Environmental Effects Of Spatialtemporal Distribution Of Spawning Ground Of Major Economic Fishes In The Western Guangdong Waters,South China Sea

Environmental effects of spawning ground of major economic fishes in the WGW were analyzed,based on generalized Additive Models(GAM),Center of Gravity(Co G)of spawning sites and statistical analysis.Locations of central spawning ground and fish-egg density were predicted,based on Habitat Suitability Index(HSI).Data used in this study were the survey data of spawning grounds of major economic fishes in the western Guangdong waters(WGW)from April to July in 2014-2017 and the satellite remote sensing data of sea surface Temperature(SST),chlorophyll a concentration(Chl-a),sea surface salinity(SSS)from floats and Depth and Slope data obtained from digital elevation model(DEM)data of seabed topography.(1)The suitable marine environment of spawning ground for major economic fishes in the WGW were determined.In the northern WGW,the suitable SST for spawning ground of main economic fish in April was 22-24?,and the SSS was 33.2-33.5 PSU;the suitable SST for spawning ground in May was 24-25?,and the SSS was 33.7-33.8PSU;the suitable SST for spawning ground in June was 28-30?,and the SSS was greater than 33.9 PSU.In the southern WGW,the SST of spawning ground in April was 24-26?,SSS was 33.5-34 PSU,Chl-a was 0.1-0.15 mg/m~3;the SST of spawning ground in June was 28-31?,SSS was 33.5-33.7 PSU,Chl-a was 0.05-0.15 mg/m~3;the SST of spawning ground in July was 29-30?,SSS was 33.3-33.8 PSU,Chl-a was 0.05-0.2 mg/m~3.The suitable depth of spawning ground was 10-20 m in the northern WGW and 50-100 m in the southern WGW.There was a linear positive correlation between the fish-eggs density of spawning grounds and slope in the northern and southern WGW.The spawning ground in the southern WGW was suitable to inhabit in the sea area with longitude of 19.5-20.5°N and latitude of 111.25-111.75°E.(2)Based on GAM,the influence degree of different marine environment on spawning grounds of main economic fishes in the WGW was determined.The cumulative interpretation deviation of GAM to the fish-eggs density of spawning ground in the northern WGW was 57.2%.Among them,the most influential factor on the fish-eggs density was SSS,with a contribution rate of 32.1%;the second was SST,depth,month,Chl-a,with a contribution rate of 10.7%,8.8%,2.6%and 2.6%respectively;the least influential factor on the fish-eggs density was distance,with a contribution rate of 0.4%.The cumulative interpretation deviation of GAM to the fish-eggs density of spawning grounds in the southern WGW was 46.5%.Among them,the most influential factor on fish-eggs density was SST,with a contribution rate of 11.1%;the next was lat,lon,month,SSS,Chl-a,depth,with a contribution rate of 10.3%,9.1%,5.6%,4.8%,3%and 1.4%respectively;the least influential factor on fish-eggs density was slope,with a contribution rate of 1.2%.(3)Through the analysis of the migration of the Co G of the spawning ground,it was found that the Co G of the inshore spawning ground in WGW shifted 0.38 E eastward and0.26 N northward from spring to summer.(4)The habitat index model of spawning grounds of main economic fishes in the southern waters WGW showed that in April,the suitable SST for fish eggs ranged from24.62 to 25.02?,the optimum was 24.82?;the SSS was 32.99 to 33.19 PSU,the optimum was 33.09 PSU;the Depth was 8.55 to 9.65 m,the optimum was 9.1 m.The suitable SST for fish eggs in May was 27.96-28.31?,the optimum was 28.13?;the SSS was 34.67-36.14 PSU,the optimum was 35.40 PSU;the Depth was 11.74-13.36 m,the optimum was 12.55 m.The suitable SST for fish eggs in June was 29.25-29.50?,the optimum was 29.37?;the SSS was 33.39-34.60 PSU,the optimum was 34.00 PSU;the Depth was 15.67-24.28 m,the optimum was 19.97 m.(5)Based on HSI,the temporal and spatial distribution of spawning grounds of main economic fishes in the WGW was predicted.From April to June,the main spawning grounds of economic fish in the WGW are mainly distributed in the northwest of the study area,and the fish-eggs density in the northeast of the study area and Qiongzhou Strait was relatively low.At the same time,the moving trend of the high value region of HSI obtained by HSI model was the same as that of the actual high fish-eggs density.In addition,we found that the difference between the predicted results of the northern may and April May Qiongzhou Strait models and the actual distribution of fish-eggs density was large,which may be related to the model not selecting enough environmental factors.(6)Habitat index models of spawning grounds of major economic fishes in the northern WGW were established by using maximum model(MAXM),minimum model(MINM),arithmetic mean model(AMM)and geometric mean method(GMM),respectively.The results showed that the accuracy of HSI model established by GMM method and MINM method for the density of fish eggs in April,May and June was the highest.The accuracy rate was more than 60%and the distribution trend of HSI was similar to that of fish fish-eggs density in spawning grounds,indicating that the habitat index model constructed by GMM and MINM methods could better predict spawning grounds in the western Guangdong sea area.