Study On Resources Dynamics And Conservation Of Eriocheir Sinensis In The Middle And Lower Reaches Of The Yangtze River

In this thesis,Chinese mitten crab?Eriocheir sinensis?in the Yangtze River water system was taken as the research object.By adopting the multidisciplinary research method,we have mastered the resource dynamics and its changing rules of E.sinensis in the middle and lower reaches of the Yangtze River,and the Countermeasures for the protection and management of E.sinensis were put forward.The main results are as follows:1.Study on the resource dynamics and their changing rules of E.sinensis in the middle and lower reaches of the Yangtze River.?1?Resources dynamics of adult crab of E.sinensis.During the period from 2011 to2015,during the middle and lower reaches of the Yangtze River,Fishing period and flood season of crabs changed.The fishing period in the middle reaches increased by20-30 days,and the downstream fishing period decreased by 7-12 days.The density of E.sinensis in the lower reaches of the river is much higher than that in the upper reaches of the Yangtze River.The CPUE of each monitoring point in the estuaries fluctuates between 9.04 and 30.86 kg/day.The CPUE monitoring point in Anqing of the upper Changjiang region is declining year by year,from 3.09 to 30.86 kg/?day ship?in 2011to 0.66 kg/?day ship?and 0.67 kg/?day ship?in 2014 and 2015;the dominant shell width groups of the crabs in Jiangxi,Anhui,and Yangtze River estuaries were concentrated at 60⁸4mm and 50⁸4mm and 45⁷9mm respectively,accounting for82.46%and 92.96%and 95.88%of the population,respectively,it confirms the predecessor's statement that the crabs are large in size and of high quality in the upper reaches of the Yangtze River.?2?Resources dynamics of juvenile crab of E.sinensis.Juvenile crabs are found throughout the Yangtze River in the four seasons.But the time of its flood season is very seasonally strong.The number of juvenile crabs in the upper river sections of Zhenjiang and Yangzhou is small and their specifications are large.The downstream river sections of Zhenjiang and Yangzhou are numerous and small in size.In 2005 and2006,the resources of Zhenjiang young crabs gradually recovered to become eels,and fishermen began to fish.In 2008,the catch of young crabs reached the highest level of6,000kg in recent years.Since then,the catch of young crabs has declined slightly.In recent years,catches have fluctuated within the range of 3,000 to 4,000kg.Young crabs are caught from November to March of the following year.The average size of juvenile crabs is the largest during the early?November?flood season.From the peak of fishing?late December?to the late Sui?early March?,the crabs will be caught smaller and smaller.?3?Resources dynamics of megalopa of E.sinensis.At present,themegalopa of E.sinensis of the Yangtze River are mainly distributed in the estuary area below Jiangyin.The main fishing methods include fixed plugging?flooding?,single boat transfer,and net picking.In the year of crab seedlings generation?2012?,the output of single-boat transfer and net-picking fishing was the highest,and the output of different fishing methods was in the following order:net picking>river channel plugging>shoal plugging>sluice fishing;In the year of dispersal of crab seedlings?2011,2013?,the catch of megalopa was mainly fixed plug production.The output of different fishing methods was ranked as follows:river channel plugging>shallow bank plugging>transfer network>picking nets>sluice fishing.In recent years,the distribution of crab seedlings has continued to shift towards the south branch of the Yangtze estuary.During2012 and 2013,both the catch of megalopa were higher than the north branch in the southern branch,and the catch ratios of the southern and northern branches of crab increased from 4.8:1 in 2012 to 10.4:1 in 2013.2.Study on the causes of the resource change of E.sinensis in the middle and lower reaches of the Yangtze River.?1?The monitoring results of the environmental pollution of the spawning field of E.sinensis in the Yangtze River Estuary showed that in February and May 2012?the breeding season of E.sinensis?,most of the water quality of spawning ground reaches the first standard of surface water,the main pollution factors were total nitrogen,inorganic nitrogen and mercury.Except for mercury,other factors in the spawning field sediment reach the first class standard of marine sediment quality.Combined with historical data and years of measured data of this project group,it is shown that:In recent years,the total environmental quality of water and sediment in the Yangtze Estuary spawning site is better than that in the 80s of last century.Besides the aggravation of petroleum and inorganic nitrogen pollution,the pollution index and exceeding standard rate of other monitoring items showed a decreasing trend.?2?We investigated effect of 3 heavy metal ions,Cu²⁺,Cd²⁺and Zn²⁺,on the embryonic development and zoea larvae of E.sinensis.Experiment showed that Cu²⁺had the greatest toxicity on embryonic development of E.sinensis,followed by Zn²⁺and Cd²⁺,successively.The LC₅₀0 values on the embryos of E.sinensis were 1.26,4.14 and2.13 mg l^-1,respectively.As to teratogenesis,the LC₅₀0 values on the larvae were 0.26,1.43 and 0.29 mg l^-1,respectively.The toxicity of the three heavy metal ions had an obvious delayed effect on the embryonic development rate of E.sinensis.Except the treatments with 10.00mg l^-11 Cu²⁺and Cd²⁺,all other treatments did not differ significantly in the earliest membrane break time of E.sinensis.The membrane break time was generally reduced by 1d,and the latest membrane break time was delayed for1d-2d.Moreover,as the ion concentration increased,the embryonic and larval malformation rates increased as well.The embryos showed the malformations of bending,shrinkage,swelling,hyperplasia and cysts.After membrane break,the larvae first showed intensive movements,but its activity soon declined until death.?3?Through systematic analysis of the changes in the resources of E.sinensis in the Yangtze River,the main risk factors for E.sinensis on the Yangtze River are water conservancy project,lake reclamation,water pollution and overfishing.The forecast model for population dynamics of E.sinensis resources in the the Yangtze river estuary was built by using CTM?Continuous Time Markov Approach,CMT?,combining with optimization method?0.618?based on of population dynamics data of E.sinensis that collected in the Yangtze river estuary from 1970 to 2012.And a forecast on the population dynamics of E.sinensis in 2013 was made in this study.The result showed that the forecast was corresponded to the field data accurately.The result showed that the forecast was corresponded to the catch data accurately and provides a new method for the prediction of crab resources.3.Study on the genetic diversity and conservation countermeasures of E.sinensis in the middle and lower reaches of the Yangtze River.?1?We obtained mt DNA control region sequences of 102 E.sinensis individuals of 7 populations in Yangtze River system?Adults of E.sinensis in Huangmei,Poyang lake,Pengze,Wuhu and zhengjiang,juveniles of E.sinensis in zhengjiang and the Yangtze estuary,abbreviated as HM,PY,PZ,WH,ZC,ZY and SY?and analyzed their genetic diversity.The resulted showed that the complete sequences of control region was 515 bp.Total of 65 variation sites including 31 singleton polymorphic sites and 34parsimony informative polymorphic sites were defined in the 102 individuals sampled of 7 populations,in which 60 haplotypes were detected.The haplotype diversity?Hd?was found to be 0.919±0.023,nucleotide diversity 0.01007±0.00081,the average nucleotide difference?K?5.106.Genetic differentiation index?Fst?among populations was-0.0098 to 0.0983;genetic distance was between 0.0067 to 0.0122;the genetic variation among populations accounts for only 3.3%of total variation.Mismatch distribution suggested that E.sinensis in the Yangtze River system had not experienced a rapid population expansion in the recent past.The results showed that genetic diversity level of E.sinensis in the Yangtze River system was high.The seven populations had not been formed geographic differentiation obviously and panmixis would occur between them.?2?Using literature research,policy analysis and methods of research as a whole,on the basis of summarizing the experience and lessons of the development and management of E.sinensis resources,aiming at the main problems affecting the sustainable utilization of E.sinensis resources,such as water conservancy projects,lakes reclamation,water quality pollution,and cool fish traps,comprehensive application of resource ecology,resource management and other multidisciplinary theories to carry out research and analysis,five countermeasures of E.sinensis resources were proposed?That is to expand the scale of release,strengthen the protection of proliferation,and restore the natural population size of E.sinensis as soon as possible;To control the fishing intensity,implement the quota fishing system,and fully protect the resources of the crab,berried crab,young crab and crab seedlings;Strengthening the administration of fisheries,increasing cruise inspections,eliminating all kinds of harmful fishing and fishing laws,and cracking down on illegal fishing practices;Strengthening resources monitoring,scientific assessment of the flow,guiding the management and sustainable use of resources;To conduct the management of the species,to establish the standard of the Chinese fuzzy crabbing,to prevent the breeding and degradation of the species?.We also put forward policy suggestions on adhering to the principle of protecting priority,strengthening the management of water pollution,rationalizing the regulatory system,establishing the system of proliferating and discharging,and strengthening the publicity of resources protection.