Tuesdays with Turtles – Lighsticks Kill

Following up on the fishing issues from last week, here’s word that lights used to lure tuna towards longline fisheries attract juvenile sea turtles as well.

Article – Science & Technology – Lightsticks may hold deadly attraction for sea turtles

RALEIGH, N.C. Longline fishermen use lightsticks similar to the glowing tubes that delight trick-or-treaters to lure tuna and swordfish to baited hooks. New research by University of North Carolina-Chapel Hill scientists suggests that for endangered sea turtles the lights may hold a fatal attraction.

Lab experiments by Ken Lohmann, a University of North Carolina biology professor and John Wang, a graduate who is now a research associate at the University of Hawaii and National Marine Fisheries, found that young loggerhead turtles in a tank tended to swim toward lights.

It’s well known that hatchling turtles on a beach will crawl toward lights as they try to find the surf. But researchers did not know whether juvenile loggerheads in the water shared that attraction. Young loggerhead and leatherback sea turtles, which are protected because of declining numbers, are inadvertently hooked during longline fishing.

Well, not so surprising, is it? Bioluminescence is a common enough phenomenon that especially at night, animals will be attracted to light as it can signal food. It’s tricky, but when you try to catch fish, tyou will catch other animals as well. So, when you change something about the way you catch fish, you need to study how it affects other endangered species…

Off topic, but it is ironic that I read this in the ocregister, which is a newspaper from Orange County, California. It reported on work done by UNC Chapel Hill, which is in Orange County, North Carolina.

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    Tuesdays with Turtles – Climate change and nesting patterns

    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.

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    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 – 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!

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    Tuesdays with Turtles – Right Flipperedness Edition

    Across a population studied by scientists, more turtles preferred to use their right rear flipper rather than their left when laying eggs.The result, published in the journal Behavioural Brain Research, is the first time a species of turtle has found to prefer one limb over another.The discovery adds to growing evidence that even lower vertebrates prefer to use one side of the body more often.Such preference is known by scientists as a “lateralised functional behaviour”, and it usually indicates that an animal's brain function is also lateralised, with one side of the brain dominating control of certain tasks.

    via BBC – Earth News – Turtles are ‘right-flippered’.

    Ha, just when you thought Tuesdays with Turtles was gone, it is Tuesday (here in Canada) and a sea turtle post. Turns out, leatherbacks, the biggest of ths sea turtles and critically endangered tend to be right flippered while on land and laying eggs. A slight predilection to right sidedness runs all the way down to reptiles. It is 54%-46%, which does not seem like much, but the report indicates that among humans, it is the same once you control for a cultural right hand bias!

    Anyway, got to love those sexy beasts, even if they’re right flippered, right Ned?