| Scomber japonicus is one of the main commercial fish in the northwest Pacific Ocean,which plays an important role in Marine fishery in China.The early life history of Scomber japonicus will be affected by many environmental factors.Climate change and changes in marine environment will have an impact on the growth and development,transportation distribution and resource recruitment of Scomber japonicus.The change of marine environment caused by climate change will have a great impact on Scomber japonicus resources.Different scholars have reached different conclusions on the influence of El Ni(?)o and La Ni(?)a events on Scomber japonicus stock,and the dynamic factors of physical environment on Scomber japonicus stock are still unclear.Therefore,based on the understanding of the biological characteristics of Scomber japonicus,the relationship between early life history and environmental factors,the survival and growth of environmental changes on its early life history,the impact of resource recruitment,and the application of relevant ecological models on Scomber japonicus,FVCOM physical model and individual based model are coupled by Lagrange mass point method,The early ecological dynamics model of Scomber japonicus in the Northwest Pacific based on individual model was constructed.This model is used to simulate and study the transportation distribution and resource recruitment in the early life stage of Scomber japonicus in the Northwest Pacific from 1997 to 2010,and analyze its transportation distribution and the general change of resource recruitment under abnormal climatic conditions.The established model can better simulate and predict the transportation distribution and early recruitment of Scomber japonicus,providing scientific basis for resource management and reference significance for the development strategy of Scomber japonicus fishery.The simulation results show that:(1)The individual-based ecological dynamics model of the early life history of Scomber japonicus in the Northwest Pacific,which is constructed in this paper,can better simulate the early growth rate,transport trend,abundance distribution and resource recruitment of the Scomber japonicus in the Northwest Pacific.And it is basically consistent with the previous research results,so the parameters set in the model are reliable,and the model can lay a foundation for the further study of Scomber japonicus fishery resources.(2)In terms of transport and distribution of Scomber japonicus,the ocean circulation plays a decisive role in the transport and distribution of Scomber japonicus eggs and larvae in the Northwest Pacific.The Kuroshio and parent tide have a great impact on the transport and distribution of Scomber japonicus eggs and larvae.From the beginning to the end of the simulation,the 14-year transport trend and abundance distribution are basically similar.From March to July,the eggs and larvae have been passively transported along the direction of the Kuroshio current.In the horizontal direction,in March along the Kuroshio main axis,it transports to the east and northeast.From April to July,it transports eastward along the Kuroshio system.In June to July,the mate tide suppresses the larvae and continues to transport northward.The main driving force for this transportation is to concentrate 4/5 of the larvae and juveniles in the Kuroshio Sustaining River Basin and the excellent feeding grounds in the KuroshioMyotanic transition area for fattening.Finally,the larvae and juveniles are widely distributed in the Kuroshio Sustained River at the end of July.Watershed,KuroshioOyashio transition area;In the vertical direction,the eggs and larvae will be held by the Kuroshio to deeper waters over time.(3)Regarding the recruitment of Scomber japonicus,there have been large fluctuations in 14 years,indicating that changes in the physical environment have a great impact on the recruitment of Scomber japonicus resources in the Northwest Pacific.However,the situation of recruitment in the same month in 14 years is basically similar:The highest mortality rate occurs from the end of March to the end of April.At this stage,more than 90% of the total number of fish eggs and larvae died.Therefore,the increase in water temperature in April is beneficial to the Northwest Pacific.Increase in recruitment of Scomber japonicus;Since May,the mortality rate has gradually decreased,and the extent of the reduction in recruitment has become smaller.From June to July,due to biological factors and environmental factors,the mortality rate of larvae and juveniles decreased,and the downward trend of recruitment decreased more obviously.(4)In terms of the impact of climate change on fish eggs and larvae in the Northwest Pacific,different climates have different impacts on their transport distribution and resource recruitment.Compared with normal years,the distribution range of eggs and larvae of Scomber japonicus in the Northwest Pacific Ocean during the medium-intensity El Ni(?)o year is wider,and the amount of resource recruitment is higher;while the distribution range of the medium-intensity La Ni(?)a year transport is relatively small.The amount of resource recruitment is low.Although the eggs and larvae of Scomber japonicus in the Northwest Pacific in the El Ni(?)o year are transported to deeper waters,the temperature at the location is higher,and the amount of resource recruitment will increase compared with normal years;the opposite is true in the La Ni(?)a year.Although the place where the larvae and juveniles are transported is not as deep as the El Ni(?)o year,the temperature in the place is low,and the amount of resource recruitment will be less than in normal years.(5)After moving the spawning ground to the west,the general transportation direction of the eggs and larvae is basically similar to the transportation direction and route of the main spawning ground in the Izu Islands.In the horizontal direction,it was transported to the east and northeast with the Kuroshio in March,and it was transported to the east with the Kuroshio from April to July.At the end of July,it was widely distributed in the Kuroshio to Oyashio transition area for bait;In the vertical direction,the eggs and larvae will gradually be held by the Kuroshio to deeper waters.However,from the perspective of juvenile abundance distribution,most of the larvae and juveniles gather at a different location from the Izu Islands,only partially overlapping areas.Moreover,after moving westward,there are endless and irregularly-shaped islands in the northeast of the spawning ground.The eggs and larvae in this area are affected by the current and are easily swept to the coast by the current.It can survive and grow,and the mortality rate is extremely high.Therefore,the recruitment of Scomber japonicus resources in the Northwest Pacific after the spawning ground moves westward is relatively low.(6)When the spawning depth changes,the transport trajectories of eggs and larvae are almost the same as the final distribution position,and only a few super individuals are different.Therefore,in a certain range,the change of spawning water depth has little effect on the transportation process and final resource distribution position of Scomber japonicus larvae and juveniles.However,through the impact on the recruitment,it is found that the change of spawning depth has a great impact on the final resource recruitment.The simulation results show that the recruitment amount at the spawning depth of 5m is more than 10 m,15m and 20 m.However,because temperature is the most key factor affecting the final resource recruitment amount of Scomber japonicus,the spawning in the shallow water layer with higher temperature is conducive to the increase of the final resource recruitment amount in the critical period of the survival of fish eggs and larvae that are very sensitive to the marine environment.However,from the perspective of average mortality,the mortality in water depth of 10 m is the lowest,and the spawning depth of 10 m is the best spawning depth of Scomber japonicus in the Northwest Pacific. |
