Present status and long-term monitoring of reef fish assemblages in Patong bay, Phuket: Technical paper no. 4/2002

Surveys of fishes, applying visual census technique, at three reef sites in Patong Bay since 1991 have revealed a total record of 227 species representing 42 families, of which 176 species in 36 families were found in the present survey result. Fish abundances, in terms of both total number of species and total number of individuals per census area, were not statistically different among sites. The community level analysis (using multivariate statistical method), however, showed that fish assemblages were markedly different among reef sites. Such spatial differences of fish assemblage were strongly influenced by physical or morphological structures of the coral reef habitat at each site. Water quality also seems to be responsible for the spatial differences of fish assemblages, particularly at the reef site in the inner part of southern Patong. This site is considered to receive direct impact from sewage flowing out through Pakbang canal. Temporal structure of fish assemblages was also analyzed using the long-term monitoring data gathered since 1991. This revealed a consistency of assemblage structure at each reef site over a period of the last 10 years. Because the assemblage pattern of fishes at each site in the previous time was unknown, the following two speculations could be taken into consideration. First, if the present assemblage at certain reef site reflects the pattern that had been changed according to the influences of degraded environmental conditions, it seems likely that fish community in the area has not yet recovered or improved. Second, if the present assemblage pattern has been retained since the past, the present situation of environmental changes or degradation has not yet exceeded the capabilities of fish populations to either withstand or adapt to it. Nevertheless, further degradation of coastal environments might adversely affect either fishes or other coral reef resources. Immediate action is urgently needed to solve environmental degrading problems, particularly that concerning sewage discharge, before it is too late to secure the wealth of marine resources in Patong Bay.