PSU finds environmental changes the causes of mussel deaths in Trang

Faculty of Natural Resources, PSU has learned about the death of farmed mussels in Tambon South Kantang, Amphoe Kangtang, Trang Province where there are 89 mussel farmers. The Faculty studied the cause of the death which had begun since August 18, 2009 and found that the area had increased the number of farmed mussels 2-3 times.

Crowdedness resulted in bad water circulation leading to smaller quantity of nutrients available for each mussel and sudden environmental changes. These, in turn, caused stress and eventually weakness in the mussels. When they died and decayed, the water condition deteriorated and bred more parasites and microbes, causing even more rapid and massive deaths.

Part of the changes has resulted from the decrease of water salinity due to heavy rains in the watersheds. Mussels died most on heavy rainy days beginning from the rafts 3 kilometers before the village. More of those at the top of the sacks died than those at the bottom because the changes at that level were more drastic, i.e., the salinity level changed more quickly than that at a deeper level. There were no reports about the death of white sea bass, however, because they could live in water with ranges of salinity level and so not affected. The rain wash also incurred various colored sediments, becoming a problem to mussels which feed by filtering though they have mechanisms to manage suspended sediments.

The study team has made suggestions to mussel farmers as follows. Mussel farming relies on natural settings so farmers should consider the capability of the system in catering for it. This means the management of natural environment to make it sustainable, balanced and undisturbed so as not to incur any phenomenon that has never occurred before. In this case, the farmers will have to reduce the number and the size of the mussel rafts as well as not to make the mussel sacks too overcrowded in each raft.