Abstract
Grazing and metabolism of Euphausia pacifica in the Yellow Sea were studied from September 2006 to August 2007. Euphausia pacifica is a selective-feeding omnivore and grazing rates among different months were monitored using a Coulter Counter and batch culture feeding experiments. Euphausia pacifica mainly grazed microzooplankton in August and September, which resulted in an increase in chlorophyll a concentration. Oxygen consumption rate of E. pacifica was 38.7–42.5 μmol O2 g-1 DW h-1 in March, which was four times higher than the oxygen consumption rates in September and December. The vigorous metabolism of E. pacifica in March consumed 3.1% of body carbon daily, which is likely related to its high reproduction and grazing rate. Respiration and metabolism of E. pacifica in September and December were similar and were lower. O:N ratio of E. pacifica was the highest (17.3–23.8) in March when spawning activity occurred and when food was abundant. The energetic source of E. pacifica during September and December was mostly protein from eating a carnivorous diet, including such items as microzooplankton. Euphausia pacifica was found in cold water at the bottom of the Yellow Sea in summer and autumn and maintained a low consumption status. O:N ratios of E. pacifica in March, September, and December were negatively correlated with SSTs and no significant correlation was found between O:N ratios and chlorophyll a concentration. Seawater temperature is clearly the most important parameter influencing the metabolism of E. pacifica.
Highlights
As one of six important euphausiids species being commercially harvested, Euphausia pacifica is a large pelagic crustacean and is widely distributed in the North Pacific Ocean and adjacent coastal waters [1,2,3,4,5]
When the water column was vertically mixed in March and December, surface and bottom water temperature and salinity were similar and stable and the differences in seawater temperatures were less than 2.0°C
Ohman found that E. pacifica was a selective-feeding omnivore in experiments with diatoms and copepods [24]
Summary
As one of six important euphausiids species being commercially harvested, Euphausia pacifica is a large pelagic crustacean and is widely distributed in the North Pacific Ocean and adjacent coastal waters [1,2,3,4,5] It is regarded as the key predominant euphausiid species in the Yellow Sea [6,7], where it constitutes more than 50% of the biomass of the large crustaceans (body length > 5 mm) throughout the year and nearly 80% in spring [8]. Euphausia pacifica is a key pelagic grazer [9] and the main food of many commercial fish in the Yellow Sea, especially adult anchovy [10,11] It is harvested for human consumption and as an additive for aquaculture feed [12]. In the Yellow Sea ecosystem, E. pacifica is regarded as one of the most important
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
