| Chub mackerel(Scomber japonicus)is a warm-water pelagic migratory fish found mainly in the Pacific,Atlantic and Indian Oceans and their coastal waters,and is mainly harvested by China,Japan and Korea.In recent years,chub mackerel has become one of the major economic fish species in China and occupies an important position in marine fisheries.The problems of chub mackerel,such as miniaturization of the fish catch,younger age of catch composition,increased fluctuations in production and decreasing year by year,mean that chub mackerel resources may have been overexploited.Therefore,research on the population structure,growth,survival rate,and resource assessment of Chub mackerel should be strengthened to provide a scientific basis for sustainable development and scientific management of the species.In this paper,an individual-based model was constructed to simulate the growth,mortality,and swimming behavior of chub mackerel larvae and juveniles in the East China Sea based on a summary of the life histories of chub mackerel in the literature.We use this IBM,which combine with three-dimensional marine environmental data to investigated the spatial and temporal distribution of the chub mackerel larvae and juveniles.This paper mainly shows the effects of swimming behavior,pattern of egg release,and biomass of chub mackerel on the spatial-temporal distribution,death and survival simulation of its young fish under five scenarios.We also analyzed the relationship of the distribution,growth and survival rate with the marine environment and the uncertainty of the model to deepen the understanding of the recruitment and stocks of chub mackerel in the East China Sea.What’s more,based on the determined stock structure,a Bayesian biomass dynamics model was used to assess the chub mackerel in the East China and Yellow Sea using catch data from China,Japan,and Korea.The effects of stock structure on the stock assessment,uncertainty of data,the abundance index data,and priors settings on the resource assessment of chub mackerel in the East Yellow Sea were analyzed.The results of this paper can provide a reference basis for the evaluation of the fishery management strategy,the prediction of the fishing situation and the sustainable utilization of the fishery resources of chub mackerel in East China and the Yellow Sea.The main results are as follows:(1)In the IBM simulation of chub mackerel larvae in the East China Sea:the spatial distribution of juvenile chub mackerel is influenced by current transport,but 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;when there is habitat competition,the spatial distribution of chub mackerel in different spawning grounds may be segregated.The growth and survival of juvenile chub mackerel depend on spawning time and location.As the spawning month progresses,the growth and survival rates of juvenile chub mackerel decrease in the southern spawning grounds of the East China Sea due to the Kuroshio system,while the survival rates of juvenile chub mackerel increase in the northern spawning grounds due to the increase in water temperature and ocean primary productivity.Increased survival increases competition for bait among juveniles,which in turn decreases the growth rate of juveniles.Water temperature and ocean primary productivity are important factors influencing the variation of chub mackerel supplementation,but the magnitude of chub mackerel supplementation depends on the match between spawning location,spawning time,and water temperature and ocean primary productivity.The modeling results indicate that a large number of juvenile from the northern spawning grounds enter the Japan/East Sea,and a small number of juveniles enter the eastern Pacific coast of Japan.Based on this,this paper suggests that the stock assessment of chub mackerel,which in the East,Yellow Sea and Japan/East Sea,should be as a population.(2)In the stock assessment of chub mackerel in the East and Yellow Seas using Bayesian biomass dynamic model:the stock classification of chub mackerel in the Eastern and Yellow Seas is still controversial,and the assumption of two stocks would overestimate the total maximum sustainable yield,which would be detrimental to the recovery of chub mackerel resources;chub mackerel in the Eastern and Yellow Seas are already overfished,and if the probability of chub mackerel not being overfished in 10years is to exceed 60%,the TAC(Total Allowable Catch)should be set below 4.82×10~5 t,i.e.,the catch should be reduced by 0.85×10~5t from the 2019 catch;when the quality of fisheries data is poor or the model parameterization is unreasonable,the Bayesian biomass dynamic model model relies more on the a priori assumptions of the parameters,and the a priori setting has an important impact on the results of the resource assessment,as there is a significant negative correlation between r and K,which makes it impossible to obtain reasonable and the accuracy of the catch data observation error has an important influence on the parameter estimation of the Bayesian biomass dynamic model;because of the controversial status of chub mackerel populations in the East and Yellow Seas and the difficulty of poor quality of fishery data,the results of the chub mackerel simulations in this paper also indicate that there is a possibility of connectivity between the young and juvenile chub mackerel in the East and Yellow Seas.Therefore,this paper assesses chub mackerel as a single stock in the East and Yellow Seas to meet the basic assumptions of the Bayesian biomass dynamic model and to improve the quality of the assessment of this fishery. |
