Remote Sensing Of Fishery Resources And Environment In Daya Bay And Egong Bay

Daya Bay is a typical offshore fisheries area in the coasts of South China Sea（SCS）.With superior geographical location and excellent ecological environments,Daya Bay played an important role in aquatic resources germplasm bank in Guangdong province.Deterioration ecological environment,decrease of biodiversity and poor stability of the ecosystem have occurred due to the development of industry,agriculture and aquaculture in social economy.Based on the Near-infrared spectroscopy,Sea Surface Temperature（SST）,Ocean Color（OC）,as well as the environmental data surveyed of fishery resources,the paper made the primary research about the organic carbon in marine sediments,assessment of fishery resources by remote sensing and relationship between fishery resources and environment by applying partial least squares（PLS）,Savitzky-Golay（SG）smoothing,the vertical generalized production model（VGPM）,Tait,Cushing,Nutritional dynamic model,Generalized linear model（GLM）and kriging interpolation in Daya Bay and Egong Bay.Results were summarized as follows:（1）The performance of a portable Near-infrared（NIR）spectrometer was evaluated to determine organic carbon in marine sediments.NIR spectroscopy combined with the PLS regression and SG smoothing were successfully applied to rapid and reagent-free determination of organic carbon.Using the PLS-SG model with 1 nd order derivative,2 th polynomial and 11 smoothing points,the root-mean-square errors（RMSEP_M）and correlation coefficients(R_P,M)of prediction for modeling were 0.073%and0.894,respectively,the root-mean-square errors（RMSEP_V）and correlation coefficients(R_P,V)of prediction for validation were 0.075%and 0.883,respectively.Results showed that the small portable NIR instrument achieved well prediction effect for the analysis of organic carbon in marine sediments,which had advantages of rapid,easy to carry and operate suitable for large-scale applications to analyze marine sediments.（2）PP and fishery resources in Daya Bay were assessed through remote sensing.There was a distinctive seasonal feature that PP in summer reached highest（average of 1595.60 mg C/m²d）,the autumn ranked secondly（1274.67 mg C/m²d）,PP in spring is slightly higher than that in winter,remained flat basically in Daya Bay.The spatial distribution trend was decreasing from nearshore to offshore and outside the bay gradually,with the PP more than 1000 mg C/m²d by nearshore and ranging of 800-1000 mg C/m²d outside the bay.Chl-a is one of the most marine environmental factors affecting the PP in Daya Bay,where their spatial and temporal characteristics distributed similarly.Cushing model obtained the optimum effect with the actual survey fishery data,in terms of evaluating the seasonal variations of potential fishery product in Daya Bay.（3）Seasonal variations of fishery resources in Egong Bay was analyzed.Results showed that there were 113 species of fishery resources,belonged to78 genus,50 families,14 orders and 3 classes,in this area.The species number was the highest in summer（61 species）and was the minimum in autumn（53 species）.The stock density and tail stock density of fishery resources were the minimum in summer（5950.20 kg/km² and 356.45individual/km²,respectively）.The percentage of fish stock density and tail stock density were the highest in summer（51.99%and 42.19%）.High values of SCPUE occurred in spring and autumn,reaching 5.65 and 5.33,respectively.SCPUE was generally low in summer,ranging between 0.52-0.96.The seasonal variations of size spectra indicated that fishing intensity was the biggest in autumn,and was the least in summer.Additionally,biodiversity index presented the highest in summer and lowest in winter,including Shannon-Wiener diversity index,Margalef richness index and Pielou evenness index,with the same trend as summer>spring>autumn>winter.The study evaluated the status of fishery resources and the environment,explored the cause of seasonal variation of fishery resources by remote sensing and NIR spectroscopy technology in Daya Bay and Egong Bay.Results of this study could provide scientific basis for assessment and management of fishery resources in typical offshore fisheries area in the SCS.