Apex predators like sharks play an important role in regulating species dynamics in their marine ecosystems.
Blacktip reef sharks are known to be abundant in some parts of their range, yet pictures of a large number of the marine predators being sold openly at a fish market on the popular resort island of Phuket in Thailand have sparked outrage among environmentally conscious Thais and concerns among local conservationists.
Apex predators like sharks play an important role in regulating species dynamics in their marine ecosystems. In areas where the number of shark diminishes or their species distribution changes, manifest shifts take place in the composition of species and their abundance.
For instance, according to experts who relied on research conducted in some coastal areas of the United States, after the number of blacktip reef sharks declined sharply, the population of cownose rays, their main prey, began to increase with negative knock-on effects.
“Shifts in species abundance are not the only consequence of removing top predators, as habitats also can be altered. Hungry rays roaming the waters and hunting for food have the potential of uprooting seagrass at higher rates, leading to poorer quality nursery grounds for fish,” the conservationists noted.
“Additionally, bivalves are not only a food source for rays, but a filtration system for the ocean. Bivalves feed on phytoplankton that they filter from the water column, which helps maintain a high level of water quality. With the decline in scallops, clams and other bivalves, this filtration system is disappearing,” they went on to explain. “As a result, already stressed coastal areas could experience additional uncontrolled algal blooms and dead zones, damaging ocean ecosystems.”
Other experts dispute these claims, stressing that the presence of more cownose rays in an area would not be the cause of such cascades in an ecosystem.
What is not in dispute, however, is that marine predators like moderately sized blacktip sharks, whose name comes from the black coloration on the tops of their dorsal, caudal and pectoral fins, are vital for the health of marine ecoystems.These sharks are listed as near-threatened by the International Union for the Conservation of Nature (IUCN).
Yet in Thailand, they are not protected animals. Local fishermen, therefore, can hunt and sell them in markets freely. And so despite the outrage over the photos of them being sold in large numbers in Phuket, an island routinely dubbed “a tropical paradise,” there isn’t much that can be done.
“At this stage, the blacktip reef shark has not been classified as a protected animal,” explained Watcharin Rattanachoo, chief of the Phuket Provincial Fisheries Office. “I understand the photos may hurt people who love animals, but the fishing and selling of these sharks is not illegal in Thailand.”
Conservationists, however, are warning that if a large number of the sharks continue to be hunted without limits, eventually the predators will vanish from local waters, which could lead to the collapse of some of the country’s marine ecosystems.
“Blacktip reef sharks and many other sharks are not protected animals [in Thailand]. I’ve tried to push for this many times. I hope we can progress, especially for hammerhead sharks and leopard sharks, whose numbers are rapidly falling,” said Thon Thamrongnawasawat, an expert on marine life.
“Sharks are important to the ecosystem and the food chain. They are also important for tourism,” he added.