| Chub mackerel(Scomber japonicus)is a kind of warm oceanic mid-pelagic migratory fish,which is not only distributed in Pacific and Atlantic Ocean,temperate zone of Indian Ocean and subtropical continental shelf sea area,but also widely distributed in the East China Sea and Yellow Sea.At present,Chub mackerel has become one of the main economic species of mid-pelagic fish resources in the East China Sea and Yellow Sea,which plays an important role in marine fishery.However,the catches of Chub mackerel of China fluctuate and decrease with years in recent years.Furthermore,the population structure has become younger and miniaturized in the East China Sea and Yellow Sea,which may be related to overexploitation and unsuitable marine environmental conditions.At present,it is a serious problem how to reasonably and sustainably utilize the fishery resources of chub mackerel in the East China Sea and Yellow Sea.Therefore,it is necessary to use relevant models and marine environmental data to study temporal and spatial distribution and formation mechanism of fishing grounds and to analyze reasons for changes of fishery resources of Chub mackerel in the East China Sea and Yellow Sea.The study will provide a scientific basis for the rational and sustainable utilization of the fishery resources in the East China Sea and Yellow Sea.In this study,the IBM model is used to construct a physical-biological coupling model of spatial distribution of Chub mackerel in the East China Sea and Yellow Sea based on individual-based model.This model and related marine environmental data are used to simulate the spatio-temporal dynamic distribution of Chub mackerel in the East China Sea and Yellow Sea.This study mainly shows the spatial distribution of Chub mackerel(age>1 year),spawning Chub mackerel and the eggs,larvae and young,the influences of biomass on spatial distribution,the effects of ability to swim of larval and young to its spatial distribution,the changes of spawning water temperature for spatial distribution of spawning Chub mackerel,the influence of time interval on results of model in four scenarios.This study discusses the relationship between simulation time,data quality,model structure and results,the rationality of spatial distribution,diurnal vertical migration,spawning,growth,parameters setting of Chub mackerel and limitations of this study.The results of this study can be applied to the analysis of the influence of fishing intensity,the influence of marine environment changes on the spatial distribution and evolution of Chub mackerel and the resource changes of Chub mackerel.This study provides a reference basis for the evaluation of the fishery management strategy,the prediction of the fishing situation and the sustainable utilization of fishery resources of Chub mackerel in the East China Sea and the Yellow Sea.The main results are as follows:(1)This model can systematically simulate the temporal and spatial distribution of Chub mackerel(age>1 year),spawning Chub mackerel and the eggs and larvae of Chub mackerel in the East China Sea and Yellow Sea.The model results show that:(1)The overwintering locations of Chub mackerel(age>1)are mainly distributed along the line from Taiwan Strait to Tsushima Strait in winter.In spring,with the increase of water temperature,Chub mackerel(age>1 year)migrate to coastal waters,Yangtze River estuary and Sea of Japan to spawn and feed.In summer,Chub mackerel(age>1 year)are widely distributed in East China Sea and Yellow Sea.In autumn,with the decreases of water temperature,Chub mackerel(age>1 year)migrate from the shore to the open sea,and return to the overwintering ground again in winter.(2)The spawning period of Chub mackerel in the East China Sea and Yellow Sea is from February to August.In February,the locations of spawning grounds and its wintering grounds of Chub mackerel are the same.In March,the distribution of spawning Chub mackerel is closer to shore.In April,spawning Chub mackerel are widely distributed in the coastal waters and offshore of Zhejiang and Fujian province,the south of Jeju Island and the southwest of Kyushu Island.Spawning Chub mackerel are also distributed in the coastal waters of Jiangsu Province in May.In June,spawning Chub mackerel are also found in Jiaozhou Bay and the southern west coast of the Korean Peninsula.In July,spawning Chub mackerel begin to appear in the northern Yellow Sea and the west coast of the Korean Peninsula.The spawning population mainly distributed in the coastal waters of the Yellow Sea in August.(3)Spatial distribution of eggs and larvae of Chub mackerel are not only closely related to the spatial distribution of spawning population,but also affected by ocean currents.From February to March,eggs and larvae of Chub mackerel are mainly distributed in the open sea in the East China Sea and the southwest of Kyushu Island.Due to the influence of Taiwan Warm Current and the marginal current of Kuroshio,the eggs and larvae of the southern part of the East China Sea are carried by the current to the south of Jeju Island,southwest of Kyushu Island and the Pacific Ocean,then gather in the south of Jeju Island and southwest of Kyushu Island,and some of the larvae enter the Sea of Japan.From April to May,many eggs and larvae are distributed along the coast of Zhejiang and Fujian province,and are transported to the Yangtze Estuary by the Taiwan Warm Current and the Coastal Current.The aggregation occurs in the Yangtze Estuary.From June to July,the eggs and larvae of Chub mackerel are distributed in the coastal areas of Zhejiang Province,the Yangtze River Estuary,Jiangsu Province and Shandong Province.In August,there are also a few eggs and larvae of Chub mackerel in the west coast of North Korea and the northern Yellow Sea.In addition,the early young stage of Chub mackerel are mainly distributed in the waters off Zhejiang Province and the southwest of Kyushu Island in May.In June,the early young stage of Chub mackerel are mainly distributed in the coastal and offshore waters of Zhejiang Province,the south of Jeju Island and the southwest of Kyushu Island.From July to September,the early stage of Chub mackerel gradually spread to the northern Yellow Sea,the southern East China Sea and the Sea of Japan.(2)The resource density will affect the spatial distribution of Chub mackerel.When the stock of Chub mackerel is set at 0.3 million tons,there are significant differences in the spatial distribution of Chub mackerel(age>1),spawning Chub mackerel and eggs and larvae when the stock is 1.5 million tons.For example,When the stock of Chub mackerel is set at 0.3 million tons,the time of entering the coastal waters of Zhejiang province,Jiaozhou Bay and Yellow Sea is delayed.(3)Swimming ability will affect the spatial distribution of larvae and young of Chub mackerel.When the swimming ability of larvae and young is ignored,the influence of ocean current is more obvious.Most of larvae and young of Chub mackerel hatched off the southern waters of the East China Sea are transported to the Pacific Ocean and the Sea of Japan,while larvae and young of Chub mackerel hatched off the southern waters of the East China Sea are transported by the Taiwan Warm Current and the Coastal Current to the waters off Zhoushan Islands,and stay in the Yangtze River dilute water area for a longer time,and the detention effect is more obvious.When the swimming ability of larvae and young of Chub mackerel is considered,a small number of individuals could bypass the dilute waters of the Yangtze River and enter the southern waters of Jeju Island,thus affecting the spatial distribution of Chub mackerel in the East China sea and Yellow sea.Therefore,the swimming ability of larvae and young of Chub mackerel must be taken into account in the simulation.(4)The decrease of spawning water temperature affects the spatial and temporal distribution of spawning Chub mackerel.When the spawning temperature decreases,the proportion of spawning population increases significantly from February to April while the proportion of spawning population decreases significantly from June to August.Due to the increase of spawning populations from February to April,the eggs quantity of Chub mackerel into the Sea of Japan and the Pacific Ocean increases,which lead to the difference of the stock and spatial distribution of Chub mackerel.(5)When the time interval of 1200 s is set,there are certain differences in the simulation results compared with the results of time interval 21600 s.When the time step is set at 1200 s,the arrival time of Chub mackerel(age>1 year)into the coastal area of Zhejiang Province,Jiaozhou Bay and Yellow Sea is delayed,which results in different temporal and spatial distribution of spawning populations,affecting the spatial distribution of larvae and young of Chub mackerel.However,from the overall simulation results,except for diurnal vertical migration,the simulation result of 21600 s is more reasonable than that of 1200 s. |
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