Marine Snake Diversity in the Mouth of the Muar River, Malaysia

Abstract

Prior to entering the Straits of Malacca the Muar River meanders nearly at sea level for about 20 kilometers. Much of this portion of the river is influenced by semi-diurnal tides that occur in the Straits. In the 1970s and 1980s several stationary stake nets (kelongs) located adjacent to the town of Muar were operated by local fisherman. Besides the sought after catch of shrimp, squid, and fish, the harvest from these nets often included a by-catch of marine snakes. Collections over a period of eight months revealed that eight resident species were present in the mouth of the Muar River and that the beaked sea snake, Enhydrina schistosa, strongly dominated the assemblage of snakes. Surprisingly the relative abundance of species differed between several of the nets despite the fact that they were all located in a relatively small area and in one place located within just ~10 m of each other. Some small differences in species diversity between tidal periods were also detected at one of the nets. A review of published marine snake surveys conducted in Southeast Asian and Australian seas revealed that only four provided data on relative abundance of marine snake species in a defined small area on a scale of < 100 km2 . Although the Muar survey demonstrated the lowest species diversity values of the published studies, it also covered the smallest spatial scale surveyed and yet it still revealed differences within the survey area. This work emphasizes the fact that marine snake species diversity needs to be understood on a fine spatial scale before surveys done by trawling, which cover thousands of km2, can be interpreted in ecological terms.