“The bluefins’ habitat requirements are relatively exact so we can predict with reasonable accuracy where bluefin tuna are likely to be spawning at any given time based on oceanographic data continually being gathered by satellites and weather buoys,” said lead author Steven Teo of the University of California at Davis. “This is in stark contrast to yellowfin tuna, which exhibit much more generalized environmental preferences.” The fidelity to breeding areas over time detected in this study is reminiscent of salmon returning to their natal stream to spawn.

Bluefin tuna are among the most valuable fish in global markets. The International Commission for the Conservation of Atlantic Tunas (ICCAT, http://www.iccat.int) currently manages the Atlantic bluefin tuna as two distinct populations, with western Atlantic spawners of the Gulf of Mexico forming a distinct population genetically from the eastern spawners of the Mediterranean Sea. The western Atlantic stock has suffered a significant decline in spawning stock biomass since 1950, and a 20-year rebuilding plan has failed to revive the population or the North American fishery. The failure of the Gulf of Mexico spawning population to rebuild, as well as the scope of illegal and under-reported catches — particularly in the Mediterranean Sea — are of such major concern that the species was recently considered by the United Nations for endangered species listing in March of 2010.

Targeted bluefin fishing has been banned in the Gulf for over twenty years, but bluefin continue to be captured accidentally on pelagic longlines, often resulting in mortality. The study shows that bluefin tuna are captured in the Gulf of Mexico from January through June each year, and the highest pelagic longline catch rates are in April and May, during the bluefin spawning season.

The authors compared environmental preferences and spatio-temporal distributions of bluefin and yellowfin tuna as revealed by pelagic longline catch rates and scientific tagging cruise conducted by the Stanford University and Monterey Bay Aquarium team coupled with oceanographic data sets. Drawing on these data, a model was developed to determine the relative probability of catching bluefin and yellowfin tuna at a given place and time. This model showed that there are two major hotspot regions within the Gulf where bycatch occurs — one in the eastern Gulf of Mexico to the north of the Loop Current, and the other in the western Gulf of Mexico. Both regions are along the slope where the shallow continental shelf depth changes rapidly to the deep sea. It is within these hotspots that bluefin tuna prefer to spawn in circular, swirling water masses called “cyclonic eddies.” These eddies are more productive and slightly cooler than surrounding warm Gulf ocean currents. Yellowfin tuna, however, are much more widely dispersed throughout the Gulf of Mexico throughout the year.

These findings indicate that it would be possible to utilize spatial management techniques to protect western Atlantic bluefin tuna on their breeding grounds in the Gulf of Mexico without compromising the yellowfin tuna fishery, which could be carried out in other areas during the critical bluefin tuna breeding times.

Unfortunately, these findings also give cause for concern in light of the recent Deepwater Horizon oil spill. “Both catch data and electronic tags indicate the Gulf of Mexico along the continental shelf is the preferred habitat of this majestic fish. I think it is amazing how precisely we can predict where the bluefin are. Unfortunately their spawning habitat overlaps the Deepwater Horizon oil accident site, and the timing of the spill coincides with the time when we expect them to be there spawning” said senior author Dr. Barbara Block of Stanford University.

Funding for this study was provided by the Lenfest Ocean Program, the Tag-A-Giant Foundation, the David and Lucile Packard Foundation, the Monterey Bay Aquarium Foundation, the National Oceanographic and Atmospheric Administration and the Disney Foundation.Posted byCorinnaat11:52

NEW ORLEANS – The gooey oil washing into the maze of marshes along the Gulf Coast could prove impossible to remove, leaving a toxic stew lethal to fish and wildlife, government officials and independent scientists said.

Officials are considering some drastic and risky solutions: They could set the wetlands on fire or flood areas in hopes of floating out the oil.

They warn an aggressive cleanup could ruin the marshes and do more harm than good. The only viable option for many impacted areas is to do nothing and let nature break down the spill.

More than 50 miles of Louisiana’s delicate shoreline already have been soiled by the massive slick unleashed after the Deepwater Horizon rig burned and sank last month. Officials fear oil eventually could invade wetlands and beaches from Texas to Florida. Louisiana is expected to be hit hardest.

On Saturday, a major pelican rookery was awash in oil off Louisiana’s coast. Hundreds of birds nest on the island, and an Associated Press photographer saw some birds and their eggs stained with the ooze. Nests were perched in mangroves directly above patches of crude.

Plaquemines Parish workers put booms around the island, but puddles of oil were inside the barrier.

“Oil in the marshes is the worst-case scenario,” said Coast Guard Adm. Thad Allen, the head of the federal effort to contain and clean up the spill.

Also Saturday, BP told federal regulators it plans to continue using a contentious chemical dispersant, despite orders from the Environmental Protection Agency to look for less toxic alternatives. BP said in a letter to the EPA that Corexit 9500 “remains the best option for subsea application.”

The EPA didn’t immediately comment on BP’s decision.

Oil that has rolled into shoreline wetlands coats the stalks and leaves of plants such as roseau cane – the fabric that holds together an ecosystem that is essential to the region’s fishing industry and a much-needed buffer against Gulf hurricanes. Soon, oil will smother those plants and choke off their supply of air and nutrients.

In some eddies and protected inlets, the ochre-colored crude has pooled beneath the water’s surface, forming clumps several inches deep.

With the seafloor leak still gushing at least hundreds of thousands of gallons a day, the damage is only getting worse. Millions of gallons already have leaked so far.

Coast Guard officials said the spill’s impact now stretches across a 150-mile swath, from Dauphin Island, Ala. to Grand Isle, La.

Over time, experts say weather and natural microbes will break down most of the oil. However, the crude will surely poison plants and wildlife in the months – even years – it will take for the syrupy muck to dissipate.

Back in 1989, crews fighting the Exxon Valdez tanker spill – which unleashed almost 11 million gallons of oil into Alaska’s Prince William Sound – used pressure hoses and rakes to clean the shores. The Gulf Coast is just too fragile for that: those tactics could blast apart the peat-like soils that hold the marshes together.

Hundreds of miles of bayous and man-made canals crisscross the coast’s exterior, offering numerous entry points for the crude. Access is difficult and time-intensive, even in the best of circumstances.

“Just the compaction of humanity bringing equipment in, walking on them, will kill them,” said David White, a wetlands ecologist from Loyola University in New Orleans.

Marshes offer a vital line of defense against Gulf storms, blunting their fury before they hit populated areas. Louisiana and the federal government have spent hundreds of millions of dollars rebuilding barriers that were wiped out by hurricanes, notably Katrina in 2005.

They also act as nursery grounds for shrimp, crabs, oysters – the backbone of the region’s fishing industry. Hundreds of thousands of migratory birds nest in the wetlands’ inner reaches, a complex network of bayous, bays and man-made canals.

To keep oil from pushing deep into Louisiana’s marshes, Gov. Bobby Jindal and officials from several coastal parishes want permission to erect a $350 million network of sand berms linking the state’s barrier islands and headlands.

That plan is awaiting approval from the U.S. Army Corps of Engineers.

After surveying oil-stricken areas Saturday, Plaquemines Parish President Billy Nungesser said the berms were the marshes’ last hope.

“It’s getting in between all the cane and it’s working through from one bayou to the next,” he said.

Smaller spills have been occurring in the marshes for decades. In the past, cleanup crews would sometimes slice out oiled vegetation and take it to a landfill, said Andy Nyman with Louisiana State University.

But with the plants gone, water from the gulf would roll in and wash away the roots, turning wetlands to open water.

Adm. Allen said that where conditions are right, crews could set fire to oil-coated plants.

Nyman and other experts, though, warn it’s tricky. If the marsh is too wet, the oil won’t burn. Too dry, the roots burn and the marsh can be ruined.

BP PLC – which leased the sunken rig and is responsible for the cleanup – said Saturday that cleanup crews have started more direct cleanup methods along Pass a Loutre in Plaquemines Parish. Shallow water skimmers were attempting to remove the oil from the top of the marsh.

Streams of water could later be used in a bid to wash oil from between cane stalks.

In other cases, the company will rely on “bioremediation” – letting oil-eating microbes do the work.

“Nature has a way of helping the situation,” said BP spokesman John Curry.

But Nyman said the dispersants could slow the microbes from breaking down the oil.

White, the Loyola scientist, predicted at least short-term ruin for some of the wetlands he’s been studying for three decades. Under a worst-case scenario, he said the damage could exceed the 217 square miles of wetlands lost during the 2005 hurricane season.

“When I say that my stomach turns,” he said.Posted byJon Downesat18:59

As images of lifeless black-slicked birds and limp sea turtles begin to flood the media, it is becoming apparent just how catastrophic the Deepwater Horizon oil spill in the Gulf of Mexico is becoming. No one can predict how long it will continue and just how devastating this disaster might prove to be.

One thing is clear: The fragile ecosystems of the Gulf of Mexico are at great risk. Adding to the tragedy is that this is an incredibly vital area for countless numbers of species that come for refuge to this specific stretch of the country to breed, nest, spawn, feed, and rest during migration. Peak migration and breeding times are late-April through mid-May. It really could not be worse timing.

As noted in The New York Times, “even the frantic preparations to protect the most vulnerable coastlines likely will not prevent devastating harm to key species as the Gulf of Mexico oil spill hits shore at the worst possible time for migration and breeding.”

The U.S. Fish and Wildlife Service said the oil spill could affect up to 20 national wildlife refuges, and four covering more than 70,000 acres are in immediate concern.

Which animals are most threatened by this nightmare of an environmental disaster? Here is a round-up of some of those most in peril.

Brown Pelicans
The brown pelican has not had an easy time of it. The gracefully gangling birds were only removed from the endangered species list last year, and there is a major population, around 34,000 of them, currently nesting in the Gulf at the Breton National Wildlife

Diving birds are very susceptible to oil spills because they come into direct contact with the oil. A bird’s feathers overlap to trap air and provide the bird with warmth and buoyancy.

Birds that come in contact with an oil slick may get oil on their feathers and lose their ability to stay waterproof, they may ingest oil while trying to clean their feathers or when they try to eat contaminated food, and they may suffer long-term reproductive effects.

Brown pelicans were once the victims of hunters seeking feathers for millinery — which led to the birth of the National Wildlife Refuge System more than 100 years ago when President Theodore Roosevelt created the first refuge at Pelican Island in Florida.

In 1970, brown pelicans were officially declared an endangered species when their population was decimated by the use of DDT.

Sea Turtles
Of the seven remaining species of sea turtles known today, five of those species are in the Gulf. The oil spill area is one of the only foraging grounds for the most endangered species of the bunch, the Kemp’s ridley turtle, which is in its peak nesting season.

One of its two primary migration routes runs south of Mississippi. Loggerhead turtles, also endangered, feed in the warm waters in the Gulf between May and October.

The seven species that can be found today have been around for 120 million years (longer than the dinosaurs) — and many of these species live up to 80 years.

Dolphins
Several dolphin species routinely inhabit the northern Gulf, and already 12 bottlenose dolphins have been found dead due to the the oil spill, reports Yahoo! News.

When marine mammals come to the surface to breathe, they may inhale hydrocarbon vapors that can result in lung injuries; oil that comes in contact with the animals’ sensitive mucous membranes and eyes may produce irritations.

Young cetaceans may be injured due to ingestion of oil from contaminated teats when nursing; and there may be long-term chronic effects as a result of migration through oil-contaminated waters.

Shellfish And Crabs
According to The New York Times, the delta estuary is also the breeding ground for a lot of shellfish and crabs, says LuAnn White, director of Tulane University’s Center for Applied Environmental Public Health. “All of those are at risk for being damaged,” she said. “That estuary area is responsible for the breeding for about 40 percent of the aquatic life that’s in the Gulf,