A comparative study on the ecological characters of Corbicula japonica populations inhabiting at the subtidal estuary of the Seomjin River and the intertidal Eulsuk sand flat of the Nakdong River, Korea
Jin-Young Seo, Jeong-Hyeon Kim and Jin-Woo Choi
Risk Assessment Research Center, KIOST, 41 Jangmok 1-gil, Geoje 53201, Republic of Korea
For the comparative investigation on the ecological characters of the brackish water clam, Corbicula japonica populations inhabiting at the Seomjin River estuary (SRE) and the Eulsuk tidal flats (ETF) in Nakdong River estuary, the sampling was performed by monthly from Mar. to Nov., 2017. The habitats of Corbicula populations in the SRE and the ETF consisted of sand more than 80%. The mean salinity of the SRE and the ETF was 17 psu and 20 psu, respectively. The average shell length of C. japonica was about 10 mm in the SRE, but more than 20 mm in the ETF. However, the density of C. japonica was more than 30 times higher in the SRE. The optimal salinity for the filtration activity of C. japonica was observed from 5 to 15 psu in the SRE, but that in the ETF was observed up to 30 psu. The growth rate of C. japonica in SRE was relatively higher than that of ETF, especially it was higher from April to August. In SRE, spats with the shell length of 2 mm were observed from April, and the density of 2-4 mm individuals rapidly increased in May. In both the SRE and the ETF, the highest density of Corbicula spats was found in July, 2017. From the histological observations on gonadal organs, individuals with spent stage were observed in June, 2017. This suggests that the recruitment of C. japonica would be happened before June.
  
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