Basic Biological Property And Spatiotemporal Dynamics In Fishing Ground Of Scomber Japonicas In North Pacific High Seas

With the overfishing of fish resources in China’s offshore,the supply of the offshore resources can not meet the growing demand of the consumers.It is an important solution to supply the domestic market by catching economic fish species from the high seas around the world while protecting the fish resources offshore.Chub mackerel is one of the most important fishing species of light-purse seine and light lift net fishery in North Pacific high seas.It is a warm-water,middle upper and long-range migratory fish,widely distributed in the coastal waters of the Northwest Pacific Ocean and has a large number of resources and which migratory is greatly affected by the marine environment.It will make sense for us to take advantage of the resource if we explore its basic biological features and the relationship between its spatiotemporal and the marine environment.Ac-cording to the basic biological data of chub mackerel collected from North Pacific high seas in Oct.to Nov.2016 and Apr.to Nov.2017,biological characteristics such as the stock composition,female to male ratio and feeding intensity were studied.Resource abundance,change of time and space of fishing ground centroids and the relationship with influential environmental factors of chub mackerel were analyzed with the method of production gravity center,statistical interpolation,Through environmental data like the sea surface temperature（SST）,sea chlorophyll-a（Chl-a）concentration and ocean current got by satellite remote sensing inversion technology and monthly trawling and purse seine product data of chub mackerel in North Pacific high seas in 2014²016.The main results can be summarized as follows:（1）Basic biological characteristics of chub mackerel in North Pacific high seas was analyzed.The results show that the fork length of the stock ranged from 130mm to378mm with an average value of 226.08mm,and the dominant group ranged from 161mm to 210mm and 271mm to 300mm.The weight of the female stock ranged from 23.7g to837.2g with an average value of 144.59g,and the dominant group of which ranged from50g to 100g and 200g to 300g.The weight of the male stock ranged from 22.5g to 740.6g with an average value of 148.36g,and the dominant group of which ranged from 0 to150g and 200g to 250g.Females to males conformed to a ratio of 1:1 in different fork length and different seasons,while female fish out-numbered male ones significantly in the weight range from 200³00g.（2）The result of its feeding habits turns out that diet of chub mackerel in North Pacific Ocean included 9 taxa and 16 prey species,and was dominated by shrimps.In the taxonomic level of species,the dominant preys were the Euhausiacea sp.For shrimp’s items,the unidentified fish and Sardinops sagax for fish’s items.The fish prey had rela-tively higher weight percentage W（%）and lower numeric percentage value compared with the shrimps.There is no significant change in feeding intensity and stomach fullness index P（%）when the fork length less than 300mm or the weight less than 300g,on the other hand,feeding intensity and stomach fullness index P（%）tends to increase when the fork length greater than 300mm or the weight greater than 300g.Universally,the chub mackerel feeding more large bait and have lower trophic niche when its fork length greater than 300mm.（3）The study of the distribution and the relationship with marine environment indi-cated that the fishing ground of chub mackerel have significant seasonal differences,and the gravity center of fishing ground distributed in the range of 39°N⁴3°N、147°E¹54°E,which moved from northeast to southwest at September.Generalized additive models（GAM）indicates that optimal sea surface temperature of chub mackerel is 14¹7℃,optimal chlorophyll-a concentration is 0.3⁰.5mg·m^-3,and the space distribution is centralized in 40°N⁴1°N、148°E¹51°E in North Pacific Ocean.Sea current is important for the formation of chub mackerel fishing ground.The innovation of this research is mainly reflected as followed:（1）Using the biological data sampled in the same period of two years of chub macke-rel to obtain the characteristics of the growth in the sea area,and provide a reference for more rational use of its resources in the future.（2）Using the product data to reflect the fishing ground of chub mackerel.（3）The relationship between the distribution of fishing ground of chub mackerel and the marine environment is discussed in detail,and the best environmental factors for chub mackerel is obtained.