동중국해에서의 살오징어(Todarodes pacificus) 유생의 여름 발생과 수송과정에 관한 연구

Abstract

To reveal the summer patterns of horizontal distribution and transport process of common squid paralarvae, totals of 218 larvae were collected at 63 stations in the northeastern East China Sea during July 2006 and 2007. Most paralarvae were occurred in the southeast of Jeju Island and north of Kyushu where water temperature and salinity at 50 m and surface chlorophyll-a concentration ranged 15-22 ℃, 32.7-34.6 psu and 0.13-0.77 mg/m³, respectively. Mantle length range of the paralarvae was 1.0-9.5 mm. Based on relationship of environmental factor and larval abundance, optimal environmental condition of larval occurrence was estimated in 18-22 ℃, 32.8-33.3 psu, 0.63-0.79 mg/m³. Potential spawning areas have been inferred by seawater temperature data at 50 m depth from NODC, KODC, JODC and GIS bathymetry data, assuming that eggs and hatchlings occur over the outer shelf and continental slope (100-500 m) at temperature range of 18-23 ℃. The results showed that successful potential spawning area during summer was located from the north of 29°N to Noto Peninsula. Regional Ocean Modeling System (ROMS) based on reanalyzed data during 1993-2002 was applied to track transport paths of eggs and paralarvae in summer. The numerical experiment indicated that most of eggs and paralarvae were transported to the East Sea through the Korea Strait, and it takes about 10-60 days from inferred spawning area to southwest of the East Sea. Also, various current patterns according to releasing dates resulted in entrainment of squid larvae into the Yellow Sea and the coast of South Sea. Considering the transport paths and paralarval size, we found the local spawning stock in summer might be common in the northeastern East China Sea. The Change of abundance between 2006 and 2007 seemed to be induced by annual variation of Changjiang diluted water and Tsushima warm current.