GIANT CLAM NURSERY

Giant clams are one of the most ecologically important organisms in a coral reef, known as a keystone species. Like hard corals, Giant clams use symbiotic zooanthallae algae to produce a shell that adds to the reef structure. In addition to this, they clean nutrients from the water that could otherwise go towards the growth of macroalgae, smothering and killing corals. A single Giant clam can filter 100s of liters of water in a single day, and only where there are giant clams do we see high coral abundance and biodiversity.

Unfortunately, these slow growing clams are being harvested for food and decoration, a practice which is unsustainable and benefits only a few individuals. To increase awareness and help to repopulate Koh Tao’s reefs Save Koh Tao will be developing a long term nursery and release program in addition to releases conducted yearly by dive schools and the Thai Navy. Save Koh Tao received 100,00 baht budget from the local government to begin this project in January of 2009.

One of our ecodivers examining the giant clams in Ao Leuk.

In March 2009, Save Koh Tao received 1000 juvenile giant clams and we put them down in 10 cages in Ao Leuk on the islands east side. This project is part of a larger program to restore the populations of ecologically important giant clam species which have been depleted due to over extraction and human activities. The goal of the project is to allow the juvenile clams to mature in a predator free, but natural, environment and then transplanted out onto the reef when they become more mature.

It was anticipated that not all the clams would survive in any project dealing with juveniles due to several factors – predation, disturbance events, disease and natural attrition. Mortality rate was high in the beginning but levelled off once they had established themselves.

In 2010 we will receive more juvenile clams and hope to be able to improve on the survival rates of this important species.