Extensive fieldwork on Sri Lankan seagrasses. Dugongs highly valued for meat in Sri Lanka.
August 22, 2016
LK6 Project Update: Jan thru June 2016
The reporting period coincided with the beginning of the diving season and completion of securing necessary equipment and security clearances. The team had to engage in setting up and streamlining the field procedures for surveys and construction of methods for transport and mounting of equipment on boats.
Based on the CMS Dugong MoU bycatch questionnaire data and the significant data sets collected by ORCA through field community surveys and the analysis of aerial images and past data, a base plan was formulated for identification of priority areas for conducting field surveys. The area south of Mannar was focused on initially as more facilities were available within this area and sea conditions were also better.
A botanist was engaged to train the team in identification and seagrass surveys as the main team experience had been primarily in coral reef surveys; the botanist will continue to support the team in the assessment of data.
The specimens of seagrasses, collected by ORCA during the field surveys under LK6, were donated to the national plant repository at the Herbarium in Peradeniya. More than 54 herbarium specimens of seagrass and algae were deposited. Another 40+ specimens are under preparation for depositing at the national herbarium representing various surveyed locations.
ORCA found that the overall predicted dugong area extends about 1500 km2 south of Mannar and 2500 km2 north of Mannar Island. Most of these areas have not been surveyed and their research would require significant sampling, which was found beyond the financial capacity of LK6. The team designed a survey plan on high probability areas within the region based on available sighting/capture records and possible seagrass areas.
24 field surveys were carried out between Kudiramale and Illuppaikadavi, North of Mannar island in the period January – April 2016. The surveys were carried out using also a track side scan sonar to identify probable areas of seagrass from sandy or rocky substrates and a small grab hook was used to carry out spot check samples for substrates. When a good site was located, snorkel or scuba survey dives were carried out to collect data.
During the survey nine seagrass species were found in various depths from 0.5 m to 14 m: Cymodocea serrulata (R.Br.) Asch. & Magnus, Cymodocea rotundata Asch. &Schweinf, Syringodium isoetifolium (Asch.) Dandy, Halophila ovalis (R.Br.) Hook.f, Halophila decipiens Ostenf,
Halophila stipulacea (Forssk.) – a new record to the Sri Lankan floral list,
Asch, Halodule uninervis (Forssk.) Boiss, Thalassia hemprichii (Ehrenb. ex Solms) Asch and Enhalus acoroides (L.f.) Royle. In one of the studied areas, significant populations of the algae Caulerpa taxifolia, identified as an invasive species on seagrass environments in other parts of the world, were found.
ORCA also conducted 12 days of community surveys from Kalpitiya, Serakkuliya. Vanthawilluwa, Gangewadiya, Eluwankulam, Mannar, Vedithalathivu, Illuppankadavi, Veravil to Devils point.
Based on the available data, ORCA identified that the core area of dugongs in the Gulf of Mannar might be the area of the West Cheval Banks and Periya-paar located North of Battalangundu Island and 15-20 km, West of the coast at Mollikulam. A high incidence of dugong takes are also recorded from the outer area of the Vankale reef.
Based on the information available on average one dugong is captured and sold for meat per month within the area. There are significant number of young animals being caught or reported, on the basis of which ORCA concluded that there might be still a good breeding population surviving.
The trade of dugong meat is very lucrative. The high demand for dugong meat make it easy to sell as well as fetching high prices.
A large individual can fetch up-to Rs.600,000 (note by PCT: approximately USD 4,108) at the point of selling it off on the beach.
Apparently most turtles that drown in the nets are thrown away and not butchered as the risk for fishermen getting caught does not make it worth their while (concluded by the numbers of dead turtle carcasses found adrift at sea or washed up on beaches). But dugongs when caught are almost always brought ashore for sale.
The greatest threat to dugongs come from the gill net fishery for rays; as this is one of the primary fisheries of the area contributing significantly to the local economy, it would be difficult to ban the use of it without a significant effort to promote an alternative and less destructive fishery practice. Such efforts in promoting alternative livelihood must focus on the fishermen in the area of Battalangundu Island, and North along the coast from Mollikulam to Mannar Island with prominence given to South Bar area. The illegal poaching in the area by large Indian trawlers are of serious concern both for seagrass beds as well as the dugongs.