To clarify the spatiotemporal distribution of the winter and spring larval fish assemblage in the coastal waters off Kaohsiung and Pingtung, Taiwan, larval fishes were collected during four research cruises by conducting 35 tows of the larval net in coastal waters off Zuoying, Linyuan, Linban and Fangliao in January and March 2009 and in coastal waters off Linyuan adjacent to the Kaoping River estuary in January and March 2010. Water temperature, salinity and dissolved oxygen were measured during the sampling of the fish larvae. Seawater samples were also collected for analyzing concentrations of nutrient salts. In 2009, a total of 2,023 fish larvae, representing 38 families and 74 species, were collected. The fish larvae assemblage exhibited seasonal variation in both abundance and species composition. The abundance (460 ind./1000m3) and the number of species (34 families and 66 species) of the fish larvae collected in March were higher than those (28 ind./1000m3, 14 families and 27 species) collected in January. Fish larvae also exhibited spatial variation in species composition. In January, the most dominant families of fish larvae were: Myctophidae off Linyuan, Sparidae off Linban and Nomeidae off Fangliao. In March, in the northward coastal waters off Linyuan Scombridae was the most dominant family, and in the southward coastal waters off Linyuan, Clupeidae and Sillaginidae were the dominant families. No significant differences existed in the abundance of fish larvae among the sampling areas, but the abundance of fish larvae in the sampling sites off Linyuan and Linban tended to be strongly influenced by tide. In 2010, a total of 1,959 fish larvae, representing 39 families and 59 species, were collected. These fish larvae showed diurnal and seasonal variations in abundance and in species composition. The abundance (767 ind./1000m3) and the number of species (39 families and 55 species) of the fish larvae in March were higher compared with those (26 ind./1000m3, 16 families and 25 species) in January. Moreover, the abundance of fish larvae in the nighttime was higher than that in the daytime. In March, the most dominant family in the daytime was Serranidae, whereas the most dominant family in the nighttime was Myctophidae, indicating the diurnal migration of Myctophidae these larvae. Cluster analysis indicated that the abundance and species composition of the fish larvae differed between January and March in 2009. The difference in species composition among the four sampling areas was only found significant for the fish larvae collected in the coastal waters off Fangliao in winter, and the most influenced families were Nomeidae and Myctophidae. In 2010, seasonal variations were found in the abundance and species composition of the fish larvae, and the abundance of the fish larvae showed the difference between nearshore and inshore sampling sites in the nighttime in winter. In spring, the fish larvae were all inshore fishes, but the species composition had annual variation. The temperature and salinity data obtained in the sampling sites conformed to the surface seawater of South China Sea, indicating that the occurrence of the dominant family Scombridae may be related to the seawater of South China Sea.

This thesis is focused on the fish spatial distribution and its changes mainly during the diel cycle. In the first part, I described the fish spatial distribution in the tropical lake ecosystem of Lake Turkana. The second part deals with the fish spatial distribution in a temperate reservoir on the different spatial scales from in/offshore habitats over the fine-scale to the level of individuals. The linkage of fish distribution patterns with selected environmental variables was also evaluated.

Blastodinium, a genus of the phytoplanktonic dinoflagellates, was found to be inhabiting the gut region of the copepod species Labidocera. Copepods are ubiquitous in aquatic environments, being the most numerous multicellular organisms on planet earth. Being primary consumers, they play important ecological roles, passing energy from one trophic level to the next. As zooplankton, estuarine copepods contribute substantially to carbon cycling as they undergo diurnal migration to avoid daylight UV-B damage and surface water predation. Blastodinium are presumed to infect copepods via ingestion of zoospores by juvenile hosts, who function as microhabitats for acquiring nutrients in non-photosynthetic species or in nutrient-limited environments. Blastodinium may hinder reproduction of copepod hosts, thereby influencing local copepod populations and, by extension, food webs up to humanity. Copepod populations may also help contain disease spread, such as malaria and Dengue fever, through their consumption of mosquito larvae in standing water. Further evaluation of copepods for Blastodinium may help shed light on the limited knowledge of this species and the nature of its relationship with copepods, as well as its effects on copepod populations and the higher order consequences of its parasitism.