Temporal and Spatial Occurrence of Mesopelagic Fish Larvae during Epipelagic Drift Associated with Hydrographic Features in the Gaoping Coastal Waters off Southwestern Taiwan

摘要

This study analyzed the spatiotemporal occurrences of mesopelagic fish larvae in relation to environmental forcing in the Gaoping coastal waters off southwestern Taiwan during August 22–23, 2014 (summer), December 5–6, 2014 (winter), and April 28–29, 2015 (spring). Forty taxa or morphotypes of mesopelagic fish larvae were identified. Skinnycheek Lanternfish Benthosema pterotum (19.1%), Bristlemouth Cyclothone alba (11.6%), Spinycheek Lanternfish B. fibulatum (10.8%), Benthosema spp. (9.4%), and Neoscopelus spp. (9.2%) were the five predominant taxa. Maximum abundance of these taxa generally occurred during the cold period (winter and spring). Although the temporal difference in the abundance of mesopelagic fish larvae was not significant, the assemblage of mesopelagic fish larvae was more diverse in winter than in other seasons. Cluster and distance-based linear model analysis suggested a distinctly structured assemblage of mesopelagic fish larvae. The intrusion of the Kuroshio Branch Current played an important role in the transport of mesopelagic fish larvae. The distribution of mesopelagic fish larvae was closely related to the hydrographic features, with surface temperature and mixed-layer depth being the major factors affecting the occurrence of mesopelagic fish larvae. Also, the vertical mixing of the water column in winter induced the vertical distribution of natural food favorable for mesopelagic fish larvae. Received December 6, 2016; accepted February 5, 2017