Spawning Ecology of Maurolicus japonicus in the Korea Strait and the Ulleung Basin

Abstract

In order to investigate the spawning ecology of M. japonicus in the Korea Strait (KS) and the Ulleung Basin (UB), we collected the eggs and larvae of M. japonicus, and measured the water temperature and salinity from 1992 to 2003. We analyze the distribution pattern on the eggs and larvae, and the density changes and distribution pattern according to the developmental stages of eggs. There were two types of water masses such as the Tsushima Warm Current (TWC) and the Korea Strait Bottom Cold Water (KSBCW). Their two currents were opposite in flow direction. M. japonicus was a year-round spawning between the KS and the UB. The eggs were mainly distributed in the UB and the northern Korea Strait (NKS) including the western channel. The distribution range of eggs was widely in the fall but most narrowly in the winter. The range of egg density was 1.0235 to 1.0266g/cm3, which was increased as eggs developed. The egg density was higher than that of the surface water but similar to the ambient water in 55-140m depth. The composition of eggs with early, middle, and late developmental stages had similar ratios to each other in the NKS. But the relative egg ratios of the middle and late developmental stages were slightly increased into the western KS away from the NKS located in the southern Ulleung Basin (SUB). The distribution pattern of larvae was similar to those of eggs. But the larvae were not found in the WKS and only e the distribution pattern on the eggs and larvae, and the density changes and distribution pattern according to the developmental stages of eggs. There were two types of water masses such as the Tsushima Warm Current (TWC) and the Korea Strait Bottom Cold Water (KSBCW). Their two currents were opposite in flow direction. M. japonicus was a year-round spawning between the KS and the UB. The eggs were mainly distributed in the UB and the northern Korea Strait (NKS) including the western channel. The distribution range of eggs was widely in the fall but most narrowly in the winter. The range of egg density was 1.0235 to 1.0266g/cm3, which was increased as eggs developed. The egg density was higher than that of the surface water but similar to the ambient water in 55-140m depth. The composition of eggs with early, middle, and late developmental stages had similar ratios to each other in the NKS. But the relative egg ratios of the middle and late developmental stages were slightly increased into the western KS away from the NKS located in the southern Ulleung Basin (SUB). The distribution pattern of larvae was similar to those of eggs. But the larvae were not found in the WKS and only