Sharp drop in nesting turtle numbers

DoE positive about long-term trend for sea turtles

DoE visiting scientist Joe Roche pulls a Green Sea Turtle hatchling from a nest in South Sound in November.

Despite threats from poachers, plastic pollution, coastal development and now sargassum seaweed, researchers remain optimistic about the long-term survival of the Cayman Islands nesting sea turtle population.

While the 406 nests recorded in the 2018 nesting season is significantly less than last year, the Department of Environment believes this is a temporary fluctuation. Research officer Janice Blumenthal said the longer-term trend, after two decades of monitoring turtle nesting, was extremely positive.

As long as Cayman Islands residents help to manage a growing range of threats, she expects that to continue.

“In 1998, with sea turtles nearing extinction in the Cayman Islands, we found a total of 15 turtle nests on Little Cayman and one nest in Cayman Brac. Surveys began on Grand Cayman in 1999, where we found just 23 turtle nests,” she said.

Numbers have been growing steadily since then, peaking last year, when a record 688 nests were recorded by researchers.

Ms. Blumenthal is unconcerned by the significant drop in turtle nesting over the past year.

“This decrease is in the context of an overall recovery of the local turtle nesting population and we have seen a strong upward trend. As our monitoring has been consistent, we are confident this is a true increase.”

She said it was natural to see fluctuations in nesting numbers and the DoE anticipates numbers will rebound in 2019 or 2020.

A group of Cayman International School students meet a Green Sea Turtle hatchling during one of DoE’s ‘turtle talks’ in November.

For the last 20 years, the DoE and a small army of volunteers have walked the island’s beaches, keeping tabs on the number of turtle nests each season. Despite encouraging increases in numbers, Ms. Blumenthal cautions that there is more work to be done.

She said, “It is important to note that each turtle nests multiple times in a single nesting season, and the overall number of green and loggerhead turtles in our nesting populations is still very low.”

She said the local nesting populations faced a wide variety of threats and would likely not survive without the efforts of DoE conservation officers who help guard nests from poachers.

Periodic invasions of large mats of sargassum weed, which washed up on Cayman’s beaches in large quantities this summer, also provide a new threat to nesting turtles.

“In addition to long-standing threats, we now add sargassum influxes to the mix. Sargassum deprives turtle nests of oxygen and can impede hatching. However, the biggest threat to nests during and after sargassum influxes is the use of heavy equipment on the beach to remove the seaweed, which can impact the nesting sites if equipment operators drive over them.”

Anyone who needs to clear a beach of sargassum is asked to seek permission from the DoE, which provides authorization for the use of heavy equipment, taking into account the location of active nests.

Another emerging threat to Cayman’s nesting turtles is plastic pollution, including discarded fishing line.

Ms. Blumenthal said DoE officers had encountered numerous examples of turtles, and many other marine species, trapped or killed by discarded plastics on Cayman’s beaches and in waters close to shore.

The department is also continuing to encourage beachside property owners to use turtle friendly lighting. Hatchlings, which orient themselves toward the sea by following the light of the moon on the water, can be disoriented by the glare of lights from coastal properties, and head inland.

Ms. Blumenthal said managing these type of threats was crucial to the survival of nesting sea turtles in Cayman.

“The turtle nesting recovery seen in the Cayman Islands over the past 20 years could continue. However, that will occur only [if] we do our part in mitigating the risks faced by this national symbol while breeding on our shores,” she added.

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