Posted by Zabar Yunus On 0 comments
" "

Although the number of obstacles that sea turtles face during these stages of their lives is fewer, there are still many to be overcome. As sea turtles grow from subadults to adults the number of natural predators decreases. This is simply due to the fact that the turtles are growing larger, and the number of predators that can actually successfully prey upon them is fewer. Sharks and other fish continue to prey upon them, but by the time a sea turtle reaches full mature size these attacks seldom result in death for the turtles. Females often emerge from the sea to nest with flippers, both rear and front, mangled or completely missing, which can greatly limit her ability to nest. These injuries are most likely the result of an attack from a large shark, and can also prevent a male from successfully mating. Sea turtles will eventually outgrow the majority of their natural predators. But there are two threats they cannot outgrow: disease and man.

Diseases do afflict sea turtles, but naturally occurring diseases – meaning diseases not enhanced by human activities – do not seem to occur with any great frequency or cause a large number of deaths. There is however one disease that is currently having a very adverse affect upon sea turtles, and will be discussed in more detail later in this section. Human beings are the second natural predator that sea turtles do not outgrow and our actions are causing mortality in sea turtles with great frequency.

Humans have harvested sea turtles for food consumption and for their shells and leather for various purposes
throughout history with seemingly little or no affect on their overall survival. But, the population of humans, and thus the areas that we inhabit, have been increasing through the ages. These increases, along with the non-selective fishing practices in use today, have placed additional pressure on the ability of populations of sea turtles to survive.

Historically sea turtle meat has been a primary source (and when fishing was poor, an alternative source) of protein for many coastal communities. Some communities still partly rely on sea turtles as a source of protein. The primary sea turtle dish that is consumed by humans today is green turtle soup, and a lot of this soup is prepared to satisfy foreign market and tourist demand. It is a luxury or novelty item, just as so many of the items produced using sea turtle shells and skins are. Until 1990, when the Mexican government placed a ban on the trade of sea turtle products, up to 50,000 sea turtles a year were slaughtered in Mexico alone for their skins and shells. Today it is estimated that tens of thousands of turtles are slaughtered each year for the production of luxury items such as boots, belts, purses and eyeglasses frames made from sea turtle parts. Thousands of sea turtles are also dying as so-called bycatch in the nets and on the hooks of fishermen each year.

Sea turtles breathe air and must surface regularly to survive. When they get caught in fishing nets or on fishing hooks, they drown. Modern fishing methods such as shrimp trawls, large nets drug behind boats, drift nets, and long lines, baited hooks stretching out great distances, inadvertently capture sea turtles. These turtles are wastefully discarded as by- (unwanted) catch, since they are not the intended quarry of the fishermen. An estimated 150,000 sea turtles were captured worldwide in fishing nets last year, with one-third of those being
caught in U.S waters. Numerous other non-targeted species suffer the same fate. Shrimp trawling has been identified as having the largest bycatch rate of all fisheries, representing 35 percent of the worldwide total for all fisheries combined. Shrimping in U.S. waters is responsible for close to 1.5 million metric tons of bycatch per year. Up to fourteen pounds of fish are destroyed and discarded for each pound of shrimp harvested in some shrimp fisheries. Therefore not only do these fishing practices place sea turtles at great risk; they threaten the biodiversity of the entire ocean. However, there is a simple and inexpensive, device that can be installed in the nets of shrimp trawlers that can greatly reduce these negative affects of the industry.

These devices are known as TEDs, or Turtle Excluder Devices. TEDs are metal grids that are sewn into shrimp nets and guide sea turtles and other unwanted bycatch out an escape hatch. U.S. government studies show that the proper design, installation, and use of TEDs can reduce the number of turtles killed by shrimping by 97% or more. Furthermore, TEDs reduce the bycatch of other marine organisms by up to 60%. TEDs are required on U.S. shrimp fishing vessels by way of a provision of the U.S. Endangered Species Act. The problem is in getting some fishermen to properly install, or use, a TED at all.

Like other provisions of the endangered species act, the TED provision is one that is very difficult to enforce. Many fishermen see the value of TEDs. TEDs were actually developed by a fisherman from Georgia in the 1970s to reduce bycatch and increase the time he could pull his net for shrimp. Still other fishermen contend that TEDs cause them to lose shrimp, and thus alter the TED in a manner that makes it ineffective in releasing sea turtles and other bycatch.

Pollution is the final threat from man that subadult and adult sea turtles must contend with. Unfortunately many humans view the ocean as an unlimited resource, and they exploit it by dumping pollution and trash into the sea. Materials such as plastic bags or congealed oil are often mistaken by sea turtles to be jellyfish, a common food source. When these materials are ingested by the turtles they either choke on them or in rare instances die of starvation because of their inability to digest the foreign object that is now obstructing their digestive tract. Pollutants invisible to the turtles are a very real threat to their survival as well.

A disease known as fibropapilloma is now affecting large numbers of sea turtles and as alluded to earlier it is not a naturally occurring disease. This disease is believed to be caused by a toxin, okadaic acid, which is produced by a microscopic bottom dwelling alga known as a dinoflagellate. These dinoflagellates are always present and producing this toxin, but runoff – primarily nitrogen and phosphorus – from land activities such as farming acts as fertilizer for the algae. Fibropapilloma does not directly cause death, but is instead responsible for the formation of tumors on the turtles. These tumors often form around the eyes and mouth of sea turtles
severely limiting their ability to locate and ingest food. Other fertilizing and toxic pollutants introduced into the ocean by man undoubtedly have an adverse affect on food sources of sea turtles. The dying off of turtle grass off the south coast of Florida is only one such example.

The End of  Turtle Education

Request a public education action kit
To order your free action kit, please contact the
Sea Turtle Restoration Project
PO Box 400, Forest Knolls, CA 94933
415-488-0370 or
email to seaturtles@igc.org

" "
Semoga artikel TURTLE PARTS 9: OBSTACLES FOR SUBADULTS AND ADULTS bermanfaat bagi Anda.

Jika artikel ini bermanfaat,bagikan kepada rekan melalui:

Post a Comment

Thanks for visit me...