brackish waters.
For Hiromi & Ueda (1987, p.23) the species, first discovered in the Whanpoo River, Shanghai, is restricted to brackish waters along the coasts of the Yello Sea and East China Sea. In Japan, there are several records, but it is not certain weither this copepod is conspecific to S. sinensis. the species seems stricktly restricted to the northernmost part of Ariake-kai. It is less likely that the species has been introduced to Japan by ocean currents and also by ships-transport, because the ports in the northern part of Ariake-kai are not so large. Considering the geological history of the Japanese Islands and the characteristics of the fauna in Ariake-kai, it is most likely that the species is a continental relict. Before the Würm glacial period, when Japan was linked to the Continent of China as a result of regression, the Chinese population could have spread out in the northeasterly direction because the East China Sea at that time was mostly covered with brackish water. Later, about 6,000-10,000 years ago, Japan began to be isolated as the sea level rose with the Jômonian transgression and an isolated population would have remained in Ariake-kai.
The Ariake-kai specimens need to be compared with the Chinese ones; a comparative study may show geographic divergences.
After Ohtsuka & Nishida (2017, p.579), the brackish species , aggregated just above the bottom in submerged channels outside the mouth during heavy flooding. Losses from the population, in particular of immature copepodids, were compebsated by reproduction after the flood. Relationships between feeding behavior of fish juveniles and the distribution of planktonic copepods have been investigated in the mouth of Chikugo River (Kyushu, Japan). Larvae and early juveniles of Japanese temperate bass Lateolabrax japonicus migrate to the turbid, low-saliniry area of the river, where the prey upon the abundant calanoid Sinocalanus sinensis (See Hibino & al., 1999; Suzuki @ al., 2008)