Comparison of Ichthyoplankton Assemblages with Hydrographic Condition across the Northern Margin of the Taiwan Strait as the Monsoon Interim

Abstract

Distribution of ichthyoplankton assemblages in the northern margin of the Taiwan Strait was investigated in concert with the properties of water masses. By diagrammatic analysis of the temperature and salinity distribution, the waters along a transect line from Matzu to Tamshui could be categorized as two typical waters of China coast (CCW) and the Kuroshio related (KrW). The water situated between the two typical members was frequently identified as frontal zone. The CCW was shown vertically stratified, but the KrW mixed well with uniform temperature and salinity profiles. Principal component analysis of station-specific ichthyoplankton composition also exhibited distinctive groups of Fukien coast, frontal and northern Taiwan, in accordance with the waters of CCW, frontal and KrW. Low density of fish eggs occurred during onset of northeastern (NE) monsoon, in contrast to that at the end of NE monsoon when fish eggs concentrated in the eastern part of Taiwan Strait. The water mass with higher density of fish larvae located in the vicinity of Fukien coast as onset of NE monsoon, and this shifts toward the eastern part of Strait when the monsoon came to an end. In total, 1177 fish larvae collected were classified into at least 41 species and 27 families. Species composition differs between those two monsoon interims. At the commencement of monsoon period, Bregmaceros nectbanus was found predominately along the Fukien coast and the frontal zone, and Encrasicholina heteroloba in northern Taiwan. At the end of monsoon, Scomber japonicus and Platycephalus indicus become overwhelmingly in the Fukien coast, Benthosema pterotum in northern Taiwan, and Engraulis japonicus in the frontal zone. On the western side of the Strait, a lens of higher fluorescence value was developed at the end of NE monsoon, but neither zooplankton nor fish aggregations found correspondingly.