Category: sea turtles

Tuesdays with Turtles – Why Adult Turtles Die so You Can Eat Fish

An interesting paper featuring a North Carolinian turtle researcher Larry Crowder from Duke University:

Blackwell Synergy – Conservation Biology, Volume 21 Issue 1 Page 79 – February 2007 (Full Text)

Abstract: Although some sea turtle populations are showing encouraging signs of recovery, others continue to decline. Reversing population declines requires an understanding of the primary factor(s) that underlie this persistent demographic trend. The list of putative factors includes direct turtle and egg harvest, egg predation, loss or degradation of nesting beach habitat, fisheries bycatch, pollution, and large-scale changes in oceanographic conditions and nutrient availability. Recently, fisheries bycatch, in particular bycatch from longline fisheries, has received increased attention and has been proposed as a primary source of turtle mortality. We reviewed the existing data on the relative impact of longline bycatch on sea turtle populations. Although bycatch rates from individual longline vessels are extremely low, the amount of gear deployed by longline vessels suggests that cumulative bycatch of turtles from older age classes is substantial. Current estimates suggest that even if pelagic longlines are not the largest single source of fisheries-related mortality, longline bycatch is high enough to warrant management actions in all fleets that encounter sea turtles. Nevertheless, preliminary data also suggest that bycatch from gillnets and trawl fisheries is equally high or higher than longline bycatch with far higher mortality rates. Until gillnet and trawl fisheries are subject to the same level of scrutiny given to pelagic longlines, our understanding of the overall impact of fisheries bycatch on vulnerable sea turtle populations will be incomplete

Adult sea turtle killing by humans occurs due to

  1. Harvest, killing them deliberately for food
  2. Incidental bycatch in fishing nets
  3. Habitat loss

The paper focuses on long line fishing and its effects on turtle mortality. So, if like me, you’re not a fisherperson, what is long line fishing and what are some other kinds of fishing techniques that have effects of sea turtles? Well, the Duke Project GloBal research team on studying bycatch has a nice primer. Some highlights:

  1. Longlines: As the word suggests, longlines are very long (>10 km) lines of 2000+ individually baited hooks that drift close to the surface and are used to catch tuna, swordfish, halibut, etc. Crowder’s paper suggests that while each individual longline hook has low probability of catching a turtle, because of their number and ubiquitousness, they catch many many turtles.
  2. Gillnets: These are giant rectangular mesh nets, either stationary or drifting, that catch marine life indiscriminately. There’s not much that can be done by way of reducingsea turtle catch in gillnets, except monitoring, observation and just using less of them
  3. Trawls: Big funnel shaped bags that catch fish. Bottom trawling fishing boats used to, and still catch turtles at an alarming rate. Trawls are now (at least in the U.S and other “developed” countries) required to be outfitted with Turtle Excluder Devices (TEDS) to let turtles swim to safety.
  4. Purse Seines: These are weighted on the bottom and float at the corners. They are indiscriminate, and especially hard on dolphins. It appears that mitigation efforts aimed at reducing dolphin mortality have the unintended effect of increasing sea turtle catch. Battle of the cute species!!

Take home message? Catching fish causes a lot of turtles to die. While trawl fishing is the worst culprit, it is also the most studied and the technique for which a viable mitigation strategy exists. THe other kinds of fishing are less studied, and there is precious little that can be done to avoid sea turtle bycatch.

Happy fishing!

Tuesdays with Turtles – Poaching in Mexico

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…

Tuesdays with Turtles – Travel Edition

sm_mapping.jpgIt’s travel all the time for sea turtles. Of course, the great turtle race is finally on, and windy’s in the lead, my pick billie’s in second place, a mere 30 miles behind. There’s a new turtle in the race, Colbertia, named in honor of Stephen Colbert, in third place.

Anything that gets turtles some attention is good.

But this is only a 500 mile sprint. PBS’ nature series had a one hour documentary on an 8000 mile, one plus year journey of a loggerhead turtle from her juvenile feeding grounds in Mexico to her adult breeding ground in Japan. It’s great to spend an hour at that close proximity to a turtle. But to me, the other animals, the dolphin pods, the giant fish swarms, the hammerhead sharks, the other sharks, the jelly fish, those little fish that eat parasites off the turtles and sharks kinda stole the show. There is something about thousands of animals of the same species doing something in concert. 

Anyway, nothing more to say, except that 8000 miles is a long way at a mile an hour. I don’t think any of us can appreciate the mindfulness and sense of purpose (do turtles have these qualities, or do they just keep on chuggin’?), not to mention the huge amount of luck it takes to get it done.

Bonus Turtle Coverage – The Great Turtle Race

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 – Gahirmatha Arrribada Hatchings

In case I forgot to mention, the Olive Ridley arribada started during the 2nd week of February, so about 50 days later, here they are, the “millions” of hatchlings.

The Hindu News Update Service

Olive Ridley hatchlings emerge in Gahirmatha

Kendrapara (Orissa), April 10. (PTI): Millions of tiny olive ridley sea turtle hatchlings are now emerging out of nests at the Gahirmatha beach in Orissa’s Kendrapara district, wildlife officials said on Monday.

The eggs laid by thousands of adult females in the Nasi-2 and Babubali islands in the Gahirmatha marine sanctuary have began to hatch over the last two days, they said.

Wildlife officials stationed at the nesting grounds were witness to the phenomenon, but tourists and researchers were not allowed into the unmanned territory close to the Wheeler’s island where a defence test range is located.

India’s intermediate range nuclear-capable missile Agni III is likely to be test fired from there some time this week, defence sources said.

You know what, the fact that this area is under close military supervision because of India’s grandiose missile dreams may not be sucha bad thing (sacrilege!!!). The area is under so much development pressure that even military operations are better than the alternative.

For more about the Gahirmatha area, visit the official website. At this point in time, the Arribada is very tourist unfriendly, and there are few, if any volunteering opportunities. I will keep any eye open for changes

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Tuesdays with Turtles – Must See TV Edition

PBS is showing a nature film following a loggerhead turtle on a looooooong journey.

Nature . TV Schedule | PBS

Voyage of the Lonely Turtle
Sunday, April 15, 8:00pm
CHANNEL 4 (UNC-TV)

F. Murray Abraham narrates this account of a 30-year-old female loggerhead turtle’s journey from Mexico to Japan (its birthplace) to lay eggs. During the yearlong trip (travel speed: 1mph), she passes an array of marine creatures, including blue whales.

Here’s a press release on the show, sounds great, don’t forget to watch (or record!): April 15th at 8:00 PM.

Tuesdays With Turtles – Hometown Edition

I grew up in Chennai and worked with the Students’ Sea Turtle Conservation Network in the mid ’90s. It’s nice to see an article on them in the city’s biggest newspaper.

The Hindu : Tamil Nadu / Chennai News : Olive Ridley hatchlings go home

CHENNAI: Scores of newborn Olive Ridley turtles entered their natural habitat — the sea — under the watchful eyes of conservationists at Elliots Beach, Besant Nagar, here early on Sunday. Conservationists said nearly 75 eggs hatched on Sunday alone and most of the young ones were safely released into the waters. But about 25 eggs reportedly did not hatch and some were stillborn. Volunteers of the Students Sea Turtle Conservation Network (SSTCN) annually collect Olive Ridley turtle eggs from the Besant Nagar coastline upto Neelankarai, a fishing village beyond Tiruvanmiyur. The eggs are then taken to a hatchery at Oorurkuppam, a fishing village located behind the Theosophical Society premises. It takes 45 days for the young ones to hatch.

In Chennai, and most of South India, the adult sea turtles are not poached, only the eggs. Also, it is not possible to just secure the nest with “do not poach” notice! So the eggs need to be relocated to a hatchery where they’re re-buried. For more on sea turtle “management” in India, I would suggest visiting Kartik Shanker’s excellent website.

Tuesdays with Turtles – Navigation

If you did not know already, sea turtles tend to nest on (or close to) the beaches they were born at. It is known that they use the Earth’s magnetic fields to navigate. Here’s an article on the navigational natations (I strain to alliterate at times, but natation means swimming!) of the Green Turtle.

ScienceDaily: How Do Marine Turtles Return To The Same Beach To Lay Their Eggs?

I flagged this article not because it tells us much new, but just adds some nuances to sea turtle navigation.

The study has shown that the marine turtles’ navigation system allows them to maintain their course towards the egg-laying site wherever they find themselves. It is almost as if they were equipped with a compass pointing towards the beach in question. So they can correct any deflection they are subject to: transport by boat, ocean currents… But, unlike human navigators, they are not able to correct for ocean drift in plotting their course. So the movements recorded by the satellite are a combination of deliberate action by the turtles and the effect of currents. So it appears that the turtles’ navigation system is relatively simple and may cause them to be wander at sea for long periods during adverse ocean conditions. One turtle released 250 km from its egg-laying site on Europa traveled more than 3 500 km in two months before returning there!

Well, that’s interesting, if not surprising. It’s one thing to have a magnetic bookmark of a destination in your head (pretty wonderful thing, I wish I had it!) and swim continually towards this destination. It’s quite another thing to keep track of complex parameters like ocean drift and keep correcting continuously.

In essence, what they’re saying is that turtles home in on their destinations, but don’t always take the shortest way in because they tend to drift and not correct for this drift dynamically. It is not evolutionarily necessary because turtles probably do not get thrown way of course often enough that evolving even more sophisticated navigational systems (Garmin?) would provide a significant enough survival advantage.

In the Mozambique Channel, between the east coast of Africa and Madagascar, on the beaches of the French Islands of Europa and Mayotte, they caught turtles at the beginning of their egg-laying cycle, so that the animals were strongly impelled to return to this area to complete their cycle. After having Argos transmitters fitted to their shells in order to satellite track their return journey to the beach, the animals were released in open sea, several hundred kilometers from the egg-laying site.

Now that’s just mean! Imagine being kidnapped, tagged and released many miles away from home, and having to find your way back. Apparently, these turtles did it. Man, that would be such a cool navigational aid to have, quite a party trick!

Tuesdays with Turtles – Outback Edition

flatback-kp.jpgWell, since this blog gratuitously takes its name from a sea turtle, it’s only fair that there needs to be a turtle post at least once a week! Why Tuesday? Because it alliterates. Why not Thursday? Because apparently, Tuesday’s the day that you do things with other things, ask Morrie.

I confess to knowing very little about the flatback. It’s only found around Australia and is listed as threatened. This news item caught my attention (for obvious reasons)

Turtles may fall victim to Australian gas project – International Herald Tribune

The peak nesting season is just drawing to a close for the flatbacks, a threatened species of sea turtle found only in Australia, when thousands of palm-sized hatchlings emerge from eggs buried under the sand and race to the sea. Every second counts: Between them and the ocean lies an army of hungry predators: lizards, dogs, foxes and gulls. Most of the turtles will never taste saltwater.

Development is another threat. Until now, the flatbacks could find some respite off the coast west of here, on Barrow Island, one of the country’s oldest nature reserves. But now environmentalists say that Barrow’s flatbacks may be among the victims of a plan by the oil giant Chevron to use Barrow Island for a roughly $8.6 billion project meant to supply natural gas to Japan and other energy-hungry nations.

“The environment is being made to pay for a poor business development model,” said Chris Tallentire, director of the Conservation Council of Western Australia in Perth.