The Distributional Features Of The Spawning Ground Of Eriocheir Sinensis And Correlation To Major Environmental Factors In Yangtze River Estuary

In this paper, the Chinese mitten crab (Eriocheir sinensis) in Yangtze River estuarywas studied. The temporal and spatial distributional features of the mature crab andspawning crab of Eriocheir sinensis in2013and features of embryonic developmentwere analyzed. Yield and resources distribution of Eriocheir sinensis megalopa between2012and2013were compared. Also, Dominant species in fishing season and the purityof Eriocheir sinensis megalopa were studied. The major environmental factors affectingthe distribution of spawning ground of Eriocheir sinensis were compared so that we caninitially speculated the range of spawning crab of Eriocheir sinensis. We study theEriocheir sinensis in Yangtze estuary to provide theoretical references for resourceassessment and protection of the Eriocheir sinensis as well as value-added relerased anddelineation of protected areas.1. Temporal and spatial distributional features of spawning crab of Eriocheirsinensis and Embryonic developmentThe mature crab and spawning crab of Eriocheir sinensis were monitored in theperiod of spawning migration of Eriocheir sinensis in Yangtze River estuary fromMarch to May. The temporal and spatial distributional features of the mature crab andspawning crab of Eriocheir sinensis in2013and features of embryonic developmentwere analyzed. The result shows that the mature crab mainly perched on the north partof Tongsha(Z10) and the central areas of Northeast of Jiuduansha(Z11、Z22) fromMarch to May, the scope of which was122°11′E,31°25′N~122°11′E,31°11′N; it rarelyperched in the center between Jiuduansha and Zhongjun shoal(Z2、Z4、Z7). Abundanceof Eriocheir sinensis spawning crab showed that the spawning crab mainly perched onthe north part of Tongsha(Z10) and the Northeast of central areas of Jiuduansha(Z11、Z22) in later March; the spawning crab mainly perched on the central areas of Northeastof Jiuduansha(Z22) and Luchao port of Pudong in later April; the spawning crab only perched on the central areas of Northeast of Jiuduansha(Z11、Z22) in later May. These3investigations showed the spawning crab of Eriocheir sinensis has no significant change.Only a little spawning crab perched on the areas between the north part of Tongsha andSouth part of Jiuduansha. The embryonic development of wild Eriocheir sinensisshowed it needed487.73D℃from cleavage stage to hatching age and535.43D℃from original zoea to hatching age. It provides theoretical references for indicating thefishing season of Eriocheir sinensis megalopa by the water temperature from March toMay.2. Preliminary assessment of Habitat Suitability of Eriocheir sinensis spawningcrab in Yangtze River estuaryThe correlation between hydrological environmental factors and spatialdistribution of Eriocheir sinensis spawning crab in Yangtze River estuary was studiedby habitat suitability model. The results showed that the main habitat conditions forspawning crabs were: salinity9~15, flowing rate of water1.3~1.5m·s-1, depth3~7m,transparency10~23cm, the suitability of which is greater than o.6. Distribution ofHabitat Suitability Index(HSI) showed that the Z6、Z7、Z11、Z22、Z23which belongsto areas of North port and Jiuduansha of Yangtze River estuary has greater HSI, whichis greater than0.5. The HSI of Z6is0.6692, which is greatest than any others. Wespeculated initially that main suitable distribution was20n mile east of Hengsha and5n mile downstream of Jiuduansha and the distribution of spawning ground for Eriocheirsinensis was121°58’ to122°12′East longitude and31°05′to31°22′North latitude.Compared with1980s, the area of spawning ground of Eriocheir sinensis was decreased.At the same time, it moved5.14n mile to the south of Yangtze River estuary. The resultcan provide theoretical references for protection of the Eriocheir sinensis and scientificbasis for delineation of spawning ground of Eriocheir sinensis.3. Temporal and spatial distributional features of Eriocheir sinensis megalopaThe Monitor of Eriocheir sinensis megalopa in Beibaxiao, Dongwangsha,Tuanjiesha, Xijiagang, Xinmingang, Waigaoqiao and Sanjiagang was analysised in theperiod of fishing season in2013. The amount of fishing between2013and2012wascompared. The temporal and spatial distributional features and dominant species and thepurity of Eriocheir sinensis megalopa were studied. The result shows that it appearedearlier and had larger amount in north branch of Chongmin than south branch. Theproportion of north branch was91.84%. In time scale, the fishing season in2013was from1stjune to11thjune. The amount pecked at4thto6thwhich is larger than1500kg.In the spatial scale, the proportion of Sanjiagang was52.53%; the proportion ofTuanjiesha was31.62%; the proportion of Dongwangsha was8.76%; the summary ofthese three stations was92.91%. Among the rest four stations, the proportion ofBeibaxiao was0. The total of fishing for Eriocheir sinensis megalopa in2103was6027.2kg which was decreased71.6%compared with2012. The proportion of2013between south branch and north branch was10.4:1, which of2012was4.8:1. The studyof dominant species and the purity showed that, the purity of Eriocheir sinensismegalopa gradually increased with the time. The peak of purity was consistent with thepeak of fishing. The purity of the station which was nearer with the outer estuary got thepeak first. Four kinds of megalopa were found at the end of fishing season. Theproportion of Tientsinensis Helice megalopa is the greatest than any others besideEriocheir sinensis megalopa. The result can provide theoretical references for protectionof the Eriocheir sinensis sustainable utilization.