Study On The Relationship Between The Catch Fluctuation Of Portunus Trituberculatus And The Human Disturbance And Environment Factors In Zhejiang Fishery

Portunus trituberculatus is the most important marine crab in Zhejiang fishery.It has a very important position in marine fishing operations in Zhejiang Province.The highest annual output has reached 20×104 tons.However,according to the statistics of the production of the three-spotted crab in Zhejiang Province and the life practice of fishermen’s fishing operations,it is found that there is a significant annual fluctuation in the production of the crabs in Zhejiang Province(the yield is large and small).It is an important scientific issue to explore the annual fluctuations of the production of Portunus trituberculatus and its influencing factors,and to establish a mathematical model between the annual fluctuations of production and environmental factors.This study collects and analyzes the fishing power data(Power)of the catching crabs of Zhejiang Province in 1980-2016,the temperature of Zhoushan City,the rainfall,the surface temperature of the East China Sea(SST),the Tropical Cyclone Disaster Index(TCI),and the El Nino Index(ONI)and Yangtze River runoff data,using Kolmogorov-Smirnov test(K-S test),general additive model(GAM)analysis and statistical analysis methods,The types of each factor data,the significant relationship between each factor and the catching yield of Portunus trituberculatus were studied,and the intrinsic relationship between the fluctuation of the yield of the crab and the related factors was analyzed.The results show:(1)K-S test showed that the data of the other factors were in line with the standard normal distribution(P>0.05),except that the time series data of the fishing pressure data did not meet the standard normal distribution(P<0.05).(2)According to the GAM model analysis of different factors and the production of Portunus trituberculatus,when the fishing pressure(Power)is greater than 250×104KW,the spring average temperature(CT)is between 15.0 and 15.7℃,and the average winter temperature(DT)is greater than 7℃,spring rainfall(MX)over 1250ml,summer rainfall(TX)less than 1500ml,spring sea surface temperature(CSST)greater than 20.5℃,typhoon disaster index(TCI)greater than 8x105,and Yangtze runoff(Runoff)less than 8x The yield(Y)is greatly affected when the 10.3 billion m3 and the El Nino index(ONI)are less than 0.3 and greater than 1.2.Among them,the fishing pressure,the one-year spring average temperature(CT1),the three-year spring sea surface temperature(CSST3),and the three-year Yangtze River flow(Runoff3)and the three-spotted crab production are significant.Correlation(P<0.05),and the models fitted with these four factors were better,and the results were more reliable.The contribution rate of each factor to the model is from high to low,the fishing pressure is 14.45,the spring average temperature is 5.96,the spring sea surface temperature is 3.09,and the Yangtze River flow is 1.97.The optimal simplified model between the final yield Y and each factor is:Log(Y)=s<Power)+s(CSST3)+s(CT1)+s(Runoff3)+ε(3)There is a clear internal relationship between production fluctuations and various related factors.First,the output generally rises with the increase of fishing pressure,and the annual increase and decrease of fishing pressure plays a key role in the annual fluctuation of production.Second,the average temperature in spring and the annual fluctuation of sea surface temperature and output in spring.There is a positive correlation between a good lead time with a time lag of 1 year.The increase of average temperature and sea surface temperature in spring can promote the recovery of fishery resources of the swimming crab.Third,the annual fluctuation of runoff and output of the Yangtze River There is a good negative correlation between the lead time and the distance of 3 years.Although the Yangtze River runoff brings a lot of nutrient salts,the continuous large amount of runoff has a great influence on the salinity of the offshore,which is not conducive to the growth of the larvae of the crab.Its resource recovery has an adverse impact.Although this study has obtained certain results,it is not deep enough at the research level.In the future research,it is necessary to combine various factors to further study the effects of various factors on the growth,development and reproduction of Portunus trituberculatus.Through quantitative data research,a more accurate dynamic prediction of the production of Portunus trituberculatus is established.The equation provides a scientific basis for the utilization and protection of the fishery resources of the swimming crab.