A total of 155 puffers caught from two of Thailand's seas, the Gulf of Siam and 
the Andaman seas, during April to July 2010 were included in this study. Among 
125 puffers from the Gulf of Siam, 18 were Lagocephalus lunaris and 107 were L. 
spadiceus which were the same two species found previously in 2000-2001. Thirty 
puffers were collected from the Andaman seas, 28 Tetraodon nigroviridis and two 
juvenile Arothron reticularis; the two new species totally replaced the nine 
species found previously in 1992-1993. Conventional mouse bioassay was used to 
determine the toxicity in all fish tissue extracts, i.e., liver, reproductive 
tissue, digestive tissue and muscle. One of each of the species L. lunaris and 
L. spadiceus (5.56 and 0.93%, respectively) were toxic. All 28 T. nigroviridis 
and 2 A. reticularis (100%) from the Andaman seas were toxic. The toxicity 
scores in T. nigroviridis tissues were much higher than in the respective 
tissues of the other three fish species. Liquid chromatography/tandem mass 
spectrometry (LC-MS/MS) revealed that the main toxic principle was tetrodotoxin 
(TTX). This study is the first to report TTX in L. spadiceus. Our findings 
raised a concern for people, not only Thais but also inhabitants of other 
countries situated on the Andaman coast; consuming puffers of the Andaman seas 
is risky due to potential TTX intoxication.