Spatiotemporal Dynamics Of Anchovy Population And Its Response To Environmental Factors In The Yellow Sea Based On Ocean RS And GIS

Marine is the foundation of human survival and development, as an important part ofmarine ecosystem, fish plays a significant role in ensuring food security and provides a largeamount of high-quality protein for human being. With the increasing of fishing effort andeffects of climate change, marine fishery resource has been seriously damaged. As an react tothe effects of anthropogenic activities and climate changes on marine living resources andenvironmet, international organizations have launched a series of global ocean researchprogram, the response of marine fishery resources to global change and human activities is animportant part of the ongoing IMBER plan now. In the present study, under the doubleinfluences of fishing pressure and climate change, spatioemporal dynamics of anchovy(Engraulis japonicus)population and its relationship with environmental factors in theYellow Sea were analyzed. The data for this study were fom the1986-2010bottom trawl datain the Yellow Sea and related marine environmental data obtained by remote sensing. Thisstudy will be of great significance to explore how China coastal ecosystems respond toclimate changes and human activities, and also offer a scientific evidence for fisherymanagement and resource conservation in the Yellow Sea. On the basis of marineenvironmental factors being analyzed by remote sensing in the Yellow Sea, this paper mainlystudied the following several aspects.First, seasonal and interannual changes in the relative stock density of anchovy in theYellow Sea were analyzed. As for seasonal changes, the lowest value of the relative stockdensity appeared in autumn, and the highest value appeared in winter in most years, thefrequency of occurrence was the highest in winter and lowest in autumn in most years, andboth the relative stock density and frequency of occurrence changed minimally from spring tosummer. As for interannual variations, the relative stock density of anchovy declined in allseasons after1986, and the decrease was the smallest in summer, but the interannual variationin frequency of occurrence was relative small, which had a slight drop in winter and spring,and an upward trend in summer and autumn.Second, seasonal and interannual variations in spatial distribution of anchovy in the Yellow Sea were studied thoroughly. On the basis of qualitative analysis using resourceabundance maps, the interannual variations in centralized distribution regions of theanchovy's capture locations and stock density were quantitatively studied using borderhistogram. And combining with spatial statistic and geostatistic technique of GIS, with themethod of trend surface analysis, hot analysis and standard deviational ellipse, seasonal andinterannual changes in spatial distribution were clarified comprehensively and in multi-angle,and the migration trend of anchovy was analyzed by the change of stock density center. Thespatial distribution changed obviously in different seasons. The stock density of anchovydropped gradually from the eastern deep waters to the shore in winter, but in spring whichwas contrary to the winter trend and decreased gradually from the shore to the deep waters,and in summer which dropped from the north to the south with the high stock densityscattered, in autumn which was similarity to the winter and decreased from the deep waters tothe shore. About spatial distribution, anchovy moved northward in spring, summer andautumn, and there was not obvious change trend in winter from1986to2010. The anchovy'scapture locatons mainly distributed between123.5°E and124°E in longitudinal direction indifferent years and different seasons, but the centralized distribution regions of anchovy'sstock density had not apparent trend.Third, spatial distribution characteristics of anchovy were analyzed using exploratoryspatial data analysis (ESDA) method, and combining with GIS, we had a further study ofspatial distribution configuration by moran scattered maps. Anchovy was located with spatialcluster in most years, but the degree of centralization was different. And the spatialdistribution configuriation of anchovy had apparent interannual variations. The relatilve stockdensity of anchovy had a trend of "high in north and low in south" in spring, but there was alarger interannual change in the proportion of station numbers of high-high type and low-lowtype. The station numbers of high-high type had an interannual increase in summer, and thehigh-high type regions moved northward in autumn. In winter, the high-high type regionscentralized in the eastern deep waters, but the low-low type regions was distributed in theshore shallow waters and the north of studied area, and neither of them had significantinterannual change.Fourth, the relationship between anchovy's distribution and sea surface temperature(SST), chlorophyll concentration was studied. The result indicated that the anchovy wasdistributed between different suitable temperature range in different seasons, the relationshipbetween anchovy's distribution and SST was most significant and mainly located on theright of warm tongue of the Yellow Sea Warm Current in January. Despite the chlorophyll concentration value was mixed with other information such as sediment, there was a closerelation between anchovy distribution and chlorophyll concentration in winter and spring.After qualitative analysis, the relationship between marine environmental factors and catchper unit effort (CPUE), presence/absence (P/A) of anchovy of all seasons were exploredquantitatively using generalized additive models (GAMs), in order to distinguish the impactof environmental factors on the stock density and geographical distribution of anchovy, andreveal the differences of the influence in different seasons. The relationship between marineenvironmental factors and CPUE of anchovy indicated that the netting time had a greaterimpact on the CPUE in all four seasons, but the affecting way was different in differentseasons. The water depth had impacts of different degree on the CPUE except in autumn.The influence of SST on CPUE was significant in winter, the summer and autumn followedby, and there was no correlation in spring. The influence of chlorophyll concentration onCPUE was significant in spring, the winter followed by, and there was no correlation insummer and autumn. The sea surface temperature gradient (TGR) affected the CPUE only inwinter.The relationship between marine environmental factors and P/A of anchovy showed thatthe netting time had significant influence on the P/A except in summer, but the influencingtrend was different from the CPUE. It was obvious of the impact of water depth on the P/Ain spring and summer, and the influencing trend was the same to the CPUE. SST in winterand summer, chlorophyll concentration in spring and winter, and TGR in winter were allrelated to the P/A significantly, and which influenced the P/A of anchovy on great degree.Fifth, by way of anchovy's suitable temperature being as the characteristic temperature,we studied the relationship between interannual variations in spatial distribution, spatialconfiguration of wintering anchovy and SST obtained by remote sensing. The resultsuggested that the variations in water temperature had effects on the latitudinal distributionof the wintering anchovy, and whether the anchovy distributed shoreward or not wasdetermined by the interannual variations of the Yellow Sea Warm Current. And the high-hightype centralized regions of wintering anchovy's stock density in the latitudinal distributionwas affected by the variations in water temperature.