Robot sea turtles for ocean Safety

Where I’m a day late and a dollar short. It turns out that the Mediterranean sea is awash with plastic and most of the loggerheads there have swallowed plastic bags. So, the next time you’re out looking for loggerhead nests and find one in which all the eggs have been double bagged, do not be surprised! Now. if they start swallowing egg cartons…

Mediterranean drowning in a hidden sea of plastic rubbish – Independent Online Edition > Europe

A recent study of the endangered loggerhead turtle off Spain’s Mediterranean coast found that 75 per cent of them had swallowed plastic bags. Mr Rodriguez said: “We have to understand the sea is not a tip; it will constantly return to us what we throw in.”

Seriously, plastic bags need to go away.

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

  I have written about turtle excluder devices (TEDs) and how they save adult turtles lives previously. So, this story is an utterly avoidable tragedy brought about by the lack of implementation of laws regulating the use of TEDs.

The death of hundreds of Olive Ridley turtles along the Paravada coast in December 2007 had occurred due to failure of the trawlers to install the mandatory turtle excluder device. Lab tests conducted at Andhra University and Veterinary Biological Research Institute, Hyderabad ruled out the largescale death of the endangered species due to consumption of toxic contents discharged by industries located nearby or on account of rise in the seawater temperature.“We didn’t find any abnormal pollution levels. The washing ashore of carcasses was not a localised phenomena as dead turtles were found all along the coast up to Srikakulam during the year-end – the breeding season,” P.J. Vijaykar, Divisional Forest Officer told The Hindu on Wednesday.

The Hindu : Andhra Pradesh / Visakhapatnam News : Olive Ridley death riddle solved

Andhra Pradesh was supposed to be a success story with the TEDs. This from an article by Kartik Shanker, one of SSTCN’s founding members…

In India, the parallel cases of Orissa and Andhra Pradesh demonstrate how a TED programme should not (and should) be implemented. In Orissa, the polarization between the fishing community and conservationists has prevented the introduction of TEDs, while in Andhra Pradesh, TEDs were introduced by the state Fisheries Department with appropriate demonstration and training programmes (see Shanker and Pilcher, 2003).

So, this occurrence in Andhra Pradesh is quite disheartening and speaks to the large gaps that lie between legislation, policy and implementation in India.

Cross Posted at SSTCN

Tags: OliveRidley, Sea Turtles, SSTCN

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!

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.