Influences of environmental factors on the spawning stock-recruitment relationship of Portunus trituberculatus in the northern East China Sea

Based on the Ricker-type models,the spawning stock-recruitment(S-R)relationship of Portunus trituberculatus was analysed under the impacts of environmental factors(including red tide area(AORT),sea level height(SLH),sea surface salinity(SSS)and typhoon landing times(TYP))in the northern East China Sea in 2001 and 2014.Besides the traditional Ricker model,two other Ricker-type S-R models were built:Ricker model with ln-linear environmental impact(Ricker-type 2)and Ricker model with ln-quadratic polynomial environmental impact(Ricker-type 3).Results showed that AORT,SLH,SSS and TYP had great influences on the recruitment of P.trituberculatus.When SSS reached 29 and 31,recruitment decreased from 20.7×10^(3) million to 8.3×10^(3) million individuals.In this case,recruitment declined,whereas AORT and TYP increased.Analysis of the S-R model showed that the Akaike information criterion(AIC)value of the traditional Ricker model was 14.619,which remarkably decreased after addition of the environmental factors.Different numbers of environmental factors were added to the Ricker model,and the best result was obtained when four factors were added to the model together.Moreover,Ricker-type 2 model,with the AIC value of-5.307,was better than Ricker-type 3 model(add above four environmental factors at the same time).The findings indicated that the mechanisms by which various environmental factors affect the S-R relationship are different.