Assessing Summertime Primary Production Required in Changed Marine Environments in Upwelling Ecosystems Around the Taiwan Bank

Abstract

The Taiwan Bank (TB) is located in the southern Taiwan Strait, where the marine environments are affected by South China Sea Warm Current and Kuroshio Branch Current in summer. The bottom water flows upward along the edge of the continental shelf, forming an upwelling region that is an essential high-productivity fishing ground. Using trophic dynamic theory, fishery resources can be converted into primary production required (PPR) by primary production, which indicates the environmental tolerance of marine ecosystems. This study calculated the PPR of benthic and pelagic species, sea surface temperature (SST), upwelling size, and net primary production (NPP) to analyze fishery resource structure and the spatial distribution of PPR in upwelling, non-upwelling, and thermal front (frontal) areas of the TB in summer. Pelagic species, predominated by those in the Scombridae, Carangidae families and Trachurus japonicus, accounted for 77% of PPR (67% of the total catch). The benthic species were dominated by Mene maculata and members of the Loliginidae family. The upwelling intensity was the strongest in June and weakest in August. Generalized additive models revealed that the benthic species PPR in frontal habitats had the highest deviance explained (28.5%). Moreover, frontal habitats were influenced by NPP, which was also the main factor affecting the PPR of benthic species in all three habitats. Pelagic species were affected by high NPP, as well as low SST and negative values of the multivariate El Niño–Southern Oscillation (ENSO) index in upwelling habitats (16.9%) and non-upwelling habitats (11.5%). The composition of pelagic species varied by habitat; this variation can be ascribed to impacts from the ENSO. No significant differences were noted in benthic species composition. Overall, pelagic species resources are susceptible to climate change, whereas benthic species are mostly insensitive to climatic factors and are more affected by NPP.

Distribution and Catch Rate Characteristics of Narrow-Barred Spanish Mackerel (Scomberomorus commerson) in Relation to Oceanographic Factors in the Waters Around Taiwan

“…During autumn, high CRs were distributed widely across the southwestern TS, including in the waters along the southwestern coast of Taiwan and between the Penghu Islands and the Taiwan Bank, and concentrated gradually in winter. Previous studies on upwelling in the TS have reported that upwelling is a yearround phenomenon, with the degree of upwelling varying in the water around the Penghu Islands and Taiwan Bank (Lan et al, 2009;Hong et al, 2011;Hsiao et al, 2021). Fronts and mesoscale eddies are formed in the Taiwan Bank through the interaction of different water masses and monsoons, which all influence larval species due to the dispersion and convergence of nutrients (Zhang et al, 2014;Hsiao et al, 2021).…”

“…Previous studies on upwelling in the TS have reported that upwelling is a yearround phenomenon, with the degree of upwelling varying in the water around the Penghu Islands and Taiwan Bank (Lan et al, 2009;Hong et al, 2011;Hsiao et al, 2021). Fronts and mesoscale eddies are formed in the Taiwan Bank through the interaction of different water masses and monsoons, which all influence larval species due to the dispersion and convergence of nutrients (Zhang et al, 2014;Hsiao et al, 2021). Hsiao et al (2021) revealed that the fishery resource structures in the frontal habitat of the Taiwan Bank are supported by both warm-and cold-water species, including S. commerson.…”

“…Fronts and mesoscale eddies are formed in the Taiwan Bank through the interaction of different water masses and monsoons, which all influence larval species due to the dispersion and convergence of nutrients (Zhang et al, 2014;Hsiao et al, 2021). Hsiao et al (2021) revealed that the fishery resource structures in the frontal habitat of the Taiwan Bank are supported by both warm-and cold-water species, including S. commerson. Weng et al (2020) reported the presence of hydrated and postovulatory oocytes for S. commerson in the central TS, implying that this area could be a spawning ground for this species.…”

“…Biogeographically, the Taiwan Strait (TS) and waters off eastern Taiwan are migration routes for numerous pelagic fish species; therefore, their ecosystem dynamics and biogeochemical and physical processes vary substantially in space and time (Liao et al, 2018;Ju et al, 2020;Lin et al, 2020). The WT constitute excellent spawning, feeding, and overwintering habitats (Hsu et al, 2007;Madigan et al, 2016;Hsiao et al, 2021). Overall, these unique features contribute to the abundant and multiple living fishery resources in the coastal waters off Taiwan, rendering these waters a valuable fishing ground (Wang et al, 2013;Lan et al, 2014).…”

Effect of the El Niño–Southern Oscillation (ENSO) Cycle on the Catches and Habitat Patterns of Three Swimming Crabs in the Taiwan Strait

“…Climate-induced habitat suitability changes may strongly influence fisheries (Kuczynski et al, 2018). For example, in the southern TS, pelagic species resources are susceptible to climate change, whereas benthic species are mainly insensitive to climatic factors (Hsiao et al, 2021). This variability may explain changes in CRs in suitable and optimal habitat areas caused by ENSO events in the TS.…”