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

Byoliveridley

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!

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  • Tuesdays with Turtles – Hatcheries

    Byoliveridley

    A little old, but turns out that the WWF is establishing a hatchery for Olive Ridley sea turtles in Orissa.

    WWF-India comes with artificial hatchery for Olive Ridley eggs – Newindpress.com

    Large-scale destruction of Olive Ridley eggs at nesting sites in the State’s coast has prompted WWF-India to come with an artificial hatchery. It would also double up as a hatching protection centre. The artificial hatchery has been established near mouth of Rushikulya river where WWF-India staff have stored a large number of Olive Ridley eggs along with the arrangements for safe hatching. Last month alone, 116 nests were safeguarded and around 13,000 Olive Ridley eggs were stored in the artificial hatchery. Till end of the week, more than 2,000 eggs have hatched, chairman of WWF-India, Orissa State Committee Saroj Kumar Patnaik said.

    Hatcheries become necessary when the natural habitat can no longer be protected. The biggest advantage of a hatchery is the fact that once the eggs are relocated, they are now safe from poaching/predation. But, there are some disadvantages including the resources needed, the possible overcrowding effects if the hatcheries are not well designed, etc. Luckily, there are good resources available for building and managing a good hatchery. With the WWF’s funding and experience, I am sure it will be a very well managed hatchery.

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    Tuesdays with Turtles – Climate change and nesting patterns

    Byoliveridley

    Turns out that in Guyana, nesting patterns are changing. Different types of sea turtles are showing up, and earlier than they used to. The earlier part can be explained by climate change, but the species distribution? I am sure there are other factors involved including habitat loss, poaching, etc. Anyway, interesting story.

    Stabroek News

    The changing nesting patterns of endangered sea turtles in Guyana, is alerting environmentalists to the impact of climate change on these marine animals.

    The shell beaches in Region One have hosted thousands of nesting turtles over the years, and conservationists have been endeavouring to protect the turtles from heavy domestic use and from being traded.

    Project Coordinator of the Guyana Marine Turtle Conservation Society (GMTCS) Michelle Kalamandeen told Stabroek News recently that climate change is affecting the sea turtle population.

    According to Kalamandeen, in the 1960s the Hawksbill (critically endangered) and the Olive-Ridley (endangered) were our main nesting turtles, now the green turtles (endangered) and the leatherbacks (critically endangered) are mostly coming to nest on Guyana’s shores. The Pacific Leatherback is said to be now extinct and the Atlantic Leatherback is facing extinction.

    The change in the time period for nesting in Guyana, she said, may also be a significant sign.

    Usually sea turtles nest in Guyana from March to August every year. However, for the last three to four years, says Kalamandeen, the nesting pattern has shifted from mid-January to mid-July. This may have a significant impact on the hatchlings as food availability may be an issue for them.

  • Tuesdays with Turtles – Triumphant Return

    Byoliveridley

    So, blogging has been light this summer as Olive Ridley’s partner made her way to Canada and is settling in. Also, it is summer in BC and beautiful as hell, so the prospect of sitting down and typing on a computer with brains that are only half working, well, ain’t so hot! Also, Canada is just a much calmer place than the U.S. As I looked back at my many posts, most of them are bitter fulminations against American politics or the various shenanigans of the Emperor. Anyway, I am not under his rule any more, and while he’s gutting the Endangered Species Act as we speak, he will be history soon.

    While Canadian policy debates are equally interesting, they are generally civil in comparison, except the occasional kerfluffle where old white men want their female opponents to go back to making tea, charming…

    Anyway, I felt the blogging itch again and as always, it’s nice to get back with a story about turtles.

    Researchers say they have figured out why sea turtles that normally feed and breed in shallow water or on land will, very rarely, go deep sea diving: the reptiles are on reconnaissance.

    Sea Turtles Dive to Depths for Reconnaissance : Discovery News

    Leatherbacks have amazing diving capabilities and can get up to a kilometre below the surface. Why? for food, of course! More precisely, the promise of future food. Turns out that jellyfish (or jellyfish like animals) hang out in the deep during day time and surface at night. Leatherbacks go looking for them during the daytime down in the deeps so they can get them on the surface for dinner. It’s akin to you taking a leisurely walk around downtown looking for the perfect dinner spot.

    Interesting. As always, very fascinating and sexy creatures, and critically endangered.

    Expect more regularly scheduled blogging just in time for the late summer sweeps!

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    Turtles, Arribadas, Science, Policy and Implementation

    Byoliveridley

    turtle Read stuff like this (hat tip to my mom for telling me about this report she’d seen on TV in Madras), and you begin to doubt your utility as a scientist.
    IBNLive : Orissa turtles neck-deep in danger

    Nearly 3,000 Olive Ridley turtles have died off the Orissa coast this season. Beaches have become turtle graveyards.

    Orissa is one of the three places in the world where the Olive Ridleys come for their annual mass nesting.

    Mechanised trawlers are the biggest culprits for this slaughter. When the trawlers go to the sea, turtles are trapped in their fishing nets. The turtles are unable to disentangle themselves and suffocate to death.

    See the video report too. In her own breathlessly indignant style, the reporter explains the science behind turtle excluder devices (well known and established), the regulation expressely forbidding shrimp trawling close to the coast, especially during the arribada, the money set aside in the budget to purchase a few speed boats for the coast guard, who are well aware of the problem, so wot’s, uh, the deal?

    The investigative reports contradict each other, the first one linked said there was no patrolling, the second one gushingly praises the coast guard for vigorous enforcement and patrolling, so which is it? I need to find out, call on some old friends… But clearly, there are issues if net catch mortality is on the rise.

    The three pillars of any regulatory action are the science, the policy, and the implementation. The science here is very clear (though the US administration seems to not think so any more?), shrimp nets with turtle excluder devices cause decrease in mortality. The policy is clear, use these nets when shrimp fishing, and completely ban fishing activity during the arribada (the number of turtles in an arribada, 50000 in a night and perhaps 300000-400000 over the course of a week is staggeringly large, so, shrimp net or not, you’ll kill a lot of turtles just by being there).

    So, like anything else in India, where is the implementation? The people running the trawlers know they are illegal anyway, so they don’t bother with the TEDs. The owners of the trawling boats never face the consequences, only the poor hapless fishermen running the boats. No attempt is made to coopt the people being regulated, it is a top down “we tell you what to do” kind of situation where the law is selectively enforced, no explanations are given, the regulation may just be an excuse to get some kickbacks. The fishermen see the excluder device as an inconvenience as they are not shown how to use it. Some low level bureaucrat in charge of buying high speed boats for the state’s forest service either does not realize the importance of getting this policy on the road, or is on the take. You can pick any, or all of these reasons and you’ll see why just like most other things in India, the road to hell is paved with good intentions 🙁

    Why be a scientist and come up with cool new techniques to do things when you don’t pay equal attention to the implementation of techniques invented 20 years back? As a responsible scientist, I must look at policy and implentation with as much interest and passion as I look at the science – New career paths?

5 Comments

  1. Pingback: Tuesdays with Turtles - Lighsticks Kill « The Olive Ridley Crawl
  2. Pingback: 100s of turtles die in Andhra Pradesh « The Olive Ridley Crawl
  3. Pingback: 100s of turtles die in Andhra Pradesh « Students’ Sea Turtle Conservation Network

  4. i think you should have a little more information, and make the words a little more bigger.I realy could not see the words at all.So can you please email me a better copy thats all i ask for.

    my turtle is dying and i don’t know wat to do he is not eating none of the food we give him. We brought him home on June the 13 2009 at J&A’s 99 cent store for $8.99 i dont think that is a good store they only have chinease people working there and they can’t understand english at all that gets on my nerves i hate chinease people please read this message.

    love,
    A’ Sha
    Harris

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