Ichthyofauna on a Tropical Mudflat: Implications of Spatial and Temporal Variability in Assemblage Structure and Abundance

Often seen as nonvegetated unutilized wastelands, mudflats pose the least resistance to land claim for coastal development. Here, we studied the large Klang mudflat (Straits of Malacca) from September 2011 to September 2014 to determine the fish species that utilize it and the abiotic factors that influence species composition and abundance, to evaluate the ecological role of the mudflat in support of coastal fisheries. The spatial and temporal assemblage of fish species and their abundance was examined at two sites, during two monsoon seasons, and under the effect of period (wet/dry), moon phase (full/new moon), and diel cycle (day/night). Fish were sampled during ebb tide by a stationary large barrier net that enclosed a calculable area of sampling. A total of 119 species belonging to 46 families of mainly small-sized and juvenile fish made regular ingressions into the mudflat throughout the year. Fish abundance varied spatially and temporally, suggesting site preference and variability in juvenile recruitment. Higher fish abundance due to recruitment occurred during the northeast monsoon season (NEM), as compared to the southwest monsoon. Fish composition but not total fish abundance during the NEM differed between wet/dry periods and diel cycles. Ariidae and Sciaenidae were dominant families during the wet period, whereas Engraulidae dominated during the dry period. Predatory fish species (e.g., Lagocephalus lunaris, Otolithes ruber, and Hexanematichthys sagor) were recorded during the daytime, whereas planktivorous and detrivorous species (e.g., Ambassis gymnocephalus and Liza subviridis) were more abundant during the night.