Larval Fish Assemblages and Hydrographic Characteristics in the Coastal Waters of Southwestern Taiwan during Non- and Post-typhoon Summers.

Hung-Yen Hsieh, Wen-Tseng Lo, Hsiao-Hao Chen, and Pei-Jie Meng (2016) Although research on the larval fish assemblages in the Taiwan Strait has progressively developed in the last two decades, it is difficult to study typhoons' impacts on larval fish assemblages due to (1) the occurrence and path of a cyclone cannot be predicted accurately and (2) the severe weather condition makes shipboard measurements extremely difficult. Larval fish and zooplankton were sampled and hydrographic variables and chlorophyll a were measured in the waters of southwestern Taiwan during September 2009 (non-typhoon) and September 2012 (post-typhoon Tembin). Data from these collections were used to elucidate the effects of hydrographic dynamics after the typhoon event on species assemblage and abundance. The results showed that after the typhoon Tembin, the surface temperature and salinity decreased slightly, but the values of the measured chemical and biological parameters were much greater than those derived from the non-typhoon period due to enriched nutrients from entrainment of river runoff of the Kaoping River. Meanwhile, the abundance of larval fish also increased significantly, but the species composition became less diverse. Multivariate statistical analyses revealed two distinct larval fish assemblages that were closely correlated to sampling cruise. The dominant taxa of larval fish changed from Encrasicholina heteroloba, Nuchequula nuchalis, unidentified Sparidae, Equulites rivulatus, and Cyclothone spp. during the non-typhoon period to Engraulis japonicus, unidentified Engraulidae, Sillago sihama, Pennahia argentata, and E. rivulatus during the post-typhoon period. Canonical correspondence analysis revealed that, in the waters of southwestern Taiwan, the horizontal distribution of larval fish in late summer may be explained by the food availability. The magnitude of the enhancement of measured variables changed with sampling periods, suggesting the study area was at an unsteady status after the passage of the typhoon Tembin. The coastal ecosystem became more productive after the typhoon event.