Boat-Based Activities, Dolphin-Watching Industry Threaten Bocas Dolphins
A new study suggests that bottlenose dolphins in Panama’s Bocas Del Toro archipelago should be classified endangered. According to the researchers, about 80 dolphins in the area do not interbreed with other species of Caribbean bottlenose dolphins.
Tursiops truncates or the common bottlenose dolphins are the most common members of the oceanic dolphin family. They are currently the dolphin species with the least concern on the Red List of Threatened Species in the International Union for Conservation of Nature. Bottlenose dolphins inhabit seas that are warm and temperate and usually stay in groups of about 10 to 30 members. Their average size is 10 to 14 feet while the average weight is 1,100 pounds.
Aquarium shows star bottlenose dolphins because of their charismatic and intelligent personality. The audience is likely to be captivated by their friendly appearance and permanent smile while performing complex tricks. As natural swimmers, these dolphins have more than 18 miles per hour of swim speed, communicate with each other using squeaks and whistles, and are experts of echolocation. Echolocation is a biological sonar that allows certain animals to reveal a location or a target. Bottlenose dolphins were also once hunted for meat and oil.
In the latest study, the researchers found that the Bocas dolphins were founded by a small dolphin family a few thousand years ago. They do not have any meaningful exchanges with the nearby dolphin population 35 kilometers away from Costa Roca. They avoid murky green waters and prefer to be in cloudy, mangrove-surrounded waters. Their current habitat is shallow, protected from sea waves, and they do not have any large predators.
However, their lack of ability to interbreed with other dolphin populations threatens their long-term survival, especially with the increasing number of the local boats traveling near their habitat. About seven bottlenose dolphins in Bocas were killed in 2012. Other incidents affecting the dolphins, such as boat noise, boat strike injuries, and fishing net entanglements were also reported.
“Our results indicate that the population of dolphins in Bocas Del Toro is genetically isolated from other populations in the Caribbean, and given the high impact of boat traffic on the animals, we suggest that its conservation status be changed, at least at a local level. Conservation priorities are largely dependent on the IUCN conservation status of the species,” said Dalia C. Barragán-Barrera of the Universidad de Los Andes in Columbia and the lead author of the study.
In order to find out the reason behind their isolation, Barragán-Barrera obtained skin samples from 25 Bocas dolphins. The analysis revealed that the dolphins shared the same haplotype, a group of genes inherited from a single mother. Other dolphins in the Caribbean were not found with haplotype genes, which suggested the isolation and adaptation of the Bocas dolphins.
Researchers said that pressure on the dolphin-watching industry and awaiting threats to the dolphin led the International Whaling Commission to create four recommendations to the Panama Government. These recommendations were designed to protect the dolphin population but the industry continues to grow and affect the Bocas dolphins.
Generally, bottlenose dolphins are not endangered. But subspecies of these dolphins located in many regions, such as in the Mediterranean Sea, the Black Sea, and Fiordland in New Zealand are currently vulnerable to endangerment. Several environmental changes also threaten the long-term survivability of specific populations of bottlenose dolphins.
- According to WDC at the Scottish Dolphin Center, there is a small population of bottlenose dolphins in Moray Firth consisting of more than 190 members. This subspecies of bottlenose dolphins has been under the Special Area of Conservation since 2005 to protect their habitat. They are currently being threatened by human-related activities such as chemical pollution, fisheries interaction, large marina development, and exploration of oil and gas.
- In a study published in 2008, the subpopulation of bottlenose dolphins in the Mediterranean Sea was found vulnerable to numerous factors such as ecological changes, fisheries interactions, and degradation of the region. The conservation status of the Mediterranean subpopulation is vulnerable, according to IUCN.
- In the Red List of IUCN, the Black Sea subpopulation of bottlenose dolphins has an estimated 1,000 members, which were live-captured since the 1960s. The subpopulation is currently endangered due to degradation of the Black Sea as the result of overfishing and habitat destruction.
- The Fiordland subpopulation of bottlenose dolphins in New Zealand is classified as critically endangered. The population of the subspecies has 205 members, of which 123 are mature dolphins. The major threats to them are the disturbances from the boat-based tourism in Milford and Doubtful Sound, increasing amount of freshwater from the hydroelectric power in Doubtful Sound, and reduction of food sources in the area due to environmental degradation and overfishing in Fiordland.
Shark Bay in Western Australia has one of the largest populations of bottlenose dolphins. The region also has one the largest seagrass meadows in the world, essential to many marine life forms such as the dugong, dolphins, sharks, rays, and turtles. The protective status of Shark Bay also provides a secure home for about 11,000 dugongs and increasing numbers of humpback whales and southern right whales.
[리서치페이퍼=Ralph Chen 기자]