Diel Vertical Distribution Patterns of Pelagic Fish Larvae in Yilan Bay, Taiwan

Abstract

To study the diel migration distribution of larval fish in an area adjacent to the Kuroshio Current, samples were collected from six depths by using a Motoda horizontal net at a fixed station in Yilan Bay on July 30 and 31, 2007. A total of 591 larval fish were collected and assigned to at least 34 families and 57 species. The first five dominant species were Benthosama pterotum (40.95%), Diaphus B type (12.18%), Callionymidae spp. (8.46%), Gobiidae spp. (6.60%), and Apogonidae spp. (4.0%). The density of larval fish varied across time. The maximum larval density was 1220.34 individuals/1000 m(3) at 19:00, and the minimum larval density was 81.84 ind./1000 m(3) at 14:00. The vertical distribution of species accounting for more than 10% of all fish caught was determined by the diurnal and nocturnal migration of the dominant species B. pterotum, which migrated from a depth of 50 m at night to 200 m in the afternoon. The distribution models for other species (e.g., Diaphus B type) were also analyzed in this study.