By Jennifer Balmer
Each summer, leatherback sea turtles (Dermochelys coriacea) migrate thousands of kilometers from their tropical breeding grounds to feed in cooler waters. Yet how the animals know when to begin their long journey back south at the end of the season has mostly remained a mystery. New findings, to be published in an upcoming issue of theJournal of Experimental Marine Biology and Ecology, suggest thatleatherback sea turtles may be able to sense seasonal changes in sunlight by means of an unpigmented spot on the crown of their head—known as the pink spot (pictured). Researchers conducted an examination of the anatomical structures beneath the pink spot and found that the layers of bone and cartilage were remarkably thinner than in other areas of the skull. This thin region of the skull allows the passage of light through to an area of the brain, called the pineal gland, that acts as biological clock, regulating night-day cycles and seasonal patterns of behavior. The authors suggest that the lack of pigment in the crowning pink spot and thin skull region underlying it act as a “skylight,” allowing the turtles to sense the subtle changes in sunlight that accompany changing seasons, signaling them to return south when autumn approaches.
By CB Online Staff
Puerto Rico is posting record numbers of leatherback turtle nests along the island’s coastline this year as the government steps up efforts to protect the endangered species.More than 1,700 nests of the world’s largest turtle species have been identified so far this year (just halfway through the season), putting Puerto Rico well ahead of last year’s 1,386 nests, the largest amount in recent history.
While the undeveloped stretch of coastline between Toa Baja and Dorado has seen an increase in nests amid tougher protection efforts, beaches around the offshore island towns of Culebra and Vieques are home to fewer nests this year, according to the Department of Natural & Environmental Resources.
The first leatherback nest of the season was pinpointed in the heart of the Isla Verde tourism zone at the edge of the capital city San Juan in February. Hundreds of additional nests have been located along the sandy strands within close range of the metro area, including some 300 in the Dorado area.
New conservation efforts, including cordoning off nests, and more volunteers monitoring beaches, are helping shore up the numbers of the federally endangered species in Puerto Rico. There were 1,369 nests spotted in 2011 and 1,359 in 2012. The nearly 1,390 nests in 2013 represented some 68,000 baby turtles, but only one out 1,000 leatherback turtles survive to become an adult.
Natural resources officials have noted that that turtles are favoring new nesting sites instead of traditional locations such as Culebra and the northeast coast, which became a protected area last year.
Puerto Rico has the highest number of leatherback turtles in the U.S. and is second in the Caribbean after Trinidad and Tobago.
The turtles coming as far away as Canada and northern Europe to nest. They can weigh up to 2,000 pounds (900 kilograms) and can measure up to 7 feet (2 meters) long. An estimated 26,000 to 43,000 female turtles nest annually across the world, down from some 115,000 in 1980.
For decades, the IUCN Marine Turtle Specialist Group has debated the utility and appropriateness of single global listings on the Red List of Threatened Species for widely distributed, long-lived marine turtle species. The main disadvantage of global listings is that they fail to describe and assess wide variations in marine turtle population dynamics, extinction risk, and conservation status across subpopulations, so can lead to misleading and confusing results. Today marks an important breakthrough for marine turtle Red List assessments. The IUCN Red List Authority has published the new leatherback Red List assessments, which, for the first time, include subpopulation-level listings—not simply a global listing. This is the first time that any marine turtle species has been officially assessed, globally, to the subpopulation level, and sets an important precedent for other marine turtle Red List assessments, as well as red listing of other widely distributed, long-lived species, such as sharks, marine mammals, and seabirds.
These assessment results reflected the wide variation in leatherback subpopulation status, accurately highlighting subpopulations that have declined greatly over time, as well as those that are small and /or geographically restricted, and merit Critically Endangered status. These subpopulations require effective protection and reduction of threats to ensure their future existence.
Globally, leatherback status is now Vulnerable. East Pacific, West Pacific, Southwest Atlantic, and Southwest Indian Ocean subpopulations were listed as “Critically Endangered,” Northwest Atlantic leatherbacks were listed as “Least Concern,” and Northeast Indian Ocean and Southeast Atlantic subpopulations were listed as “Data Deficient.”
We are working on Red List updates to several other marine turtle species using this subpopulation approach, as well as other improvements to how we interpret and apply Red List criteria to marine turtle assessments.
By By Kimberly Castillo
Story Created: Nov 16, 2013 at 9:13 PM ECT
Story Updated: Nov 16, 2013 at 11:53 PM ECT
TRINIDAD’S leatherback turtle population is in rapid, continuous decline, according to the latest report by leatherback sea turtle expert Dr Scott Eckert from the United States.
In the October 2013 report, Eckert noted that despite strong growth in the population in the ’90s as well as progress in protecting turtles in their nesting beaches, the current status of the Trinidad nesting colony is alarming.
This rapid downward trend, which has been observed since 2006, can be traced to the high mortality of leatherbacks due to gillnet fishing.
If gillnet mortality is not eliminated, Trinidad’s leatherback population will continue to decrease, Eckert reports in his latest document, “An Assessment of Population Size and Status of Trinidad’s Leatherback Sea Turtle Nesting Colonies”.
Eckert based his findings on data collected throughout the ’90s up until 2012.
“The rapid decline trajectory of Trinidad’s nesting population is cause for alarm,” said Eckert, director of Science at the Wider Sea Turtle Conservation Network (WIDECAST).
WIDECAST is a network of marine experts, conservationists and managers from 40 countries and territories.
Eckert said all studies indicate the decline in the leatherback population is local to the Trinidad colony, since the North American populations continue to increase.
Every year, it is estimated that more than 3,000 leatherbacks are caught in gillnets off the coasts of Trinidad.
The impact gillnet fishing has on reproductive turtles is a serious cause of concern—annually more than 1,000 egg-bearing turtles get entangled and drown or are killed while fishermen try to save their nets.
“Particularly alarming about the current population trajectory and the impact of fishing mortality on the population is that the source of mortality is directed at reproductive adult turtles. Reproductive-age sea turtles are the most sensitive component of any population, and their destruction has the greatest impact [on] population stability,” writes Eckert.
If gillnet fishing continues as it is today, the decline in Trinidad’s leatherback population will mirror the destruction of the world’s largest leatherback population in the Eastern Pacific, he warned.
In 1979, the leatherback population on the pacific coast of Mexico reportedly exceeded 75,000, but by 1995 the number dwindled to 1,000 and is believed to be even lower today.
Eckert reports the main cause for the decimation of the population was the introduction and deployment of large-scale gillnet fishing for swordfish in the 1980s in areas off Chile and Peru, which were also foraging grounds for the leatherback turtles.
In the report, Eckert said there have been efforts since 2005 to have alternative methods employed that can reduce entanglement by 65 to 90 per cent, and mortality by 90 to 100 per cent with no reduction in the fisher income.
But adoption of these methods has been slow, he reported.
“In the absence of widespread use of fishing methods that do not kill turtles, high sea turtle mortality within the coastal gillnet fishery will continue, with devastating results to the turtles,” he noted.
People’s National Movement councillor for Toco/Fishing Pond and former fisherman Terry Rondon said considering that the “a la vive” fishing method is one of the most productive fishing methods which does not endanger sea turtles, the Government should assist fishermen in adopting this alternative by supplying the fishers with live bait.
The availability of live bait is an obstacle to switching to “a la vive” or hook-and-line fishing.
Failing this, Rondon suggested Government provide incentives to fishermen to keep them out of the water during turtle-nesting months. This includes compensating fishermen for lost income during those months. To prevent fishermen from “outsmarting” this system, Rondon said the Government should establish legislation which would include penalties for those who continue to set nets in sea turtle-foraging grounds during the nesting months.