Turtle excluder device

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A loggerhead turtle escapes from a fishing net through a TED.
A loggerhead turtle escapes from a fishing net through a TED.

A turtle excluder device or TED is a specialized device that allows a captured sea turtle to escape when caught in a fisherman's net.

Sea turtles are occasionally caught as bycatch by commercial shrimp fishers. These fishing boats commonly use a process known as bottom trawling to catch large amounts of shrimp, along with other marine organisms. When a turtle gets caught or entangled in a trawl net, it becomes trapped and is unable to return to the surface. As sea turtles are air-breathing creatures with lungs, they eventually drown.

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[edit] Mechanism

The use of the devices ideally allow all by--catch larger than ten centimeters (10 cm.) to escape the nets unharmed. This selectivity is achieved by metal grids integrated into the trawl net structure. The grids act as a barrier for large creatures such as turtles from passing through the bars into the back of the net.

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Turtle excluder device

A small opening in the net is then available either above or below the grid so that the creatures that are stopped by the TEDs are allowed to escape the net, relatively unharmed. Targeted species such as shrimp however, are pushed to the back of the net. As a conservation measure, turtle excluder devices are very effective. The rate of turtle mortality due to shrimping has been found to decrease by 97% with the use of TEDs.[1]

[edit] History

Another turtle escapes through the excluder device.
Another turtle escapes through the excluder device.

TEDs were first developed in the 1970s by a fisherman called Sinkey Boone, seeking to reduce his by-catch. It was patented on April 26, 1988 by inventor Noah J Saunders of Biloxi, Mississippi.[1] By decreasing the number of unwanted fish and creatures caught in their trawl nets, fishermen could trawl longer with the same net ideally catching more shrimp. Some resistance to the use of TEDs has arisen from the belief that the use of the devices actually causes fishermen to lose shrimp and other targeted species.[2]

In 1987, the United States required all trawling shrimping boats to equip their nets with turtle excluder devices. As a follow-up two years after, the shrimp-turtle law was implemented. This required all countries that the USA was importing shrimp from to certify that the shrimp they shipped were harvested by boats equipped with TEDs. Countries that cannot guarantee the use of the escape devices were banned from exporting shrimp to the USA.[3]

In 1996, the Indian government proposed legislature for the requirement of modified "indigenous" TEDs, which they called TSDs (Turtle Saving Devices) to be used by local fishermen. This was a response to the declining olive ridley population that were nesting in beaches such as in Orissa. The modified TSDs were similar to standard TEDs except for having fewer bars. This resulted in the increase of the distance between each pair of bars to ensure that bigger specimens of shrimp and fish were able to pass through the TSD and into the net.[4]

[edit] Failings and drawbacks

While turtle excluder devices have been relatively successful in lessening sea turtle casualties as by-catch, they still have a few failings and drawbacks. It has been acknowledged that the larger sea turtles, primarily large loggerheads and leatherbacks are too large to fit through the escape hatches installed in most TEDs. These turtles remain trapped within the net and perish. U.S. legislation introduced in 2003 has attempted to address this issue by increasing the size of the escape chutes in the devices.[3]

[edit] References

  1. ^ Turtle Excluder Devices (TEDs). Fisheries: Office of Protected Resources. U. S. National Oceanographic Atmospheric Administration (2007). Retrieved on 2007-09-01.
  2. ^ Lee, Scott (1999). Ancient Sea Turtles: Stranded in a Modern World. USA: Sea Turtle Restoration Project. 
  3. ^ a b Turtle Excluder Device (TED). Wildlife: Issues Facing Wildlife. The Humane Society of the United States (2007). Retrieved on 2007-09-01.
  4. ^ Behera, Chitta (September 2000). "Towards Averting the DoomÕs Day Imminent for Olive Ridleys: Indigenizing the Turtle Excluder Device and Reforming the Gillnetting Practice along the Orissa Coast of India". Proceedings of the 19th Annual Symposium on Sea Turtle Conservation and Biology 19: 215-216. NOAA Technical Memorandum NMFS-SEFSC-443. 

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