Zoological Studies

Spatial Genetic Structure of the Surf Clam Paphia undulata in Thailand Waters

Patipon Donrung, Suriyan Tunkijjanukij, Padermsak Jarayabhand, and Supawadee Poompuang (2011) The surf clam Paphia undulata has supported an offshore fishery in Thailand since the 1970s. However, most fishing sites have experienced declines in production over the past 2 decades. Overexploitation and low levels of genetic variation of surf clam populations may be responsible for the low productivity of the species. Intersimple sequence repeat (ISSR) markers were used to assess the genetic diversity of surf clams sampled from 4 fishing areas in the Gulf of Thailand and 1 location in the Andaman Sea. In total, 300 ISSR loci were analyzed in 500 individuals. Three neighboring populations (SG, SS, and SP) in the upper Gulf of Thailand exhibited moderate genetic variation and similar Nei’s gene diversity (H_j) values of 0.12-0.14, while populations from the lower Gulf of Thailand (SR) and the Andaman Sea (ST) had relatively low genetic variability with respective H_j values of 0.053 and 0.047. Different analyses, including F_ST, AMOVA, phylogenetic networks, and an assignment test revealed high levels of population substructuring, implying that gene flow may occur between stocks in the upper Gulf of Thailand, whereas the SR and ST populations were more geographically isolated. The relatively low amount of genetic diversity of the SR and ST stocks may reduce their ability to survive in a changing environment. Reductions of fishing efforts, and initiation of restocking programs and aquaculture development of this species should be considered to maintain the sustainability of the surf clam fishery.