East coast threatened by coral-eating star fish

As the world celebrated World Oceans Day on June 8, environmentalists here are concerned about a rapidly growing coral-eating startfish, in the East coast.

Marine naturalist Prasanna Weerakkody issued this warning after spotting an increased population of the Crown of Thorn Starfish in certain areas of the Coral Reef in Pigeon Island, in Trincomalee.The Crown of Thorn Starfish (COT) is a large sea starfish that lives and preys on live coral, destroying them in the process. They have an interesting way of feeding on the corals by turning inside out their gastric sac (stomach) through their mouth, covering their food with the sac and digesting it with enzymes.

Mr. Weerakkody had observed 28 large Crown of Thorn starfish in a southern section of Pigeon Island reef and extensive feeding scars on the coral.

 Crown of Thorn starfish feeding on the corals at Pigeon Island

If the population density of Crown of Thorn is spread over more than 20-30 per hectare it is considered an outbreak . The present density observed on a casual dive was about double that density, he said. Therefore the true extent of the infestation is expected to be much higher as a greater part of the population may not be visible on a casual observation.

The Crown of Thorn has a mysterious life cycle. The starfish releases eggs and sperm into the water and when the eggs are fertilized naturally, they develop into a microscopic larvae stage that spends two to four weeks drifting as plankton in ocean currents. The juveniles settle on the reef . They live among rocks and rubble on the reef and are almost invisible until they are about six months old.

Arjan Rajasuriya of NARA too has observed the increase of Crown of Thorn starfish on a nearby coral reef in Dutch Bay in Trincomalee during a dive about two weeks ago. Mr. Rajasuriya recalling an outbreak of COT in the mid 70s said it had damaged many of the coral reefs in the East coast. He said a large number of snorkeling volunteers were employed to pick the COTs and bury them in the sand.

Mr. Rajasuriya fears that changing environmental conditions in the reef  could result in another outbreak. The floods in the East last year too may have contributed to an increased population of the star fish, the coral expert points out. The runoff water that ended in the sea that brings with it large amount of sediments and enriches the sea water with nutrients could have assisted the Crown of Thorn larvae to survive by producing enough food.

Global Warming too could have provided conditions for larvae to survive. Mr. Rajasuriya said that a single COT can lay more than two million eggs, so given the right conditions they can survive and an outbreak of Thorn of Crown can be as devastating as an outbreak of a swarm of Locust. Mr. Rajasuriya stressed the importance of monitoring the Crown of Thorn populations .

Two of the most widely tested and successful ways of controlling an outbreak of the Crown of Thorn Starfish are the physical removal of each and every star fish or killing them by injecting sodium bisulfate (dry acid) solution, he said.

DWC needs a dedicated Marine Unit
Pigeon Island has been declared a Marine National Park together with Hikkaduwa and Kalpitiya’s Bar Reef. The management of these marine national parks comes under the purview of the Department of Wildlife Conservation. But the department does not have a proper marine unit which has been highlighted by the Sunday Times.

An outbreak of Crown of Thorn starfish doesn’t happen overnight and a well equipped marine unit would have been able to detect such a situation. But the department is trying to manage the Marine National Parks similarly to the way they administer the terrestrial national parks such as Yala, the Sunday Times learns. Even officers who have been trained in diving have been transferred to land based national parks.

Source:http://www.sundaytimes.lk/120610/News/nws_47.html

Ocean fish populations dropping to alarmingly low levels

If over-fishing continues, commercial marine species could go the way of Lanka’s legendary pearl fisheries, which died out completely, warns environmentalist.

Malaka Rodrigo reports

Over-fishing is reducing fish populations to dangerously low levels in the Indian Ocean and seas around the world, warned fisheries experts. Dr. Rekha Maldeniya of the National Aquatic Resources Research and Development Agency (NARA) delivered the keynote speech at a seminar on Marine Biodiversity, on May 22, which was designated the International Day on Biological Diversity. Most of the common commercial fish stocks, including fish like the hurulla (herring), are depleted by over-exploitation, said Dr. Maldeniya, adding that sea cucumber, chank, lobster and shrimp are high on the list of threatened species. The expert quoted findings in the Fisheries Resources Survey, conducted over a four-year period (2006-2010). Coastal fish are the most in danger, but many offshore fish stocks, including tuna and shark, are over-fished, the expert said. Over-fishing led to the demise of the pearl oyster stocks, in Mannar, Dr. Maldeniya reminded the audience. Sri Lanka was once famous for its pearls, but that industry has died out completely, and the same fate awaits other fish species unless precaution is taken, she said. Management decisions are being delayed by a lack of sufficient data for a good understanding of the country’s coastal and marine ecosystems. “There is a lot of ongoing research on land-based ecosystems, but not enough research on marine ecosystems. Marine biodiversity research is expensive, and we do not have enough trained people to do the research. Even the little research output we have, such as the Environmental Impact Assessments, is under-utilised. While our main concern is commercially valuable fish species, other marine creatures are also under great pressure.” Weak enforcement of laws and regulations has also contributed to the decline in coastal fish stocks. Dynamiting and the continued use of banned types of fishing nets must end if fish stocks are to be maintained. Some countries use large nets such as the purse seine to catch tons of fish. Such action depletes stocks very quickly. Taking management action, the expert said, is not easy, as many fish stocks overlap ocean areas belonging to different countries. Some pelagic fish, like tuna, are migratory, so protection by one country alone does not ensure a species’ survival. All marine habitats are interconnected. For example, certain marine fish come to estuaries to breed, and if the estuaries are not protected, the species is threatened. Habitat loss, degradation and fragmentation, destructive fishing methods, pollution, the spread of invasive alien species – all are serious threats to marine life. Sri Lanka exports 20,000 metric tons of fish a year. A total of 650,000 people are employed in the fisheries industry, including 150,000 fishermen, 100,000 in fishing-related services, and 400,000 in the fish trade. Up to 2.4 million persons are sustained by fish consumption. Fish species contribute to 70 per cent of the country’s animal protein consumption. How much life is there in the sea? The marine biodiversity found around Sri Lanka ranges from microscopic algae to the giant Blue whale. During a 10-year period, from 2000 to 2010, scientists around the world collaborated in an unprecedented effort to determine how much life there is in the sea. The Census of Marine Life, carried out under the Convention of Biodiversity, involved 2,700 scientists from more than 80 countries. They studied surface seawater and probed the deepest, darkest depths of the ocean, sailed tropical seas and explored ice-strewn oceans in the Arctic and the Antarctic. By the time the census was concluded, a total of 1,200 new species had been added to the known roster of life in the sea. Scientists are still working their way through another 5,000 specimens to determine whether they are new discoveries. The number of known marine species is estimated at around 250,000. In its final report, the census team suggested the number could be at least a million, while others believe the figure could be double that. Source:http://www.sundaytimes.lk/120527/News/nws_24.html