Temporal succession and spatial segregation of clupeoid larvae in the coastal waters off the Tanshui River Estuary, northern Taiwan

In the coastal waters off the Tanshui River Estuary in northern Taiwan, eight species of clupeoid larvae were observed. They exhibited a distinct temporal succession in association with seasonal temperature changing. The time of peak abundance of Etrumeus teres was in January, Engraulis japonicus in late April, Sardinella spp. in mid-May, Dussumieria elopsoides in early June, Thryssa dussumieri in late June, Stolephorus insularis in mid-September, Encrasicholina heteroloba in early October and E. punctifer in mid-November. The time intervals of the temporal succession of the fishes were approximately 15 to 25 d in the spring/summer and 25 to 35 d in the autumn/winter fishing seasons. Also, they showed spatial segregation by distributing in areas with different water depths: Sardinella spp. at a water depth of 10 to 20 m, T. dussumieri at less than 10 m, E. heteroloba at 20 to 50 m and E. punctifer at 10 to 40 m. The larvae of these sympatric clupeoid species segregated their nursing periods and areas apparently to reduce competition for habitat and thus to maximize the utilization of resources.