Turtle Project - Ko Man Nai Island Traditional Geocache

Concerned about the rapid decline of sea turtle populations in Thailand, Her Majesty the Queen Sirikit initiated the “Queen’s Project on Sea Turtle Conservation” in 1979. On the 11th of August of that year, Her Majesty donated her island property named Koh Mannai to the Department of Fisheries, for the establishment of the project. 

Located off the coast of Rayong Province in the northern part of the Gulf of Thailand, the island has a total area of about 22 hectares. 

In 1985, the project was transformed to become the “Sea Turtle Conservation Station” under the Department of Fisheries. Since 2003, the station has been operated by Department of Marine Costal and Resources (DMCR), of the Ministry of Natural Resources and Environment. 

The present project has three main objectives:



(1) To increase the number of sea turtles in the wild by protecting eggs in a hatchery. The hatchlings are reared for a certain period before tagging and release into the ocean to replenish natural stocks.

(2) To keep some adult turtles for breeding stocks, as well as to rescue and treat stranded or injured turtles.

(3) To promote and disseminate information and technical knowledge about sea turtle conservation and breeding. 

The centre piece of the Mannai Sea Turtle Conservation Station is the “breeding lagoon”, covering an area of about 5 hectares. The lagoon was designed by the Department of Fisheries, and is based on a water flow concept. Work to build the permeable concrete wall began in 1986 and was completed in 1988. The beach enclosed by the lagoon is used for nesting.

In the past Mannai Island was uninhabited, so the main initial challenge was to install public utilities. There was no electricity or water supply at that time. The pioneers had to adapt themselves and they developed the project from the ground. Nowadays, the problem is transportation between the mainland and the island especially during monsoon season (May-October). Due to strong winds and very rough sea waves, it is difficult to manage routine work.

Currently, 16 full-time staff work at the station, including 8 sea turtle caretakers and 6 technical staff members for equipment maintenance. A fisheries officer and veterinarian visit the island about 5 times a month. 

Breeding and captive rearing

Over the years, the Hawksbill turtle (Eretmochelys imbricata) has been bred in captivity and the hatchlings raised with some success. Green turtles are also raised from hatchling stage for release, and some are kept at the station for education purposes.

The station has adopted two techniques for breeding and rearing sea turtles in captivity – the first by acquiring hatchlings through natural breeding. This has been done since the inception of the project. Periodically DMCR staff visit Khram Island in nearby Chonburi province, which is the largest nesting site for turtles in Thailand. Nests found in good condition are left in that state. Otherwise, if a nest is not in a safe condition – for example, if it is threatened by inundation or predation – staff relocate the eggs to a safer place. 

The nests are monitored frequently until hatching occurs, at which time some of the hatchlings (less than 50%) are taken back to raise at the station. 

In the first stage – up to one year – baby turtles are reared in nursery tanks. The operation systems and structure of the nursery and rearing tanks were adapted from other aquatic ponds. However, filter systems are not necessary: all tanks are cleaned and the water is completely changed every day.

Some of these juveniles are released to the sea after they are at least one year old. The rest continue to be reared in the juvenile tanks to serve as future breeding stock. 

One of the problems that the station has had to address is mortality during the post-hatching stage caused by a disease known as Steatitis or yellow fat disease. It is a disorder characterised by marked inflammation of fat tissue and the deposition of wax pigment in between layers of fat tissue. It is caused by an excess of unsaturated fatty acids in the food, especially in frozen fish that is commonly used to feed baby turtles, and a deficiency of vitamin E. Adding vitamin E with the meal once a week can reduce the rate of mortality by this disease. 

The second technique, captive breeding, was initiated in 2001. This technique is still in the experimental stage. At present, 41 adult turtles raised from hatchling stage are being kept in the breeding lagoon as parental breeding stock. Their ages range from 10 to 24 years old, with an average age of 16.5 years.

Some of the adult turtles that have been raised in the lagoon are selected as parental breeding stock, and are moved to a confined place inside the lagoon for breeding. 

So far this technique has not proven very successful. Only one or two nests have been found each year on the inner beach behind the lagoon. Each nest contains about 100 eggs, but the ratio of successful hatching is relatively low, only 5-10%. It is thought that this failure might be caused by too young breeding animals, since the suitable age of breeding stock should be around 20-30 years old. 



         Statistics on captive breeding, rearing and release of sea turtles 

* Less than 50% of these hatchlings are brought to the station for captive rearing. Normally in their natural state, the percentage of unhatched eggs is about 20-30 %. Undeveloped egg percentage is about 10%. 

** The mortality rate of hatchlings during rearing is about 30%. All released turtles, aged more than 1 year, have a microchip embedded before release. Occasionally, the station receives reports of tagged turtles being found. 

Awareness activities



The sea turtle conservation project has now been in operation for almost 30 years. It has conducted many activities in order to conserve sea turtles including awareness-raising, education activities, and sharing of technical knowledge. On the island, there is an exhibition building to display the information on the centre, its activities, and other work related to sea turtles and other marine animals.

Additionally, workshops (especially in veterinary field) are conducted regularly in collaboration with some universities. There is also a hospital for marine animals at the centre, where sea turtles recovered as by-catch are treated and released. About 12 turtles are treated each year. 

The station organises a “Sea Turtle Release” activity every year in mid-April during Songkran (Thai New Year) festival. This event aims to promote sea turtle conservation and to increase awareness by encouraging fishermen and local community to participate.

From November 2006 to April 2007, the number of registered and un-registered visitors to the centre was 2,520 and 8,000, respectively, for a total of approximately 10,520. 

The station’s location – being on an island – limits to some extent the effectiveness of programmes aimed at widely promoting public education, awareness and information. Only a certain number of people can visit the station at a time and, as mentioned above, the weather can be problematic.

While some collaboration exists with other organisations in relation to activities at the centre, there is always room for improvement. 

For example, domestically there is information sharing and research with other research centres under the Department of Marine and Coastal Resources; the Royal Thai Navy; and the Department of Fisheries. Technical knowledge and research results are also disseminated to the Southeast Asia Fisheries Development Center (SEAFDEC). Internationally, the station collaborates with the satellite tracking project of SEAFDEC and cooperates with so-called “SEASTAR2000” project for regional research on sea turtles. 

Plans for the future

The centre plans to continue all these activities in order to conserve sea turtles and other marine animals; however future efforts will focus on the quality of released turtles rather than the quantity. Only a certain number of turtles (about 100-200) will be raised for release to ensure that all turtles are healthy and able to survive in the wild. Some turtles will be transferred to an area in the lagoon prior to release to expose them to natural conditions.

Presently, the station is conducting studies on sea turtle semen collection and evaluation. The research is focusing on the quality, fertility, and the effectiveness of the electro-ejaculator. This is expected to lead to more successful artificial insemination. Further efforts will concentrate on finding the best way to preserve sea turtle semen.

Taking a broader perspective, there is an on-going project to develop a national master plan for sea turtle conservation and management, based on available scientific data. This effort is being pursued in collaboration with all relevant institutes in Thailand. This represents a further step in efforts to protect and increase number of sea turtle populations in Thailand.

For more information about the work of the Koh Mannai "Sea Turtle Conservation Station", please contact: mannai@loxinfo.co.th.