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Archive for the ‘fisheries’ Category

chinook.jpg

More evidence that everything in the universe, or at least the Pacific, really is connected. By odds too remote to be calculated, a New Zealand biologist discovered a rice-sized ID chip in the stomach of a sooty shearwater chick.

The chip traced to a chinook salmon tagged two years ago on the Columbia River, more than 7,000 miles away.

The biologists have been making the mental leaps ever since. Shearwater chicks are flightless and don’t even get in the water until after they fledge. The bird’s parent must have eaten the salmon, then regurgitated the chip into the chick along with a meal. But chinook salmon are big – way bigger than a shearwater (if there’s any justice in the world, there should be some chinook salmon swimming around right now with shearwater tags in their bellies).

Anyway, that means the shearwater must have plucked the tagged chinook out of the water back when the fish was beak sized – and carried the chip since then. That’s imaginable, since all birds have a crop – a sort of mechanical stomach where they store hard objects. It’s what they have instead of teeth. The chip could have lodged in there and then just come back out again.

And shearwaters are famous travelers. Just last year, in fact, a team of biologists made headlines when they established that sooty shearwaters take a 40,000 mile, figure-8 loop around the Pacific every year chasing an endless summer of food.

Oh, and the biologists were from the University of California, Santa Cruz. See what I mean about everything being connected?

Thanks to the KSJ Tracker for picking this one up, and nice work by the Seattle Times running this great piece of news. Image: Jeffrey Rich.

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tilapia.jpg

File under win-win: research in Kenya shows that by raising tilapia, locals can reduce the population of a malaria-carrying mosquito (by a whopping 94%), then harvest the fish for the dinner table.

Spurred by the growing incidence of pesticide resistance among mosquitoes, the researchers began looking for nonchemical ways to kill the mosquitoes’ buzz. Mosquitoes spend their larval lives wiggling around in pools of water, gobbling microorganisms and hiding out in the foliage. Tilapia seem to go after them using something of a tiered approach: larger fish nibble on aquatic plants, depriving larvae of hiding places; and the tilapia fry go right after the larvae themselves. Apparently, people postulated a century ago that hungry fish should be useful malaria-fighters, but no one had checked it out numerically.

It’s interesting that many Kenyans already farm tilapia (which are native to the Nile), leading one to wonder why existing tiliapia farms haven’t knocked down the malaria problem yet. (The town the researchers studied records 2,200 malaria cases per year; globally, more than 350 million people get malaria each year, and 1 million die.)

Chalk it up to business misfortunes: when a farming operation goes under, the abandoned fishponds collect water and breed hordes of mosquitoes. The prospect of restocking those ponds and at the same time clearing them of mosquitoes suggests a worthwhile place to invest development funds.

Image: a cool stamp collection

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smallfry.jpg

I’m sorry to report that yesterday’s post about disease-causing organisms in ocean water is only half the story: there’s also disease-causing chemicals out there, too.

Now I realize that in the back of pretty much everyone’s minds, there’s the knowledge that ocean water contains nasty chemicals. So I won’t take a lot of your time here – I’ll just remind you of a few names to keep track of.

Lead and mercury aside, most can be neatly tied up in one or a few generic terms: organochlorines, polyhalogenated aromatic hydrocarbons, polychlorinated biphenyls. Big names like DDT, dioxin, and PCBs fit into one or more of those categories. But as with microbes, it’s pretty difficult to keep the subcategories straight: what’s the difference between PCDD, PCDF, PBDE, PCN, or the murky-sounding DBP, or “chlorination disinfection byproducts”? HFINo***

But again, we can count ourselves lucky to have people who do know the difference – and who are getting pretty good at measuring it. A couple of recent studies did the math all the way through to estimating roughly how much of these chemicals a typical seafood-enjoyer ingests.

For instance, a typical Catalonian hombre might eat 1.53 nanograms of polychlorinated naphthalenes (PCN) in a day – more if he eats a lot of salmon or sole and less if he prefers shrimp or cuttlefish. A Belgian study analyzed “market baskets,” comparing the chemical contamination of many typical foods. Fish topped the list of most contaminated, with PBDE levels nearly twice as high as the second place (dairy and eggs). Fast food was a distant third, with steak and chicken breast registering even safer. The authors noted one exceptional salmon filet that raised the bar, coming in with a PBDE concentration five times the seafood average and nearly an order of magnitude above second place.

In eastern U.S. fish markets, you can find more than 20 times as much PCB and PBDE in wild bluefish as you can in farmed salmon (and wild salmon had only half as much of these chemicals as farmed salmon).

That may sound like yet another plug for wild salmon, but then again, consider the wildness of your salmon’s homeland. Does it cavort in essentially urban waters like Portland’s Columbia River or the Nisqually estuary south of Seattle? Because if it does, it’s likely to pick up PCBs, DDTs and PAHs from runoff.

Young chinook salmon heading out to sea from the Duwamish Estuary, the Columbia River and Yaquina Bay had PCB levels in NOAA fisheries’ red zone – above 2,400 nanograms per gram of fat. (I imagine it has been argued that as these salmon grow up in relatively pure open ocean waters, those levels will come back down. But still.)

It’s also curious that coho salmon sampled from the same locations as the chinooks were consistently less contaminated – by factors of 2-5. Sounds like a mystery for the ecologists to solve.

There’s still the question of how much and how steady of a diet of these compounds one needs before cancer sets in. Part of the trouble lies in toxicity differences among the many compounds (called congeners) that are contained within the categories I listed at the top of this increasingly glum post. Unfortunately, for almost every one of those thousands of congeners, we just don’t know specific toxicity levels.

Well, if it’s any comfort to you, all those omega-III fatty acids are still really good for you.

Image: Alaska’s Wildlife. Thanks to SeaWeb for the tips.

***HFINo = HellifIknow

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pencilchew.jpgMaybe the occasional Scribble Reader has wondered just who in the heck this Scribbler is. But let me tell you, that ain’t nothin’ compared to how much I wonder who the heck you guys are.

But that’s the beauty of Web 2.0, ain’t it? No more agonizing over the wording of your letter to the editor of Omni Magazine in the hopes of seeing your name in print. Just hit the Comments button and fire away.

So here’s your chance to do some scribbling of your own and fill me in on one or more of the following 15 pressing questions:

1. How did you get here? (no need to get cosmic on this one)

2. Have you visited this site before?

3. Are you just here for the baby turtles? (you would not believe how many people search the Internet each day for baby turtles)

4. What kind of posts do you like the best? (a) ocean science (b) climate change (c) birding (d) surfing (e) other?

5. Are the posts (a) about right or (b) too damn long?

6. Would you like more coverage of (a) climate change (b) islands being devastated by rats (c) weird deep-sea creatures (d) earthquake-type stuff (e) celebrity feuds and/or adoptions (f) sex (g) atmospheric physics (h) other (please specify)?

7. How educated are you: (a) made it out of high school; curious about the world (b) still interested in most things (B.S.) (c) able to detect the infantile flaws in some stories; peripherally interested in all the rest (M.S.) (c) basically humoring me (Ph.D.)?

8. Do you wish the words I use were (a) longer (b) shorter (c) funnier (d) snarkier (e) less stupid (f) rhyming?

9. Do you occasionally wonder what possesses me to spend an hour or so writing about such obscure topics?

10. More pictures? (Of what?)

11. Are you not leaving comments because (a) the posts arrive fully formed and inviolable (b) you never make it to the end of a post (c) it’s interesting, just not that interesting (d) try writing about something that matters (e) you have a lingering feeling that even though only a tiny fraction of the world’s population will ever look at a comments page, you might come off sounding stupid and someone, somewhere, might snicker at you from the lonely confines of their poorly lit hovel

12. If scientists were to turn their collective intellectual power toward designing one and only one robot animal, what animal should that be?

13. I am an heir/heiress and I would like to contribute ___ million dollars to further the Scribbler agenda

14. Do I know you? How?

15. Setting aside the surfing and the birding for a moment, if there was one thing in the world you’d like me to write about, what would it be?

I’m really not kidding about this. Answer as much or as little as you see fit. Post a comment – or – if you don’t feel like going totally public – send aphriza at gmail dot com an e-mail. Thanks for reading.

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hockeysticks.jpg

Amid all the gloomy projections about the effects of climate change, a study in today’s Science reports a new effect that might inject some hope into the sorry state of ocean fisheries: increased upwelling.

What’s upwelling? Funny you should ask. I was surfing in dreadfully cold Monterey Bay water last week when I turned and looked straight in the eye of a surfacing gray whale about 40 meters away. Both my ice-cream headache and the whale’s presence were products of upwelling, a fact of life along the western coast of North America and other continents.

During upwelling, vagaries of wind patterns and fluid dynamics draw very cold, nutrient-laden water up from the depths, freezing surfers’ skulls and kick-starting a food-chain party for krill, squid, fish, seals and whales. (For more specifics, see Bay Nature.) Upwelling zones around the world occupy less than 1 percent of the ocean, but account for 20 percent of the world’s fish catch.

In the new study, Helen McGregor from Germany’s University of Bremen and colleagues used sediment records to reconstruct the sea surface temperature at Cape Ghir, Morocco, over the last 2,500 years (around 2,490 years longer than previous studies of upwelling and climate change). The record showed colder waters – indicative of upwelling – during warm times like the Medieval Warm Period. But the strongest signal by far came during the twentieth century, when water temps dropped by 1.2 degrees C. If the standard air-temperature records look like a hockey stick, the water temperatures look like a mirror image.

But how could global warming do anything to change ocean currents? The authors suggest that more atmospheric CO2 could change the air-temperature balance between coastal land and waters. That would change the prevailing air pressure (i.e., weather systems), and the pressure difference would fuel stronger winds along the coast, stirring more upwelling. (See the Science article for a suitably technical description of this.)

With ocean fisheries in dire trouble (thanks to population growth and the fact that seafood is so yummy), increased upwelling could nourish more fish and slowly help us out of trouble in that respect. Upwelling also brings up centuries-old water that has never seen our CO2-rich atmosphere. That deep water would draw more CO2 out of the atmosphere than a similar amount of surface water. (Although this sounds good from a global-warming standpoint, it would speed the acidification of the oceans, a slowly building nightmare that Elizabeth Kolbert recently discussed for the New Yorker.)

One of the major problems with getting people to take notice of climate change is its complexity: we can’t predict exactly what’s going to happen, and we can’t even assemble a complete list of the kinds of things that will happen. Often, this uncertainty winds up skewed into either a simplistic doomsday scenario or a “jury is still out” assessment – both rather easily dismissable, I’m afraid. Fortunately, the scientists are still out there, assiduously working out the specifics.

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red knots

Two regrettable recent stories, each with mammals in the villain’s role: The humble mouse terrorizes seabird populations on a remote island; and Dutch shorebirds abandon a marine reserve because of shellfish dredging.

In far and away the more macabre story, on tiny Gough Island in the South Atlantic, thousands of endemic albatrosses and hundreds of thousands of petrels are being gnawed to death by house mice run out of control. Sorry if it sounds like TV news hyperbole – it isn’t.

After escaping onto the island from fishing boats a century ago, the mice have bulked up to twice their normal body size and surged to an estimated 700,000 strong on the island (that’s about half again as dense as people in San Francisco). Through constant, aimless nibbling, one imagines, they learned that the docile chicks around them were full of protein and fat.

The knee-high, 20-pound chicks, for their part, remain flummoxed, never in their evolutionary past having dealt with mammalian predators attacking from below. Scientists estimate the carnage at more than 700,000 chicks each year. New Scientist has the story, which hit the South African newspapers as well. (thanks Charles)

Some 6,500 miles to the north, in Holland’s Wadden Sea, even good intentions lead to bad news. Resource managers tried to allow shellfish dredging on the same mud flats where half of Europe’s red knots (see picture) feed for – you guessed it – shellfish.

The science of the study is ferociously good. The authors sampled shellfish availability in 2,800 different locations in each of five years. They traipsed across those same mud flats scraping up red-knot droppings to analyze what they’d been eating. They captured the birds and put bands on their legs to track their yearly survival – and while they were at it they even measured the birds’ gizzards with an ultrasound, for crying out loud. (Knots swallow mussels whole, then crunch up the shells in their gizzards to get to the flesh.)

Dredging didn’t reduce shellfish numbers appreciably, but it did hurt their quality as knot food – more shell and less flesh. Analysis showed that unless a knot could expand its gizzard capacity during the season, it likely could not eat enough food to meet its energy requirements. The result, the scientists calculated, was 58,000 knot deaths over five years, and the departure for parts unknown of four out of every five knots that used to frequent the Wadden Sea.

The good news is that the Dutch government halted dredging in 2004. But the bad news is not just bad for shorebirds. It’s bad news for conservation, because one of the encouraging selling points of marine protected areas is the idea that we can balance resource extraction (and jobs) with habitat protection. This study adds to the evidence that it’s simply harder than that.

(from PLoS Biology: news story and research article; image: Varnamo bird club)

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A swath of Namibian waters favored by fishing fleets seems to have been taken over by jellyfish – big ones, and lots of them. A new scientific survey found more than four times as much jellyfish (by mass) than fish in a 30,000 square mile stretch of once-prime fishing grounds. And 99% of the jellyfish sample was made up Aequorea forskalea, a once-rare whopper that can be a foot or more across and weigh as much as a wet chihuahua.

 

purple-striped jellyNow, I’m just as enthralled by jellies’ strange beauty as the next envious landlubber. But the sudden appearance of prizewinning jellies in Namibian waters seems to have come at the expense of fish stocks – perhaps even as a price of overfishing.

The Benguela current nourishes the Namibian waters with strong upwelling that brings nutrients to the surface and kick-starts binges of productivity by phytoplankton. That starts off a feeding frenzy among all the little copepods and other zooplankton, and the party continues all the way up the food chain until, in normal circumstances, you end up with shimmering schools of fat, happy mackerel, hake, and herring. (Kathleen Wong has a nice article on upwelling in the new Bay Nature.)

Overfishing subtracts, via nets wriggling with fish, a big, visible piece of this scenario. But it adds something too: scads of choice prey in the form of uneaten copepods, larvae and small fish. Enter the jellies. You can almost see them smiling and rubbing their tentacles together.

Research cruises in the 1950s rarely reported large jellies, as Christopher Lynam (Ph.D. student, University of St. Andrews, UK) and his coauthors note in this week’s Current Biology paper. Now, an estimated 12 million metric tons in the authors’ study area are clogging power plant intake pipes, covering fish catches with a layer of stinging slime, and even fouling diamond mining equipment.

The authors suggest a more worrying possibility, too. With scores of jellyfish eating fish food as well as fish larvae, the depleted stocks of market fish may not soon get the chance to rebuild their numbers. I suppose we can only wait and see. And start working on beer batter that makes jelly-guts taste good.

Photo disclaimer: Not being able to run over to Namibia to snap a picture of A. forskalea, I used a stand-in jelly. It’s a purple-striped jelly photographed in Monterey Bay National Marine Sanctuary. From the NOAA Photo Library.

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