Distribution of the age 0 group Pacific cod (Gadus macrocephalus) in the Yellow Sea and its relationship with environmental factors

Pacific cod Gadus macrocephalus is distributed around the rim of the North Pacific Ocean, and it’s considered as an ecologically important species. Studies on the biological characteristics and distribution patterns of juvenile Pacific cod would be helpful to understand cod population dynamics. Based on the data collected during the fishery resources surveys carried out in June, August, October and December 2016, the growth of the age 0 group Pacific cod in the Yellow Sea was studied, and the generalized additive model (GAM) was used to analyze the distribution characteristics and their relationship with environmental factors of the age 0 group Pacific cod. The results showed that the age 0 Pacific cod was allometric. Growth rate of the body weight was not equal to the body length, and the weight gain was faster. Allometric factor b was 3.3161. The age 0 group Pacific cods in the Yellow Sea were distributed in the waters in bottom salinity range of 31.7 to 33.3, in bottom water temperature range from 6.6 to 12.1 °C and in depth range of 35.8 to 87.2 m. The favorite sediment in the nursery habitats was fine silty sand and soft clay mud. The seasonal variation in the distribution pattern of the age 0 group Pacific cod was synchronized with the seasonal variation of the Yellow Sea cold water mass. The environmental factors which had significant effects on the ecological density of the cod juvenile were in the order of bottom water temperature, sediment and bottom salinity,while the depth had no significant influence on the juvenile density.