Tuesdays with Turtles – Green Turtles Deluged?

Byoliveridley

I mentioned recently that elevated temperatures from climate could skew sea turtle sex ratios towards females. The featured news article highlights research which speculates that storm surges caused by increased hurricane (they call them cyclones in Austraila and India) intensity from climate change might lead to the flooding of green turtle nests in Florida, hastening their extinction. Why only the greens? Because they nest later than the other turtles and tend to be around during the height of the Atlantic hurricane season.

We know from previous research that loggerhead turtles have been nesting earlier because of elevated temperatures. Will the greens catch up. More pertinently, will there be enough survival of the early nesters of this generation to keep a viable population going while the whole population adapts? As with all climate change suspense thrillers, only time will tell… Depressing, at any rate.

News in Science – Cyclones may blast turtles to extinction – 15/05/2007

More severe tropical cyclones expected as a result of climate change may lead to the extinction of the green sea turtle in some areas within 100 years, researchers say.

The cyclones are expected to threaten how well the turtles nest and hatch eggs, placing pressure on already endangered populations, some of which are also threatened by fish trawling.

Researchers including PhD candidate David Pike, from the School of Biological Sciences at the University of Sydney, report their findings online in the journal Oecologia.

The researchers studied more than 40,000 sea turtles nests on an uninhabited, 38 kilometre stretch of beach along the Atlantic coast of Florida from 1995 to the end of 2005.

Each night during this period researchers surveyed the beach for turtles emerging to lay eggs, or for tracks of turtles that had already deposited eggs.

The stretch of beach is home to the loggerhead, green, and leatherback sea turtles, which start nesting at the beginning in April and end in late September.

This nesting season largely coincides with region’s tropical storm season, which runs from June to November.

Leatherback turtles (Dermochelys coriacea) and, to a lesser degree, loggerhead turtles (Caretta caretta) get around this by nesting and hatching earlier.

Only nests laid late in the season are inundated with seawater during storm surges.

But green turtles (Chelonia mydas) nest last.

Their entire nesting season occurs during Florida’s tropical cyclone season, which means their nests and developing eggs are extremely vulnerable to being washed away and killed.

Researchers are concerned that increases in the severity of tropical cyclones in the future may cause green turtle nesting success to worsen.

Similar Posts

  • |

    Killer nets reinstated

    Byoliveridley

    Council Decisions: March 2006

    Drift Gillnet Management

    The Council adopted a recommendation to NMFS to authorize an exempted fishing permit (EFP) that would allow drift gillnet fishing in the current August 15-November 15 closed area. The EFP fishery would be governed by several requirements for all vessels, including, to carry an observer; to limit total fishing effort in the EFP fishery to 300 sets; to immediately cease the EFP fishery if, and when, two leatherback sea turtles were encountered by the fishing gear; and to immediately cease the EFP fishery if one mortality or serious injury occurred to any of the following marine mammals: short-finned pilot whale, sperm whale, fin whale, gray whale, humpback whale, or minke whale.

    And, with that, starts the rather egregious practice of drift gillnet fishing. The restrictions seem fairly tight, an observer on every boat, and end to the fishery after two incidences of capture. There is definitely more than meets the eye here, I don’t know what. Drift gillnet fishing is well documented to cause turtle catch, this from the 1998 Fishery Bulletin for 1990-1995

    In the drift gillnet fishery, seven out of 387 mammals observed entangled were released alive. In the set gillnet fishery, five out of 1,263 mammals observed entangled were released alive. Estimates of incidental kill are presented along with estimates of entanglement for species that were observed to be released alive. For the period under consideration, the estimated mortality for the drift gillnet fishery was over 450 marine mammals each year. A total of 20 turtles and 3 seabirds were observed entangled during the entire period. The most frequently entangled species in this fishery were common dolphins, Delphinus spp., and northern elephant seals, Mirounga angustirostris. Estimated cetacean mortality in the driftnet fishery decreased from 650 in 1991 to 417 in 1995; pinniped mortality decreased from 173 in 1991 to 116 in 1995. Estimated cetacean mortality in the set gillnet fishery ranged from a high of 38 in 1991 to a low 14 in 1993; pinniped mortality rose to a high of 4,777 in 1992 and then decreased to 1,016 in 1995. We postulate that there has been a decline in the number of pinnipeds and cetaceans in the setnet fishery owing to area closure. No similar proposal can be made for the driftnet fishery. The most frequently entangled mammals in the setnet fishery were California sea lions, Zalophus californianus, and harbor seals, Phoca vitulina. Six turtles and 1,018 seabirds were estimated entangled in this fishery during the NMFS Observer Program from July 1990 to December 1995.

    So what’s the deal, this thing caught 20 turtles in 5 years, so it is going to catch turtles, no doubt about it. Anyone who does not get what the death of one adult sea turtle means read this. Sea turtles are wonderfully fragile animals given their size, they take long to mature sexually, they do not breed all that much and less than 1% of turtle hatchlings survive to adulthood. Leatherbacks are highly endangered.

    I have a feeling that this is the first part of a one-two punch intended to reinstate the famed turtle killer long line swordfish nets on the pacific coast. The “proof” that these nets do not catch turtles will be used to lobby for longline swordfishing in, oh say three months?

  • Bonus Turtle Coverage – The Great Turtle Race

    Byoliveridley

    Great Turtle Race

    Follow eleven turtles as they sprint from Costa Rica to near the Galapagos. Each of them has a corporate sponsor, and at 20 miles an hour, they will get there in a couple of weeks! I think Billie’s going to win, but the leatherback turtle is in bad shape, endangered due to poaching, adult mortality and habitat loss. They may be gone very soon.

    Here’s the flickr page for the race, some beautiful pictures already.

  • Tuesdays with Turtles – Poaching in Mexico

    Byoliveridley

    This article brings up some interesting information about sea turtle poaching in Mexico, including the fact that sea turtle eggs are considered aphrodisiacal in certain cultures…

    Real Men Don’t Eat Turtle Eggs : To Fight Turtle Poaching, Campaigners Hit Below the Belt (By C.J. Bahnsen)

    But there have been recent gains. WiLDCOAST, a small conservation organization also co-founded by Nichols, has implemented a media campaign. It started in 2005, when Argentine singer and Playboy model Dorismar attracted controversial attention by appearing in television and poster PSAs, hitting Mexican men—who eat turtle eggs mistakenly believing they are aphrodisiacs—below the belt. The message above a salacious Dorismar reads: “My man doesn’t need to eat turtle eggs; because he knows they don’t make him more potent.” The bold campaign reached a global audience of 300 million and resulted in a decrease in consumption of sea turtle eggs.

    Well, the unfortunate thing about aphrodisiacs is that if you believe, it works! So, I guess a Playboy model telling you that sea turtles eggs are baloney may work. They author does say there was a decrease in consumption, but presumably, it is not quite that easy to ascribe causation relationships to particular parts of a campaign!

    Other highlights…

    Turtle smuggling is thought to be a proving ground, a gateway into drug trafficking. Mexico is the principal transit country for 70 to 90 percent of cocaine entering the U.S., and the largest outside source of
    marijuana and methamphetamine.

    This, I did not know.

    Grupo Tortuguero continues its David-vs.-Goliath efforts to co-opt fishermen and volunteers from Baja’s fishing communities to monitor, tag and protect sea turtles. The group has dozens of sites along the peninsula and all have drug issues, ranging from trafficking to addiction. “I’ve interacted with fishers who were not ‘poachers,’ but were poaching for money to feed their habit,” says Nichols

    The article is interesting because it points out the similarities between sea turtle smuggling and drug smuggling, the use of young women, the co-opting of users to become dealers, the bribery of local officials, the organization to avoid capture, etc. Hmm…

  • Now we know where Juvenile sea turtles Hide

    Byoliveridley

    You see the hatchlings as they dig out of the nests all small and helpless and make a beeline towards the sea. You see the adult female as she comes back to lay her eggs. You see adult males when you go snorkeling , but the juveniles had kept a low profile, until now…

    Sea turtles’ mystery hideout revealed – LiveScience – MSNBC.com

    Once sea-turtle hatchlings hit the surf, they vanish for up to five years. Where the half-dollar-size tots spend these ‘lost years’ while ballooning to the size of dinner plates has been a mystery, until now.

    New research, published in the online edition of the journal Biology Letters, indicates the green sea turtles (Chelonia mydas) hide out in the open ocean, where they feast on jellyfish and other marine creatures.

    Turns out that they’ve been “hiding out” in the open ocean eating meat to augment their vegetarian adult diet. I have not seen the paper (reference below), but the study was based on an analysis of their shell content. Carbon and Nitrogen isotope analysis was used as a marker for diet and location.

    The ‘lost years’ of green turtles: using stable isotopes to study cryptic lifestages

    Kimberly J. Reich, Karen A. Bjorndal, Alan B. Bolten

    Archie Carr Center for Sea Turtle Research, Department of Zoology, PO Box 118525, University of Florida, Gainesville, FL 32611, USA

  • |

    Tuesdays with Turtles – Wednesday Hook Edition

    Byoliveridley

    WWF – Fishing Technology That’s Letting Turtles Off the Hook –

    Turns out that a small change in hook design can save a lot of turtles from getting caught in longline hooks. But the story’s not really about the shape of the hook. I’ve written about this before. The issue is rarely one of technology. The solutions have been developed and exist because a lot of work has gone into developing technological solutions. Implementation on the ground (or sea!) has lagged because it is much harder to effect change where it counts when you attempt to impose technology in a top-down fashion. Small scale fishers (new english here, to avoid the whole fishermen/fisherwoman/fisherperson nonsense, take out the gender specific suffix to every occupation describing verb! – Try it, it’s not weldman, or plumbwoman!) are in a world of hurt with declining fish stocks and widespread fisheries piracy by the so called “developed world”. Without developing and implementing the solution with the full participation of the people who have the most potential to be affected, the change will not be successful.

    What did the WWF do differently this time?

    Together with fishermen we are building a culture for sustainable fishing practices that will guarantee fish stocks in the long term

    They emphasized the people, not the solution. And the results were great, 90% reduction in turtle catch, >95% of the turtles caught were released safely, and the fish yields were not affected. Everyone wins, right?

    Good stuff. Those turtles are still endangered and we’ll run out of wild edible fish in 50 years, but hey, more like this and there’s a bit of hope.