You'd think sea turtles would have enough problems in this world, what with being born essentially helpless, having a long and predator-filled trek from the nest where they hatched out to sea, and occasionally being eaten by mako sharks once they've managed to grow big enough to be safe from most other predators. Human encroachment on their nesting sites, overhunting, and low hatchling survival rates have conspired to reduce populations to endangered species status.
And now in addition to all that, I find out someone has gone and invented a turtle excluder device; a device whose sole purpose is to make these vulnerable, put-upon ancient reptiles feel unwanted. Some species just can't catch a break. After little more research, however, I found that the turtle excluder is for the turtle's own good. You see what they're being excluded from is trawling nets, which can capture turtles underwater, preventing them from surfacing for air. A sea turtle can hold its breath for about an hour and a half (thanks to its efficient, cold-blooded metabolism), but trawling nets stay down for much longer than that.
Bottom trawling is a very efficient and widely popular method for catching bottom-dwelling creatures such as shrimp. Simply toss a weighted, tube-shaped net overboard, chug forward slowly, and haul up a net filled with delectable shellfish. Unfortunately, more creatures than just commercially valuable shrimp are found running around on the ocean floor, and the trawling nets aren't picky about what they scoop up. Starfish, rays, crabs, bottom-feeding fish, and sea turtles are all routinely caught in the trawling nets as well, and referred to as by-catch. By-catch creates two problems by wasting valuable shrimp space in the net, and accidentally killing enormous numbers of other creatures (up to fourteen pounds of by-catch can be discarded and wasted for every pound of shrimp). From a conservation standpoint, bottom trawling is comparable to strip mining or clear cutting.
In the 1970s, a fisherman from Georgia got tired of hauling up so much by-catch just so he could throw it back overboard, and invented the first turtle excluder device for his trawling nets. A typical turtle excluder is a large metal ring with a set of metal bars across it that is attached to the neck of a trawling net at an angle of about 40-60 degrees. The excluder blocks large animals such as sea turtles from entering the net, being pushed out into an escape hatch, while allowing smaller animals, such as the desired shrimp, to pass through. By 1990, US law not only required the use of turtle excluders on trawlers in the US, but also required any foreign imported shrimp to be caught using them as well.
The turtle excluder sounds like a win-win proposition, the fishermen waste less time hauling up unwanted catch, and endangered turtles (and other unwanted large creatures) get to escape from the nets. According to US government studies, turtle excluder devices can reduce accidental turtle captures by an incredible 97%, and other by-catch up to 60%. It also allows trawlers to legally continue fishing in areas with high sea turtle populations, after studies showed that they were effective. On the surface, this sounds like a great deal for fishermen.
Unfortunately, some fishermen believe that the excluders reduce their shrimp catches as well (although government studies claim the opposite), and others simply don't like being told what to do. Although turtle excluders are required by US law, it's a difficult law to enforce. Steep fines can be charged if caught, but there is little that can be done to monitor fishermen who modify them or neglect to use them at all.
The current regulations require the use of TEDs on all shrimp trawlers 25 feet or longer in offshore waters in the Atlantic from May 1 through August 31 and in the Gulf of Mexico from March 1 through November 30. Off shore vessels less than 25 feet and all vessels in inshore waters must use TEDs or limit the time the nets are towed to 90 minutes from March 1 through November 30 in the Gulf.†
http://www.nmfs.noaa.gov/pr/species/turtles/teds.htm
http://www.hsus.org/wildlife/issues_facing_wildlife/turtle_excluder_device_ted.html
http://www.bullfrogfilms.com/guides/astguide.pdf
http://www.fao.org/fishery/equipment/ted (good picture)
http://www.seagrantfish.lsu.edu/management/TEDs&BRDs/teds.htm
† http://library.thinkquest.org/11137/teds.html