WINTER ABUNDANCE AND SPECIES COMPOSITION OF ANCHOVY LARVAE ASSOCIATED WITH HYDROLOGICAL CONDITIONS IN THE COASTAL WATERS OF TANSHUI, TAIWAN

Abstract

The present study investigated changes in the winter abundance and composition of anchovy larvae associated with hydrological conditions in the coastal waters of Tanshui, Taiwan. A survey during the period of 2008-2014 revealed that the abundance of larvae caught using fyke nets varied from 123.9 to 28,314 ind/1000 m^3, whereas the surface water temperature and salinity ranged from approximately 17°C to 18°C and 32.84 psu to 33.72 psu, respectively. Engraulis japonicus (Japanese anchovy), Encrasicholina punctifer (buccaneer anchovy), and E. heteroloba (shorthead anchovy) were the dominant species of anchovy larvae, accounting for 0.17%-93.56%. In the La Nina years 2008 and 2011, Japanese anchovy was dominant, with a relatively high abundance of approximately 128-25,432 ind/1000 m^3 when the current at 10-m depth moved southwestward. In the El Nino years 2010 and 2014, buccaneer anchovy and shorthead anchovy were the dominant species, with a relatively low abundance of approximately 0.21-8,334.38 ind/1000 m^3 when the current at 10 m depth moved northeastward. The change in the pattern of currents induced by El Nino-Southern Oscillation events may be crucial in determining the winter abundance and species composition of anchovy larvae in the coastal waters of Tanshui. Additionally, an elevated sea surface water temperature probably reduces the abundance of Japanese anchovy and increases that of buccaneer anchovy and shorthead anchovy in winter.