Habitat Fingerprint Of Coilia Nasus From The Yellow Sea Based On Otolith Microchemistry Analysis

The Yellow Sea is located at the north of the East China Sea,which it bounds on a line running from the mouth of the Yangtze River to Cheju Island off South Korea.The area of the Yellow Sea proper(excluding the Bohai Sea)is about 380,000 square km;its mean depth is 44 meters,and its maximum depth is some 152 meters.Coilia nasus species is commonly distributed in every part of the western coastal waters of Korea and the Ariake Sea of south western Japan.In China the fish is distributed in near-ocean waters and freshwater rivers.It is commercially viable species due to it delicacy and nutritional value.As an anadromous species,C.nasus migrate from coastal waters to freshwater areas every year during the spawning season.The occurrence,timing and extent of movements can have a strong effect on the ecological processes of populations for migratory species.An understanding of the spatial structure of fish stocks and the connectivity within and between them is increasingly considered as an important pre-requisite for sustainable fisheries management.It is noteworthy that C.nasus in the Yangtze River might move into southern Yellow Sea for feeding and the fish was reported to be a ’typifying’ species in the region of the Yellow Sea.However,there has not been much evidence found for anadromous movement on C.nasus in the nearshore and offshore regions of the Yellow Sea.The aim of the present study was to validate the environmental signatures of Sr and Ca in the otolith of C.nasus fish from two different sites of Qidong and Dayanggang water areas in the Yellow Sea Yellow Sea;Group 1:Qidong group(QDCE),Group 2:Dayanggang group(DYCE),respectively,and determine the habitats that the C.nasus experienced using electron probe microanalysis(EPMA).Otolith microchemistry was chosen due to its ability to identify natal origin or nursery areas,classify adults to their areas of origin and also estimate population structure and discriminating stocks which satisfy the aim of determining habitat use and life history characteristic and patterns in present study.Fish samples were collected from two different sites in the Yellow Sea.The result from the life-history transect as well as X-ray intensity maps of the otoliths from the fish of these two sites analyzed in this study indicated that all samples from the QDCE showed a similar pattern.Otoliths of C.nasus from the QDCE site in the Yellow Sea showed a wider bluish central core region(low Sr:Ca ratios<3)as indicated by the life history transects as well as X-ray intensity maps of the Sr level distribution in the otoliths indicating that the fish were born in freshwater and stayed there for a longer period in that environment.Then they alternated among bluish and greenish or yellowish adjacent to the central core regions,corresponding to the migration of these species.They utilize freshwater for spawning and estuarine environments for breeding,nursery,habitat and feeding,to some extent the Yellow Sea as feeding and growth areas while all of C.nasus individuals from the DYCE showed that there were complex variability of Sr:Ca ratios.From the values of Sr:Ca ratios in the central area around the core along the life-history transects of each individual,the C.nasus in the present study could be divided into three group,i.e.group 1 had a wider bluish core had significantly wider bluish central regions.Group 2 had shorter bluish central core regions with a similar lower Sr:Ca ratios central region from the core,In contrast,group 3 had shorter greenish central core regions indicating initial estuarine resident.They also alternated among bluish and greenish or yellowish adjacent to the core regions,depicting their anadromous character.From all the two sites of the Yellow Sea,it has been revealed that C.nasus of Yellow Sea has freshwater and estuarine initial life history.The species migrate frequently between freshwater and estuarine and mostly spend some part of their life feeding in Yellow Sea.The present study provides an integrated insight of characteristics of habitat use of C.nasus from two different sites in Yellow Sea and can give very useful basic information for future effective management,conservation and sustainable utilization of this valuable fish species in these important areas.