines, they were quickly overfished once people acquired a taste for them. Now not many are left, and the species is labelled Vulnerable or Endangered, depending on the agency assessing them.

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Halibut are bottom dwelling flatfish that prey on other fish as well as crustaceans. This is the Pacific halibut, which has been fished sustainably. Atlantic halibut are too rare to be able to photograph in the wild like this (marinesciencetoday.com)

Fishing along the New England coast and on the offshore fishing banks remains a disaster. Collapsed stocks like halibut recover very slowly, if at all, and even cod, which ought to be more resilient, have failed to show signs of recovery. Quotas are small and getting smaller, and so are fishing fleets.

An 8 foot, 444 pound Atlantic halibut caught off Norway in 2008, no doubt one of the last of this size (tiptheplanet.com)

Whole Foods Market is going to sell only the fish species considered sustainable by the Monterrey Bay Aquarium and the Blue Ocean Institute, and that eliminates the Atlantic halibut – as it should. Plenty of other markets exist, but it sets a good example. We simply should not be eating any wild caught Atlantic halibut.

A very new method of aquaculture involves submerged, ‘deepwater’ AquaPod Net Pens – geodesic spherical enclosures that have been used for cod, salmon, and other species, but not yet for halibut.

Now there is a proposal to farm Atlantic halibut in a bay on the central coast of Maine, starting with one Aquapod about 30 ft in diameter, tethered to the bottom by an 18,000 pound anchor, able to spin out with tide in a 150 ft radius.

An AquaPod Net Pen is lifted by crane onto a barge and then later into deeper water offshore (oceanfarmtech.net)

The halibut would be raised in a hatchery from egg to settled stage, and then moved to the AquaPod, fed fish pellets designed for halibut, monitored to prevent over-feeding, and grown rapidly to marketable size.

An AquaPod is neutrally buoyant, can be rotated to clean, and can be partly emerged or totally submerged depending on ocean conditions (ecofriend.com)

But will it work? There are legitimate environmental concerns about the impact of uneaten food and feces on the existing bottom community, and very careful monitoring is essential. Though the Aquapod would be set in the deeper water where the dozen or more lobstermen who work the bay don’t set many of their thousands of lobster pots, other commercial fishing would be blocked.

Each year farmed fish make up more of the total fish production

Some halibut farming will be helpful. Done right, done carefully, it should work. But AquaPod culture of halibut is very much an experiment, and it needs to occur where other fishermen are not affected, and where coastal communities are sparse. A bay that is saturated with lobsterpots, cottages, summer residents and their boats is not the place for this experiment.

Soon more half of the world’s marketed fish will be farmed – a reflection not just of the collapse of wild caught fisheries but also of the growth of farming.

So let’s farm halibut. Let’s try to farm them in AquaPods. But let’s do it carefully, in places where other users are least affected, and where experimental failure has the least impact.

The Acidification of Oysters

Monday, April 23rd, 2012

Maybe you read about this recently. It seems to me to be quite amazing.

A die-off of oyster larvae at the Whiskey Creek Shellfish Hatchery on the Oregon coast has been correlated with – and almost certainly caused by – a small increase in the acidity of the sea water the larvae were exposed to in their first 24 hrs.

Oyster larvae need critical levels of CaCO3 for their shells to develop, and these levels drop as CO2 levels in the water increase.

Oyster larvae (marineticsinc.com)

The report was published in April in the journal Limnology and Oceanography by three scientists (Richard Feely, Alan Barton and Burke Hales). Then Jeff Barnard, Environmental Writer for the Associated Press, published a summary of the study, and pretty well everyone took notice. When I Googled ‘oyster larvae dying’, most of the first 300 hits were copies of his article republished by American and global news websites.

Oyster life cycle (scienceinthetriangle.org)

All the reports, not just AP’s, emphasize that this is some of the first solid evidence of the potential impact of ocean acidification on a valuable fishery, though in fact oyster growers have been concerned about the threat of acidification for some years.

Anything that has a calcareous skeleton is sensitive to increased acidity (noaa.gov)

The event is worrisome, of course, for ocean acidification will continue for many decades, even once (or if?) we stop the increase in atmospheric CO2. Now we know that a very small change in ocean acidity can have a large impact on a sensitive species.

As atmospheric levels of CO2 increase, so do levels in the ocean, resulting in increasing ocean acidity (e360.yale.edu)

But what’s unexpected is the attention the journal publication and its AP description have received. It should signal to our political leaders in North America that in fact people really are worried about the accelerating effects of global warming.

How much evidence is needed? The death of some oyster larvae won’t change the beliefs of most of the US Congress, but it ought to.

It also won’t effect the politics and business of oil that dominates the Canadian economy, but it should.

They say we get the leaders that we deserve, but we don’t deserve this.

The die-off of the oyster larvae cannot be shrugged off as irrelevant or insignificant.

So we are warned.
Again.