Effect of regional warming on the abundance of Pseudeuphausia sinica Wang et Chen (Euphausiacea) off the Changjiang River (Yangtze River) Estuary

Distribution and abundance of Pseudeuphausia sinica off the Changjiang River Estuary (30°00'-32°00'N, 122°00'-123°30'E), the East China Sea were studied in relation to environmental features associated with the regional warming. P. sinica is a subtropical species. Off the Changjiang River Estuary, its abundance reached maximum in summer. To examine spatial and temporal changes of P. sinica off the Changjiang River Estuary, the authors have combined all available sampling data in 1979, 1981, and 2000-2007. This database shows that a significant increase in abundances of P. sinica was observed in spring of 2000-2007 as compared with 1979, 1981. The abundance of P. sinica increased from 0.18-0.21 ind./m³ in 1979 and 1981 to 0.68-4.00 ind./m³ in 2000-2007. Accordingly, the sea temperature increased obviously from spring of 1979, 1981 to the 2000s. The authors further found a positive relationship between average surface temperature and average abundance of P. sinica. Regional warming, together with the release of predator induced stress due to a sharp decline in the abundance of its predator (e.g., fishes), were thought to be responsible for the increase in abundance of P. sinica in water off the Changjiang River Estuary.