Sea Lion Surge Prompts High Tech Tracking, Hazing & Killings
Producer: Vince Patton Videographers: Nick Fisher, Todd Sonflieth, Michael Bendixen Editor: Greg Davis Associate Producer: Cassandra Profita Additional Photos & Video: Columbia River Inter-Tribal Fish Commission, Cassandra Profita
On the last day of the spring salmon season on the Columbia River, sport anglers spotted competition for the fish they want to catch.Half a dozen sea lions poked up their heads just beyond the reach of fishing lines.Fisherman David Hylton from Redmond said, “I think we need to get them out of this system because this is not their natural habitat. They don’t live here.”Historically, sea lions did not come up the Columbia. Lewis & Clark spotted harbor seals. Archaeologists confirm finding remains of seals but not sea lions as high up the river as Celilo Falls.However, a growing number of sea lions have made the Columbia a frequent stopping point since the 1980s.
A record number of sea lions estimated at more than 2500 smothered the docks in Astoria in the spring of 2015. Nick Fisher/Oregon Public Broadcasting
In 2015, sea lions set records. More than 2500 covered the docks in Astoria and surveys estimated nearly 5,000 in the lower Columbia River.West coast populations have risen from about 180,000 in the late 1990s to nearly 300,000 in 2015.Biologists, anglers and tribes all believe the sea lions are killing too many endangered salmon.Government observers spend months watching the sea lions.The official estimates predict sea lions eat from 3,00 to 5,000 salmon, though in 2015 that jumped to more than 8,000.Doug Hatch, biologist with the Columbia River Inter-Tribal Fish Commission concedes they really don’t know how many salmon are eaten by sea lions.“We know there’s a lot of sea lions in the river,” says Hatch, “but we don’t know what their predation rate is on salmon.”Tribal biologists are experimenting with a high tech means to find out.They have captured a handful of sea lions, glued a tracking device to their head and released them back to the river.
Biologists glued an accelerometer tag to the head of a sea lion in an attempt to track its body motions. Columbia River Inter-Tribal Fish Commission
Hatch compares the tag to a fitness tracker people wear on their wrists. The sea lion tags measure the unique motions of a sea lion’s head, particularly when they eat.Sea lions often thrash about, throwing their food.It’s not play. They’re breaking the salmon up into pieces easier for them to eat.
A sea lion thrashes its head, tossing the salmon it has caught to break it up smaller to eat. Nick Fisher/Oregon Public Broadcasting
“When they do that it’s a very unique, distinctive movement of shaking,” says Hatch. “We think we’ll be able to capture that on the accelerometer tag.”Perhaps those tracking tags will show how many fish each sea lion eats when observers are not around to watch.Learning how many salmon sea lions eat is more than an academic question. It directly affects how many more sea lions may be put to death in future years.“It’s been quite controversial,” says Robin Brown, the marine mammal program leader for the Oregon Department of Fish & Wildlife.Brown says if the Army Corps of Engineers said it planned to modify Bonneville Dam in a way that would kill an additional 5,000 salmon each year, “It would never be permitted. The same is true from our perspective for the California sea lion predation on threatened and endangered salmon.”Biologists received federal permission to take more extreme measures.CRITFC helps with the first stage. They haze the animals by firing non-lethal noise-making shells from shotguns at sea lions near Bonneville Dam. The hazing lasts several months a year.
A Columbia River Inter-Tribal Fish Commission worker hazes sea lions with noise makers from a shotgun. Nick Fisher/Oregon Public Broadcasting
ODFW has regularly branded thousands of sea lions for the last several decades. The brands are large enough to be read by observers.If an individual sea lion has been exposed to non-lethal hazing and has been identified repeatedly eating salmon near the dam, that sea lion can be killed.That infuriates Ninette Jones, an activist with the Sea Lion Defense Brigade.Day after day, she arrives before dawn to watch and shoot video of the government’s sea lion trapping operation from the opposite side of the river.
Government biologists take select sea lions from traps to be euthanized at Bonneville Dam. Todd Sonflieth/Oregon Public Broadcasting.
Jones believes sea lions are scapegoats when the impact of dams kills far more fish.“We still had a million Chinook cross this dam. With our sea lions, with all the people, I think that’s pretty amazing,” says Jones. “For land mammals (humans) to allocate all the aquatic animals food source for themselves, I find that rather greedy.”In eight years, the government has killed 85 sea lions and transferred another 15 to zoos.Hatch, the CRITFC biologist, says he hopes their tracking tags will improve data showing whether sea lions are responsible for a substantial impact on salmon runs.“It’s circumstantial,” says Hatch. “You have a large population of sea lions and you have this loss of fish. But we need a predation rate. We need a way to link those together before we could say, without a doubt that it’s a sea lion problem.”Recent salmon runs in the millions have set records.But tribal and government biologists believe allowing several thousand fish each year to disappear to predators still poses too great a risk to the salmon.“None of us like the idea of having to kill animals, remove predators,” says Brown.ODFW says it has no plans to remove large numbers of sea lions; it will target only those individuals identified as repeatedly eating salmon near the dam.
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THE ANCHOVY “COLLAPSE”: ANOTHER MANUFACTURED CRISIS
Recent sensational media accounts trumpet the collapse of the central anchovy population. Environmental extremists are now calling for emergency closure of the anchovy fishery that takes place primarily in Monterey Bay. This hysteria is based on a study, funded by these same environmentalists, that claims the population has collapsed in southern California, has declined by 99 percent and now is at extremely low levels, with virtually all the fish concentrated nearshore in Monterey Bay. The scientific paper detailing study findings – still in peer review – is now being criticized for failing to consider the last 5 years of data, which document a big increase in recruitment for anchovy and sardine both in southern California and coast-wide. But that doesn’t stop the extremists from accusing fishermen of, in essence, taking “the last fish.” We are responding to the outcry in the media with facts and images to illustrate the fallacy of extremist claims of anchovy “collapse.” Fishermen are the vanguard of ocean observations. Here’s their side of the story:Corbin Hanson fishes for coastal pelagic species (CPS), mainly in southern CA: “I saw a large volume of anchovy show up on the southern CA coast beginning around 2011. I’ve seen lots of pinhead [small] anchovy in the Santa Barbara channel, and in 2014 Catalina Island was loaded with small anchovy. The largest volume of anchovy I’ve ever seen was running up coast from Point Conception to Monterey this summer – miles of anchovies from 30 fathoms depth to the beach. We couldn’t escape them; it was hard to see the bottom on the fathometer at times. We drove through hundreds of thousands of tons in one night this summer. Other fishermen saw the same thing I did – whales, birds, seals all gorging on anchovy.”Richie Ashley also fishes for both live bait anchovy and other CPS in S.CA“There has been major tonnage of anchovy in the Los Angeles / Long Beach harbor for more than a year. Almost all of it has been very small “pinhead” size. Another volume of slightly larger anchovy were in front of Newport Beach for several months. In June, Catalina was loaded with small pinhead anchovies – many thousands of tons. At the same time, we saw anchovy in the Santa Barbara channel in daytime as well, a lot of it! Whoever said there are no anchovies in southern CA has no clue!”Tom Noto has fished for 30 years, and fishes for anchovy in Monterey.“Fishermen catch anchovy on the edge of Monterey Canyon. These fish like to dive deep. We see schools of anchovy that color our fathometers red from bottom to near top. Our sonars mark schools that are hundreds of feet thick, but our nets just skim the surface of these schools. Fishermen up and down the coast are seeing the same thing: anchovies are everywhere, but we only fish them in Monterey Bay.The study is wrong and I feel our fishery is being assassinated without cause.”Neil Guglielmo has been fishing for 57 years up and down the West Coast, and is one of about eight fishermen who fish anchovy in Monterey.“ I’m on the water nearly every day and I’ve seen a big surge in the anchovy population in recent years. Anchovies now stretch from the “pinheads” fishermen see in Southern California all the way up the coast past Half Moon Bay, where a large group of whales was recently spotted feeding on anchovies. Our fishery simply skims the surface of anchovy schools that often run hundreds of feet deep. The allowed anchovy harvest is limited at 25,000 tons, leaving 75 percent of the biomass in the ocean as forage. Bottom line: there are plenty of anchovies in the sea. “
To illustrate, Neil photographed his sonar during one night fishing anchovy in Monterey:
The sonar shows a school of anchovy in front of the boat – one school representing hundreds of tons of fish. Schools this dense are plentiful in Monterey Bay and along the coast from Pt. Conception to Monterey and beyond. 
The fathometer on Neil Guglielmo’s fishing vessel Trionfo marked dense schools of anchovy on the bottom of the ocean across the entire mouth of San Francisco Bay, under the Golden Gate Bridge -- thousands and thousands of tons of anchovy. 
The Trionfo fishes for anchovy in Monterey Bay at night when the fish are near the surface. The boat is surrounded by birds, sea lions and other marine life, all eager to help themselves to the catch.
Climate change a likely culprit for declines in ocean fish
Fish populations off California’s coast have plummeted more than 70 percent in the last four decades, and scientists’ best guess is that climate change is to blame.
The precipitous decline has occurred ecosystemwide in the California current, a stretch of the Pacific that runs from the Pacific Northwest to Baja California, according to a recently published study. The decline can’t be pegged on a lone cause, such as overfishing or chemical pollutants.
There is one correlation: ever increasing ocean temperatures.
“The decline has been going on for four decades, and it hasn’t ever reversed, so it seems to us that it might be related to global climate warming,” said Tony Koslow, the lead author on the study and a researcher at Scripps Institution of Oceanography in La Jolla.
Natural variability might see fish populations fluctuate over a decade. But the decline this time around has been steady for half a century, leaving few options other than climate change.
Even as scientists examine evidence of decadeslong trends of declining fish populations, short-term threats have wracked marine ecosystems off California’s coast.
Last week, California officials warned people against eating Dungeness crabs because of a natural acid toxin that has contaminated them. An algae that produces the acid has grown exponentially because of warm ocean temperatures. The algae has made its way up the food chain and into the crabs.
Populations of certain commercially fished species also have suffered in recent years. The sardine fishery, for instance, was closed this year because estimated fish levels were below a certain threshold.
And for the past two years, increasing numbers of emaciated sea lions have been stranded on California’s shores. With warmer water, certain fish populations are lower and sea lions are seeing their food sources dwindle. Instead of sardines and anchovies, whose numbers are down, the sea lions are eating low-quality squid and rock fish.
“The food quality that’s available to the mothers, and they come back and then feed their pups, is now lower-quality food,” said Sam McClatchie, a National Oceanic and Atmospheric Administration scientist.
These changes largely have been attributed to a patch of warm ocean water lingering off California, called “the blob.”
But the new study, published last month in the journal Marine Ecology Progress Series, addressed trends that take decades to unfold, not months. And it revealed a decline that has more do with global climate change than any one particularly warm patch of ocean water.
The study combined two sets of data that hadn’t been analyzed before.
One was taken from cooling water intakes at coastal power plants that also suck in and kill some fish.
The other data came from one of the most extensive collections of fish larvae and ocean conditions in the country, compiled by the state’s California Cooperative Oceanic Fisheries Investigations program. For more than 60 years, scientists have measured ocean conditions off the Central and Southern California coast.
Four times a year, boats travel 500 kilometers offshore, taking measurements of temperature, nitrate levels, dissolved oxygen and other variables, from just below the surface to 210 meters deep.
The boats also collect water samples. Those are sent to the lab, where researchers count fish larvae under a microscope and sort them by species.
Counting fish larvae is a good stand-in for counting adult fish populations: if there are lots of larvae, scientists are confident there were a lot of adult fish reproducing to create those larvae. And sampling larvae in the top 200 meters captures most larvae-producing species, since that’s where they reproduce.
That fish numbers are declining isn’t surprising. What the new study shows is how evenly numbers are dropping for fish species across the spectrum, for the whole marine ecosystem, and not only for a handful of commercially fished species.
In the recent study, larvae populations in the open ocean had declined 72 percent since 1970, while fish levels at power plant intakes dropped 78 percent.
Such consistent declines call into question many of the usual suspects for fish decline, such as overfishing, chemical pollutants and power plant water intakes, according to the researchers.
“We’re seeing this consistent pattern across species,” said Eric Miller, an author on the paper and scientist at MBC Applied Environmental Sciences, an environmental consulting firm. “It’s beyond fishing, it’s beyond pollution, it’s beyond power plant ocean intakes. It’s something in the environment itself.
“You can’t look locally to try to understand all the problems and concerns we have in the ocean. It’s something that’s going on in a much bigger, regional scale,” he added.
Only ocean temperatures correlated with fish declines. The scientists found that cold-water fish are declining the fastest, Miller said. And while warm-water fish are replacing them, they’re doing so at a slower rate than the cold water fish are disappearing.
While chemical pollution isn’t benign, it couldn’t have done such widespread damage to the ecosystem, Miller added.
Chemicals like DDT have killed many marine and other creatures. For instance, the pesticide became famous and then was subsequently banned in the U.S. because it thinned bald eagles’ egg shells, causing that bird’s population to crash in the 1960s. But the current declines in fish population can’t be explained by one chemical – nor by the power plant water intakes, which would have a very local effect on the fish population.
Population declines have been observed far from the coast, where chemicals enter the water and fish get sucked into cooling systems.
“You can’t look at any single thing and say, ‘That’s the problem.’ There’s something much more pervasive,” he said.
While heavy fishing directly reduces numbers of certain fish species in the open ocean such as sardines and anchovies it probably isn’t causing the ecosystemwide declines.
Fish that live at middle depths have suffered – and they don’t wind up in fishermen’s nets either on purpose or accidentally.
Relying on fish counts from commercial fishermen’s nets can mask population declines for fish that form large schools, according to another study Miller published several years ago.
Such fishery data calculates population based on a formula that compares the number of fish caught to how much effort is expended catching those fish.
Even as fish populations decline, fishermen are skilled enough to find them easily and still catch large numbers of them. The large catches suggest the population is robust, even as fish numbers dwindle.
For that reason, Miller and his colleagues relied on fishery-independent data in the new study.
They included open-ocean data collected by the state’s California Cooperative Oceanic Fisheries Investigations program, which was created in the early 1950s to figure out why the sardine stocks collapsed.
The collapse of the sardine fishery, a major business in the 1930s, was documented in John Steinbeck’s 1945 novel “Cannery Row.”
Today, the oceanic data collection program is considered the gold standard for data collection and has been used for about 600 scientific studies examining fisheries.
It was instrumental in uncovering how El Niño increases the heat content of the ocean, lowers nutrient production and wrecks certain fisheries, such as squid.
Those decades of data reveal the Pacific Ocean isn’t the same place it was half a century ago, said John McGowan, a study author and researcher at Scripps.
“The California current is changing,” he said.
Read the original post: http://www.ocregister.com/
Hilborn Says Newsweek Article “May Set a New Record for Factual Errors”
— Posted with permission of SEAFOODNEWS.COM. Please do not republish without their permission. —
Copyright © 2015 Seafoodnews.com
November 3, 2015Dr. Ray Hilborn, Professor in the School of Aquatic and Fishery Sciences at the University of Washington, takes issue with Newsweek’s August 9, 2015 article “Our Taste for ‘Aquatic Bushmeat’ Is Killing the Sea” and its bleak picture of the state of worldwide seafood.The article quotes Dr. Sylvia Earle, a former chief scientist at NOAA and now a National Geographic explorer-in-residence.The article incorrectly claimed that 90 percent of global stocks had been removed in the last half-century and that 90 percent of the worlds stocks were unsustainably harvested. The latter statement was corrected to 29 percent after CFOOD staff pointed out the error.CFOOD is a coalition of fisheries scientists from around the world who are correcting inaccuracies about stock abundance, management measures, and global ocean status. They back up their corrections with scientific data. Their website cfooduw.org lists myths “that won’t go away” and corrects them. For example, there are summaries of global stock assessments that show that stocks will not collapse by 2048, 70 percent of the world’s fish are not overfished, and we are not fishing down the food chain, among others.Newsweek writer Douglas Main referred to a 2003 report that estimated large fish populations (three species of tuna) had crashed worldwide based primarily on catch per unit of effort, now considered a biased metric to gauge abundance.The 2003 report was repeatedly refuted in subsequent scientific papers. By 2011, a correct estimate of 28.8 percent of fish stocks were considered fished at a biologically unsustainable level.“The graph below shows the trend in the number of stocks overfished according to the Food and Agriculture Organization of the United Nations,” wrote Hilborn. It shows that after rising steeply between 1970 and 1990, the rate of increase in overfishing rapidly declined, and total overfishing is now stands at 28.8% of global stocks.
Hilborn pointed out that Newsweek’s article repeated the often rebutted statement that 90 percent of the large fish of the ocean were gone by 1980.“Yet again the author and Dr. Earle don’t seem to have read the scientific literature or have conducted any due diligence with respect to the facts in the article. Certainly those stocks declined from 1950 to 2005 but they were mostly not overfished and the declines were a natural part of newly developing fisheries," says Hilborn.“In fact, in many places of the world overfishing is disappearing and stocks are increasing. Cod in most of the North Atlantic are coming back, and Atlantic bluefin tuna is increasing rapidly.“The idea that on the whole global fisheries are not sustainably managed is out and out wrong,” Hillborn wrote. “In many places such as North America, Australia, New Zealand, Iceland, and Norway fisheries are sustainably managed.”Overfishing that has occurred is now declining in many countries including the European Union members, Chile, Peru, South African, Japan and Argentina.“Certainly there are many fisheries in the world that need better management, but we must understand where and why some stocks are overfished and this requires good science,” Hilborn said.Earle admonished people who don’t think about what kind of fish they eat or where it is from. “This kind of traceability is hard to achieve,” Hilborn points out, especially in areas where regulations are lax and fishing is strong, such as parts of Asia and Africa.“Dr. Earle is an advocate for minimizing human impacts on the ocean but and has frequently argued that we should not fish at all. This is despite the fact that fish provide essential nutrition and employment for many of the world’s poorest people.“The challenge is to assure that all of the worlds fisheries are sustainable and totally incorrect statements are no help in achieving this goal,” Hilborn said.
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California’s Dungeness crab season start in doubt due to toxic algae offshore
With less than a week to go before sport anglers can begin setting traps for Dungeness crab, a persistent bloom of toxic red algae off the Pacific Coast is threatening to disrupt the start of the catch and one of California’s most valuable fisheries.State officials are awaiting test results they hope will come back by midweek before deciding if they will delay the Nov. 7 recreational start, as well as commercial seasons set to begin a week later, Fish and Wildlife personnel said.Concern about a powerful neurotoxin called domoic acid produced by certain marine algae is driving the deliberations in California and in other regions, including Washington state, where much of the Dungeness crab fishery was closed through the summer because of high levels of domoic acid found in crustaceans there.In California, absent current test results to evaluate, “everything kind of is up in the air right now,” state Fish and Wildlife Department spokeswoman Jordan Traverso said Friday.Overall, algae blooms that peaked in late summer off the California coast are reported to be diminishing, according to Pete Kalvass, senior environmental scientist with state Fish and Wildlife.But domoic acid levels of even 21 parts per million in crab meat are considered potentially dangerous, Traverso said.“We don’t know what the next step is until we get results,” said Christy Juhasz, an environmental scientist with the agency.Barring a delay, the recreational crabbing season will start Saturday, Nov. 7, and can be expected to draw thousands of eager fishermen to the North Coast for what’s become an increasingly popular undertaking, spawning traditions that bring family and friends together, filling campgrounds, boat ramps and bays.Campsites for the crab opener generally are booked months in advance in anticipation of the first-day scrum.“We’re busy in the summer, and it used to be just the summer that we had the most interest,” said Willy Vogler, co-owner of Lawson’s Landing on Tomales Bay. “Then, in the last decade or so, November has become like another summer, and it’s primarily due to the Dungeness crab season opening up. … Losing the crab would be bad.”
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Crab fishermen volunteer to protect tangled whales
It’s an increasingly common site along the West Coast: a 50-foot-long whale breaking the surface of the water, hundreds of feet of fishing gear wrapped around its torso and fins, cutting into its skin and trailing behind it. If the whale is lucky, a whale entanglement team will find it in time and successfully free it from the heavy equipment. If the whale is unlucky, it may succumb to infection, become too tired to feed, or drown.A seemingly unlikely ally has emerged in the fight to protect the whales of the West: the fishermen themselves. On Tuesday, Oct. 20, The Nature Conservancy and National Oceanic and Atmospheric Administration held meetings in three locations along the California coast to train fishermen to be first-responders for whale entanglement. Almost 100 crab fishermen attended the voluntary trainings – nearly a third of California’s crab fleet.More West Coast whales were caught in fishing gear in 2014 than any other year, according to reports by NOAA. 2015 is on course to break that record, and the Dungeness crab season has yet to begin.No one knows why reports of entanglements have increased so rapidly.“I don’t know anyone who has ever seen a whale caught up in gear, even the old-timers,” said Capt. Geoff Bettencourt, a fourth-generation commercial crab fishermen based in Half Moon Bay who attended the training. “But now it’s all over the news. It seems rampant.”One reason might be the dramatic increase in humpback whale populations, suggested Tom Dempsey, senior Fisheries Project Director at The Nature Conservancy. Another could be changes in whale behavior. Whales seem to be staying in California longer and spending more time close to shore, where most crabbing takes place. But this may not be the full picture.According to Dempsey, there’s not a lot of data to work with. It’s unclear what types of gear are most likely to harm whales, and the areas with the most reports might not represent where the whales are being entangled.Dempsey hopes the fishermen can help shed some light on the mystery. “Nearly 100 fishermen participated in our training. Collectively, they log thousands of sea days annually.”Not only will crab fishermen help researchers understand where and how the whales are being injured, they can help whale entanglement teams locate and rescue whales, acting as front-line triage. At the training, fishermen were taught to document and evaluate the condition of entangled whales, and taught to correctly report their locations to rescue teams.If the pilot program is a success, Dempsey hopes to hold more trainings. Eventually, fishermen may be taught to tag entangled whales with satellite and telemetry transmitters. This would help entanglement networks locate and rescue whales more easily.Dempsey said the response from fishermen has been overwhelming. “Usually on sensitive issues like this, everyone retreats to their different sides and there isn’t a lot of collaboration. This has been the opposite. The industry has stepped forward and really wants to be a part of the solution.”Bettencourt wasn’t surprised by the fishing industry’s response. “People think that all a fisherman cares about is catching fish, and that’s the farthest thing from the truth. If we mess up the ocean, our families suffer. We lose our livelihood. We lose everything. We want to see it healthy more than anyone.”
Read the original post: http://www.thecalifornian.com/story/news/my-planet/2015/10/23/crab-fishermen-volunteer-protect-tangled-whales/74489382/
Pollution Could Buy an Extra Decade of Arctic Sea Ice
Air pollution could help preserve ice but that still doesn’t make it good
Credit: NASA
Arctic sea ice continues to dwindle at an exceptional pace. Summer sea ice has declined at a rate of 13 percent per decade, and the rate has sped up in the last 10 years.The main driver for Arctic sea ice’s disappearing act is the rising ocean and air temperatures driven by human greenhouse gas emissions. But that isn’t the only factor affecting Arctic sea ice. Air pollution also plays a role and can actually slow down warming.In the tug of war, aerosols don’t necessarily counter the impacts of climate change on sea ice (or the planet as a whole for that matter). But new research shows that air pollution could buy the planet a decade of ice in the Arctic.“It shows it’s a complex picture,” Nathan Gillett, a research scientist at Environment Canada, said. “Aerosols have quite a substantial impact on Arctic climate.”Gillett co-authored the new research in pre-publication with Geophysical Research Letters. The findings show that aerosols have blunted 60 percent of the warming in the Arctic through the 20th century, a notable statistic given that the Arctic has still warmed at twice the rate as the rest of the planet.This summer saw the fourth-lowest extent on record (and this winter also saw the lowest winter maximum on record). With temperatures projected to keep rising, it’s only a matter of time before the Arctic experiences an ice-free summer.Going forward, aerosols—small particles that make up air pollution and reflect sunlight back into space—could continue to keep the northern reaches of the planet somewhat cool. Using a middle of the road carbon emissions scenario (which is a little optimistic given currently pledges) as well as rising aerosols, Gillett and his team show that the Arctic is likely to see an ice-free summer around 2057.When his team ran the same scenario but capped air pollution at 2000 levels, ice-free summers in the Arctic started more than a decade earlier in 2045.
Read the original post: www.scientificamerican.com
Ocean Heat Maps Reveal Secrets of Migratory Fish Like Tuna
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Copyright © 2015 Seafoodnews.com
SEAFOODNEWS.COM [United Press International] By Brooks Hays - October 22, 2015By comparing the movements of tagged fish with ocean heat content maps, researchers at the University of Miami were able to uncover unique patterns in migratory fish behavior.Their analysis proves that large migratory fishes, like yellowfin and bluefin tunas, blue and white marlin, and sailfish, are drawn to ocean fronts and eddies.Two analytical breakthroughs made the revelation possible. First, researchers realized satellite mapping of ocean heat content, or OHC, a measurement of heat stored in the ocean's upper layers commonly used for hurricane forecasting, could also be used to pinpoint the position of fronts and eddies.Second, researchers were able to improve the algorithm that analyzes satellite tags from migratory fish. Together, these advances allowed researchers to compare OHC mapping and fish movements."Using an advanced optimization algorithm and OHC maps, we developed a method to greatly improve geolocation accuracy and refine fish movement tracks derived from satellite tags," lead researcher Jiangang Luo, a scientist at Miami's Tarpon and Bonefish Research Center, said in a press release.The data showed that large migratory fish prefer to follow the boundary lines of large water features."Using the OHC approach in a new way offers an unprecedented view of how these animals move with currents and eddies in the ocean," Nick Shay, a professor of ocean sciences at Miami's Rosenstiel School of Marine and Atmospheric Science, said in a press release. "Our study provides a more detailed picture of the ocean ecosystem as an entity."Eddies are circling masses of water that spin off of current fronts. The swirling water pulls nutrients to the surface, making them an ideal place for hungry fish to hang out. Fronts are currents that follow the boundary line between two large water masses, distinguished by a difference in temperatures or salinity.In the Gulf of Mexico, warm water eddies regularly spin off of fronts formed by masses of Mississippi River water. In the summer and fall, these eddies can energize and intensify a hurricane or tropical storm."Our new method shows that hurricanes and highly migratory fish share at least one common oceanographic interest -- warm swirling ocean eddies," said Jerald S. Ault, a professor of marine biology and ecology at Rosenstiel.The new research was detailed in a paper published this week in the journal PLOS ONE.
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