Southern Taiwan’s Kenting National Park is a popular retreating place for many domestic and international tourists, with increasing tourist numbers potentially over-burdening the coastal ecosystems. To better understand human impacts, a long-term ecological research program was initiated in 2001 to track water quality at 14 coral reef-abutting sites throughout the park since then. Extracting the data from this 20-year survey, we found that increasing in the nutrient levels during the summer rainy season, together with the drops in salinity led by freshwater inputs (land- & rainfall-derived), was the main impact to coral reef ecosystem of Kenting. Cluster analysis further confirmed the nutrient influx was mainly attributed to the local discharge outlets with dense of villages and hotels at upstream. Therefore, more efforts are needed to input to control tourist number, treat waste water discharge and strengthen land protection facilities.

To understand the spatial species diversity of demersal fish assemblages in Taijiang National Park (TJNP) of Taiwan, fishes from 44 demersal trawl hauls and environmental data were collected in the nearshore and offshore areas of TJNP from April 2016 to May 2019. In total, fishes of 47 families, 84 genera, and 113 species were recorded. The nearshore and offshore demersal fish assemblages in TJNP exhibited significant variability in species composition assessed via beta diversity. Using distance-based redundancy analysis, we demonstrated that bottom depth and substrate type were significant explanatory variables of spatial species diversity and identified three habitat types (I: shallow soft bottom; II: deeper soft bottom; III: deeper bottom with mixed sand and gravel substrates). The nearshore assemblage was characterized by type I, where Tarphops oligolepis (flounder), Trachinocephalus myops (snakefish), and Liachirus melanospilos (carpet sole) dominated in terms of abundance. The offshore assemblage was characterized by either type II or type III because differences in substrate types among sampling sites were noticeable. At the offshore sites characterized by a deeper soft bottom (type II), Johnius distinctus (croaker), Cynoglossus kopsii (shortheaded tonguesole), and Coelorinchus formosanus (Formosa grenadier) predominated. In contrast, the westernmost sampling site, characterized by type III habitat, exhibited relatively high Shannon indices, and Scorpaena miostoma (scorpionfish), Urolophus aurantiacus (sepia stingray), and Parabothus taiwanensis (lefteye flounder) predominated. Our results provide the first baseline information on the environmental characteristics and spatial species diversity of demersal fish assemblages in TJNP and have implications for biodiversity conservation in existing spatial management areas.

We investigated changes in the assemblages of summer mesopelagic fish larvae between El Niño events and regular years in 2014–2018 and evaluated their relationships with the hydrographic conditions of the Gaoping waters off southwestern Taiwan. Seventy-five taxa or morphotypes were identified, with five types of Benthosema pterotum (31.2%), Diaphus slender type (19.9%), Cyclothone alba (7.2%), Diaphus stubby type (5.9%), and Vinciguerria nimbaria (4.4%) being most common during the study period. The hydrographic conditions of the Gaoping waters were likely influenced by large-scale climate change via oceanic physical processes. Apparently higher seawater temperature, mixed layer depth, and lower salinity in the upper 100 m were observed at the end of the strong El Niño events (summer 2016). In addition, the certain dominant taxa exhibited contrasting patterns between El Niño events and regular years. In this study, although the abundance and composition of mesopelagic fish larvae assemblage were not influenced directly by changes in large-scale climatic conditions, the occurrence of mesopelagic fish larvae was related to seawater temperature, salinity, and chlorophyll a concentration. We speculated that despite the abundant food availability and the more mesopelagic fish larvae onto the Gaoping waters transported by the increased inflow of the South China Sea Surface Current during El Niño events, the higher temperature and lower salinity at the inshore upper waters might be unsuitable for mesopelagic fish larvae, possibly resulting in low egg and larval survival.

The fluctuations in both time and space of larval fish assemblages in relation to hydrographic characteristics in the waters surrounding Taiwan Bank were studied in October 2021 (autumn) and March 2022 (spring). Throughout the study period, we identified a total of 149 taxa of fish larvae, encompassing 96 genera and 71 families. Engraulis japonicus, Diaphus slender type, unidentified Gobiidae, Apogon sp., unidentified Clupeidae, and Benthosema pterotum were the six dominant taxa and together constituted 47.39% of the total catch. There were no notable temporal variations observed in the abundance of fish larvae, but the species number of fish larvae was greater in spring than in autumn. Significant variations in species composition were observed between the different cruises, and the cluster analysis unveiled a distinct temporal structure of the assemblages of fish larvae. The dynamics of the prevailing currents induced by seasonal monsoons contribute significantly to the transportation of fish larvae. The distribution of fish larvae showed a good association with hydrographic characteristics, where seawater temperature and salinity emerged as the primary explanatory factors influencing the composition of larval fish assemblages in the waters surrounding Taiwan Bank. While the increased influx of nutrients from upwelling ensures abundant food availability, the hydrographic conditions may not be suitable for every fish larva.