Simulation of the distribution, growth, and survival rate of chub mackerel larvae and juveniles in the East China Sea

In the East China Sea (ECS), chub mackerel Scomber japonicus constitutes an important coastal-pelagic fishery resource that is mainly exploited by Chinese, Japanese, and Korean light-purse seine fisheries. Because the early life history of chub mackerel plays a significant role in its recruitment, we developed an individual-based model to study the distribution, growth, and survival rate of chub mackerel larvae and juveniles in the ECS to improve our understanding of the chub mackerel population structure and recruitment. Our results show that as body length rapidly increases, the swimming capacity of chub mackerel larvae and juveniles improves quickly, and their spatial distribution depends more on their habitat conditions than the ocean currents. Correspondingly, the juveniles from the central and southern ECS spawning ground are scarcely recruited into the Japan/East Sea (JES) or the western Pacific Ocean, but a significant proportion of juveniles from the northern ECS spawning ground still enter the JES and there are exchanges between the stocks in the ECS and JES. Thus, it seems more reasonable to assess and manage the chub mackerels in the ECS and JES as a stock. The water temperature and ocean primary production in the ECS are two important factors influencing the chub mackerel habitat conditions and their spatial and temporal distribution are significantly different as the spawning time changes. Therefore, the spawning time and location play an important role in the growth and survival rate of the larvae and juveniles. Generally, when chub mackerel spawns at the southern ECS spawning ground in March, the larva and juvenile growth and survival rate is relatively high; as spawning time moves forward, higher growth and survival rates would be expected for the chub mackerel spawned coastward or northward. For specific spawning sites, early or delayed spawning will reduce the survival rate.