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Abstract: The ecological conversion efficiencies in twelve species of fish in the Yellow Sea Ecosystem, i.e., anchovy (Engraulis japonicus), rednose anchovy (Thrissa kammalensis), chub mackerel (Scomber japonicus), halfbeak (Hyporhamphus sajori), gizzard shad (Konosirus punctatus), sand lance (Ammodytes personatus), red seabream (Pagrus major), black porgy (Acanthopagrus schlegeli), black rockfish (Sebastes schlegeli), finespot goby (Chaeturichthys stigmatias), tiger puffer (Takifugu rubripes), and fat greenling (Hexagrammos otakii), were estimated through experiments conducted either in situ or in a laboratory. The ecological conversion efficiencies were significantly different among these species. As indicated, the food conversion efficiencies and the energy conversion efficiencies varied from 12.9% to 42.1% and from 12.7% to 43.0%, respectively. Water temperature and ration level are the main factors influencing the ecological conversion efficiencies of marine fish. The higher conversion efficiency of a given species in a natural ecosystem is acquired only under the moderate environment conditions. A negative relationship between ecological conversion efficiency and trophic level among ten species was observed. Such a relationship indicates that the ecological efficiency in the upper trophic levels would increase after fishing down marine food web in the Yellow Sea ecosystem. [Copyright &y& Elsevier]

The Pacific decadal oscillation (PDO) has been identified as an important driver for fluctuation of fish populations on the eastern Pacific Ocean. However, the relationship between changes in fish population and climate oscillations on a decadal time scale in the Northwest Pacific is still unclear due to the lack of reliable long-term time series data. In the present study, a time series of Engraulis japonicus (Japanese anchovy) populations was reconstructed using the density of sedimentary fish scales in the Yellow Sea basin. E . japonicus populations and the PDO index showed similar patterns on a decadal time scale. Our results confirm that climate is a major driver of ecological changes on a decadal time scale, and indicate that suitable sea water temperature might be the main forcing of anchovy migration. This work also demonstrates the potential of predicting changes in fish population based on climate records. [ABSTRACT FROM AUTHOR]

The Yellow Sea (YS) is a semi-enclosed marginal sea in the West Pacific. As part of the China GLOBEC-IMBER program, the present study set out to investigate the mechanisms involved in the seasonal patterns of phytoplankton biomass and community structure in the southern YS. During four cruises in April and October 2006, and March and August 2007, the phytoplankton spring bloom, the Yellow Sea Warm Current (YSWC) and the Yellow Sea Cold Water Mass (YSCWM) were the most remarkable biogeochemical events in the study area, involving significantly different phytoplankton communities. During cold seasons nutrient-rich water was observed, coincident with the occurrence of the YSWC, which is considered to be warm and saline water from the northward Kuroshio branch current (Cheju Warm Current). However, low Chl a concentrations (< 0.6 mg m − 3 ) and a high relative abundance of prasinophytes (29% of Chl a , average value of the euphotic zone, and the same below) were observed in the YSWC area in March. During April a spring bloom occurred with very high concentrations of Chl a (7.69 mg m − 3 ) and fucoxanthin (1.98 mg m − 3 ), and was dominated by diatoms. The mechanism and processes of the spring bloom in the central YS are very complex and possibly unique, and the YSWC affects the distribution of nutrients and hydrological environment for phytoplankton growth. Low Chl a biomass (0.2 mg m − 3 ) and a low contribution of diatoms, but a high contribution of cyanobacteria (36%) were observed in the stratified central YS in August when the YSCWM prevailed, and a high relative abundance of chrysophytes (38%) was observed in October when the YSCWM was decaying. In a word, significant seasonal variations of phytoplankton biomass and community structure were observed in the central rather than the coastal area. These results were considered as the physical–chemical–biological characteristics of the unique ecosystem in the central YS. [ABSTRACT FROM AUTHOR]