| Neon flying squid(Ommastrphes bartramii)is one of the most important economic fish species in the North Pacific Ocean.The western winter-spring cohort is the mainly target species caught by Chinese jigging vessels and it distributed in the west of North Pacific Ocean.The resources of squid bring the great economic and social benefits to our country.In recent years the abundance of neon flying squid fluctuate sharply,which often lead to the investment of catch effort surplus and bring the difficulty in fisheries production and management.At present,it is difficult to predict the spatial distribution and resource changes in squid.Further study the spatial-temporal of fishing ground and the prediction of resources abundance,accurately known the annual law of transformation is the important factors to realize reasonable production input and scientific management and sustainable utilization of squid resources.The scientific hypothesis of this research are,(1)squid is a highly migratory species.The life history of squid is experiencing in spawning migration and feeding migration,which has a long time span and wide distribution.Therefore,the squid migration follows a fixed migration path and changes in the migration path due to the changes in the oceanic environment.(2)squid is a short life-span species,with the characteristics of “be dead immediately after spawning”,and the stock size entirely depends on the recruitment,while the recruitment mainly depends on its mortality in the early life stage,and environmental changes have an important influence on the early life history which is from spawning to hatching and embryonic development to grow to be larvae.Therefore,the environmental factors of spawning grounds and feeding grounds have important influence on their resource supplementation.In this paper based on the data of Chinese mainland squid fishery and environment of squid fishing ground including Sea Surface Temperature(SST),Chlorophyll-a concentration(Chl-a),Sea Surface Salinity(SSS),Kuroshio current,to analyze the relationship between the change of squid fishing ground on temporal and spatial,the change of migration gravity and oceanic environment.Using the standardization catch per unit fishing effort as the squid resource abundance index,and combine the proportion of favourableSST in spawning and feeding grounds to analyze the relationship between the abundance of squid and the environmental factors of spawning grounds and feeding grounds and establishment of forecasting model for forecasting resource supplement and fishery management providing more accurate basis.(1)Using the correlation coefficient and the grey relational evaluation method based on entropy weight method,to analyze the temporal and spatial distribution of squid resource and fishing ground.The results show that there have significant difference between the sea area west of 160 ° E and the sea area east of 160 ° E.Mainly fishing grounds are distribution in the sea area of 150°E~159°E,and production accounts for about 79%~97% of the total catch in each year.From the point of latitude,sea area west of 160°E,fishing ground are mainly distributed in 40 ° N ~ 44 ° N,its production accounted for about 74.12%~ 99.61% of the total catch,and sea area east of 160°E,fishing ground are mainly distributed in 39°N~40°N,its production accounted for about 94.81%~99.85%of the total catch.Correlation coefficient analysis show that: in sea area west of 160°E,it is almost the same that spatial distribution pattern of catch in each year,and that is no significant change in the area of fishing grounds and the proportion of catch.In sea area east of 160°E,it is significant different that spatial distribution pattern of catch in each year.The results of grey relational evaluation shows that: in the sea area west of 160°E,the order of squid's abundance is: in 2004,2007,2005 and 2011 the resources of squid is the best,and in 2008,2015,2012 and 2013 the resources of squid is the better,and in 2010,2006,2014 and 2009 the resources of squid is worst.In the sea area east of 160°E,the order of abundance of squid is: in 2004,2007,2005 and 2014 the resources of squid is the best,and in 2015,2011,2013 and 2003 the resources of squid is the better,and in 2008,2009,2010 and 2012 the resources of squid is worst.(2)The relationship between interannual variability of migratory pathways and marine environment.The results showed that the proportion of production of the migratory gravity of the squid is significant negatively correlated with the dispersion degree in October and November.There is a significant positive correlation between the change of the migratory gravity in the latitude and the TNI,which does not appear in the longitude.The model of predicting the spatio-temporal variation of the migratory path of the squid has established by using the neural network combined with sea surface temperature,salinity and Chlorophyll concentration.The results of forecasting showed that during August to November,the migration gravity of squid shows the change trend of south-north-south in the latitude,and the change trend of west-east-west in the longitude.In the August and September,the estimated proportion of production of the migratory gravity area was 64% and 68% respectively.In the October and November,the prediction accuracy rate has obviously improved,and the estimated proportion of production of the migratory gravity area was 83% and 89% respectively(3)In different oceanic environment modes,the impact of different spatial resolution on the standardization of CPUE.In different oceanic environment modes,the variables that have important influence on the standardization of CPUE are significant.In the sea area west of 160°E is year,latitude,SST,and the interaction year and latitude,month and latitude respectively;In the sea area east of 160°E is latitude,the interaction year and latitude,month and latitude respectively.Under the same oceanic environment mode,the different spatial scales are most suitable for the GAM model is different from the CPUE standardization results,based on the mean square error selection 0.5°x0.5° and 1°x1° respectively as the optimal spatial scale of sea area east and west of 160°E,for CPUE standardization.Therefore,the differences in the standardization of the CPUE that result from the different modes of the oceanic environment and the different spatial scales need to be take into account when standardizing the commercial catches of the North Pacific Ocean.(4)The prediction of the squid resources based on the environmental factors of the spawning grounds and the feeding grounds.The results show that the final dividing scheme of the spawning grounds is 5°x5°,and the feeding grounds is more appropriate for the 2.5°x4°.The range of sea area screened by random forest was in agreement with that of correlation analysis,and the ability of random forest to identify potential sea areas with characteristic relationship with CPUE was excellent.The prediction results of the prediction model show that the predicted accuracy of the model is up to 90%,the sea area selected by the random forest is superior to the correlation analysis and the prediction accuracy is higher.Compared with the spawning grounds and feeding grounds,the model based on the spawning grounds is more accurate and stable. |
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