| Chub mackerel(Scomber japonicus)is a warm water and pelagic species,which is widely distributed on Pacific Ocean,Indian Ocean,Atlantic tropical and subtropical regions and coastal waters.Chub mackerel is also distributed in the coastal waters of China,Japan,Korea,where it is an important catch in fishing object of the light purse seine fishiers(LPSF).The miniaturization of fish catch has been intensified,the composition of fish catch has become younger and the output of this fish catch has been fluctuated obviously in recent years.These phenomenona indicate that Chub mackerel resource may have been overfished.Therefore,we need to strengthen the investigation of the habitat and stock assessment of Chub mackerel in order to ensure the sustainable utilization of Chub mackerel resources and the guidance of fishery management.This study analyzed the temporal-spatial changes of the fishing location and the number of fishing vessels in the East China Sea and Yellow Sea basing on the VIIRS Boat Detection data of the Visible Infrared Imaging radiometer sensor of Suomi National Polar-orbiting Partnership satellite(2013 to 2017),the data of marine environment of the East China Sea and Yellow Sea and literatures of the fishery resources,the distribution of fishing groundsand the measures of fishery management.We also further discussed the relationship between the remote sensing data of fishing boat lighting and the spatial distribution of Chub mackerel.In addition,basing on the statistical data of Chub mackerel from 1997 to 2015 and environment data(e.g.sea surface temperature,chlorophyll-a concentration and sea surface height),we standardized the nominal CPUE(catch per unit fishing)of by using the generalized additive model(GAM)and built a variety of spatial weighted standardized CPUE by utilizing the assumption of the resource abundance of the unfished grids.Meanwhile,we discussed the rationality and relationship of standardized CPUE by GAM and spatial weighted standardized CPUE.Finally,we assessed the stock of Chub mackerel and analyzed the effects of different TAC on fishery resource status by using the software of JABBA(Just Another Bayesian Biomass)andthe catch data of China,Japan and Korea,standardized CPUE and Schaefer surplus yield model.The results of this study can provide references for fishery management of Chub mackerel in the East China Sea and Yellow Sea.They are as follows:(1)Fishing vessel data could reflect the temporal and spatial distribution of fishing activities and fishery resources in the East China Sea and the Yellow Sea,for example,the distribution of fishing vessels in the north fishing region had been greatly reduced because of weather and the Spring Festival in February and the distribution range and number of fishing vessels which were affected by the supplement of fishery resources in current year and the concentration of coastal feeding groups reached the peaks in the south fishing region in August and in the north fishing ground in October,respectively.Meanwhile,the tempo-spatial distribution of fishing vessels and the changes of their barycenter also indicat the influence of Yellow Sea Warm Current,Taiwan Warm Current,Coastal Current,and Changjiang Diluted Water on the distribution of fishery resources.The effects of fishery policy are well reflected in the fishing vessel data.During the closed fishing season,the sailings had obviously decreased,but fishing activities had not completely disappeared,and illegal fishing may still occur.The annual sailings in the south fishing ground decreased and the barycenter in the north or south fishing grounds generally moved westward,which might be related to the change of fishery resources.The quality of remote sensing data would be impacted by cloud cover and other factors,but SNPP/VIIRS night light remote sensing data could still provide support for the monitoring of the light-fishing industry in the coastal regions of China.(2)The results of GAM shown that year,month,longitude,latitude,SST,SSH,fleet and lunar day were the key factors affecting nominal CPUE of Chub mackerel in the East China Sea and Yellow Sea,which combined explained 16.3%of the variance in model.The spatial weighted standardized CPUE and the year effecting index from GAM both shown a fluctuating downward trend,which may be related to the environmental impact on the Chub mackerel resources.All spatial weighted standardized CPUE had similar change trend but this has a huge difference from the year effecting index from GAM.The spatial distribution of Chub mackerel resources was not uniform,so this paper proposed that the spatial weighted standardized CPUE was more reasonable.(3)Chub mackerel has an uneven distribution.If we used the year effecting index from GAM as the standardized CPUE,which would affect the quality of stock assessment of fish rescource.If the catch data could not reflect the real catch of Chub mackerel,it would affect the quality of the stock assessment of Chub mackerel in the East China Sea and Yellow Seaand overestimate the overfishing intensity.Chub mackerel had been suffering from overfished and overfishing in 2015.Total allowable catch(TAC)should be controlled below 4.59×10~5t in the future.However,the changes of marine environment would play an important role in effecting the fluctuation of Chub mackerel resources except fishing,which would make more uncertain results of this paper. |
