The Dynamics Of The Neon Flying Squid Resource Under Climate Change Scenarios In The Northwest Pacific Ocean

As one of the most important economic species in the Northwest Pacific Ocean,the Neon flying squid(Ommastrephes bartramii)plays an important role in the North Pacific ecosystem,and has been included in the management of the North Pacific Fisheries Commission(NPFC).The abundance of O.bartramii fluctuates violently during the years,affected by the environment and climate change in every life history stage.The influence of global climate change and local marine environmental changes on the abundance and distribution of O.bartramii is rather striking,as O.bartramii is a short-life-cycle species and usually lives no more than one year.In the past 20 years,important progress has been made in the near real time prediction of the abundance and distribution of O.bartramii.However,the long-term(to the end of the 21 st century)prediction of O.bartramii resource and fishing ground under the climate change scenarios remains meager.Therefore,the resource change of O.bartramii in the Northwest Pacific under the future climate change scenario is studied in this paper,combined with the latest progress of climate change research.The scientific hypothesis of this paper is: under the background of future climate change,the marine biophysical and chemical environment will change,which will lead to the changes in the temporal and spatial distribution of potential habitat,fishing season and recruitment of O.bartramii resource.The distribution of potential habitat of O.bartramii under different climate change scenarios in the future is analyzed using the projection climate data,which is the results of the fifth report of IPCC in September 2013,i.e.Coupled Model Inter-comparison Project phase 5(CMIP5).Furthermore,the change of fishing season is also analyzed through the quantitative analysis of habitat area and the recruitment of O.bartramii resource is estimated according to the environment of spawning and feeding ground.This paper also puts some advises of fishery management of O.bartramii.The main results are as follows:(1)The application of maximum entropy model(Max Ent)in the simulation of habitat distribution of O.bartramii.The monthly potential habitat distribution of O.bartramii in the Northwest Pacific Ocean during major fishing months(from July to October)were explored using Max Ent fitted with fishery data of Chinese commercial squid-jigging vessels and five oceanographic environmental factors derived from remote sensing data,which is the sea surface temperature(SST),the concentration of Chlorophyll-a(Chl-a),the net primary productivity(NPP),the mixed layer depth(MLD),and the sea level anomaly(SLA).Furthermore,the modeled habitat was evaluated using Arc GIS software.The most suitable habitat of O.bartramii are mainly located in 39°N-43°N,150°E-163°E in July and moves eastward in August.The fairy suitable habitat also expands northward to 46°N in August.The most and fairly suitable habitat shrinks westward in September,mainly located in 40°N-46°N and 150°E-160°E.In October the potential habitats moves southward,mainly located in 40°N-45°N and 150°E-165°E.The most influential factors of the potential habitats vary during July to October,which is SST in July and August,MLD and SST in September,and NPP and SST in October.Results show that the temporal and spatial distribution of potential habitats of O.bartramii is affected by environmental factors and vary explicitly during July to October.Also the Max Ent model has high accuracy in simulating the potential O.bartramii distribution in the Northwest Pacific Ocean.(2)Based on the sea surface temperature,which is the most dominant environmental climate factor affecting the distribution of O.bartramii,the potential habitat changes of O.bartramii in July-October in 1996-2005,2021-2030,2051-2060 and 2090-2100 were analyzed using maximum entropymodel with the historical climate data from 1996 to 2005 and the projection climate data from RCP4.5 and RCP8.5 scenarios.The results show that the fishing grounds of O.bartramii performs a seasonal north-south migration.With the feature climate change the potential habitat distribution of O.bartramii between July and October in 2021-2030,2051-2060 and 2090-2100 will move northward and the suitable habitat area will increase compare to 1996-2005 under both scenarios of RCP4.5 and RCP8.0.The seasonal north-south migration of O.bartramii may be affected by the suitable SST range in fishing season.Under scenario of RCP 4.5,the potential most suitable habitat for O.bartramii will move northward by 1-2°and the suitable habitat area will increase by 3-13% by the end of the 21 st century.Under scenario of RCP 8.5,the potential most suitable habitat for O.bartramii will move northward by 3-5°and the suitable habitat area will increase by 42%-80% by the end of the 21 st century.(3)The influence of the environmental factors on the potential habitat and the fishing season.Combined with multiple environmental and climatic factors affecting the distribution of O.bartramii,including SST,SSS,sea surface height above the geoid(SSHAG),primary organic carbon production(POCP)of all phytoplankton,a habitat model is established using Max Ent.The temporal and spatial changes of potential habitat of O.bartramii in fishing season(July to November)in 2000,2025,2055 and 2095 are analyzed and quantified to further explore the possible changes of fishing season of O.bartramii using the historical data of environmental and climatic factors in 1996-2005 and the predicted climate factors in the scenarios of RCP4.5 and RCP8.5.The result shows that O.bartramii habitat moved to the North Pole under climate change.The habitat moves to the North Pole significantly between August and October in 2025,2055 and 2095 under the RCP4.5 scenario and moves to the North Pole significantly between July and October in 2025,2055 and 2095 under the RCP8.5 scenario.Moreover,the potential suitable habitat area of O.bartramii decreased.By 2095 of the RCP4.5 scenario it almost disappeared between July and September,and decreased by 23% in October and 43% in November.By 2095 of the RCP8.5 scenario it almost disappeared between July and November,except October,which increased by 34%.These results indicate that the fishing ground of O.bartramii will move northward and fishing season will delayed and the total fishing operation time may be shortened in the future.(4)Prediction of the future recruitment of O.bartramii resources.Based on the previous research,the spawning ground of O.bartramii is divided into empirical spawning ground and speculated spawning ground.By analyzing the correlation between the proportions of the appropriate water temperature area in the total area(Ps)in the empirical spawning ground,speculated spawning ground and feeding ground and the CPUE each month,a linear prediction model is established by selecting the month with significant statistical relationship between Ps and CPUE including the two scenarios of RCP4.5 and RCP8.5.The recruitments of O.bartramii resources are predicted using this model and the Ps of the statistical significant months in 2000,2025,2055 and 2095.The results shows that the suitable SST range of the empirical spawning ground of O.bartramii moves northward under the climate change scenario,and reaches the northernmost edge of the empirical spawning ground in 2095.The average Ps of the empirical spawning ground between January and April decreases,but the change is not significant.The suitable SST range of the speculated spawning ground also moves northward,reaching the northernmost edge of the speculated spawning ground in 2095,which is beyond the range of speculated spawning ground.The average Ps of the speculated spawning ground between January and April decreases,and the change is significant.The suitable SST range of the feeding ground moves northward and tends to expand.The average Ps of the feeding groundbetween July and October shows a downward trend with a significant change.The result of correlation analysis shows that there is a significant positive correlation between Ps and CPUE of speculated spawning ground in February and March.In the future,the CPUE of O.bartramii will decline.By 2025,the CPUE of O.bartramii will be 208.87±5.46 ton per vessel.By 2055,it will be 198±47.92 ton per vessel.By 2095,it will be 154.35±48.72 ton per vessel.Decline of O.bartramii resources will be 60.08% in 2095 compared with 2000.(5)The conservation and management mode of O.bartramii fishery to adapt to and mitigate the impact of climate change.By analyzing the mechanism and approach of the impact of climate change on O.bartramii,this paper discusses the approach and method of adaptation and mitigation of climate change in O.bartramii fishery,and finally gives suggestions for sustainable development of O.bartramii fishery that compatible with climate change under the maintenance and management mode and framework of NPFC.The suggestions include strengthening the assessment of O.bartramii fishery resources,improving the prediction ability of O.bartramii fishery resources,reducing unnecessary and ineffective fishing effort,reducing and improve fishing vessels,reducing energy consumption,improving efficiency,adjusting industrial structure,optimizing market allocation,developing fisheries management measures and early warning system to adapt to climate change.Furthermore,appropriate closed season should be set up to cope with global warming,and banned fishing areas need to set appropriate to protect the migration of O.bartramii spawns and larvae and juveniles.