Abstract

Spatio-temporal patterns of marine and brackish water fish assemblages gradated from the upstream of the anti-salt dam "Uthokawiphatprasid" dam to the Pak Panang Bay, southern of Thailand. The samples were collected between March 2006 to June 2007at six sampling sites (three sites each from above and below the dam). A total of 70 fish species belonging to 68 genera and 44 families were sampled. To analyze patterns of fish assemblages, an artificial neural network (ANN) in the form of a self-organizing map (SOM) was applied. The sample-combinations (sluice gate regime (opening or closing), sampling stations and months of sampling) were classified into four clusters related to the spatial location and sluice gate regimes. Six assemblage patterns were further explained by the probability of occurrences and ranges of salinity levels. The largest group was opportunistic marine fish (21 species) followed by true brackish water fish (17 species). Others comprised of steno- and eury-haline fish as well as the anadromy. The likely impacts of each guild due to the dam regulations and further studies for conserving these fish were also discussed.