Reproductive Biology And Resource Assessment Of Exopalaemon Carinicauda In The Yangzte River Estuary

Exopalaemon carincauda constitute an important part of fishery resources in Yangtze River Eastury.Resent years,ecological imbalance is confronted with many problems,due to overfishing,environment pollution etc.E.carinicauda population shave been severely affected.E.carinicauda use by bottom trawls and cage net swere investigated in 2015,Yangtze River Eastury.Studied on relationship between distribution and environmental factors,reproductive biology and resource of E.carinicauda.Aimed at enriching and updating the research of E.carinicauda in Yangtze River estuary,for the sustainable use of resources of E.carinicauda to provide reference information.1.Distribution of Exopalaemon carincauda in the Yangtze Estuary and its relationship with environmental factorsBased on the survey date of fishery resources in the Yangtze Estury in February,May,Auguest and November,2015,this paper analyzed the distribution patterns of thewhite shrimps in the Yangtze Estuary in the four seasons and the effects of water temperature,salinity,and depth on these distribution patterns.The results showed that the E.carinicauda and E.annandalei were distributed in the Yangtze river estuary during four seasons of spring,summer,autumn and winter.There were significant seasonal differences in abundance between E.carinicauda and E.annandalei,performed that autumn(November)was the highest,winter(February)was the minimum.E.carinicauda distributed mainly in northern waters,E.annandalei are mainly distributed in the waters of the south branch.E.carinicauda were distributed mainly in northern waters,E.annandalei were mainly distributed in the waters of the south branch.By analyzing between the distribution of abundance and environmental factors,show that salinity,tempreture,dissolved oxygen and pH on the distribution of E.carinicauda and E.annandalei is great.2.Reproductive Biology and resources assessment of Exopalaemon carinicauda in the Yangzte River EstuaryReproductive biology of E.carinicauda was studied during Nov 2014 through Oct 2015 in Yangtze River Estuary.The results showed that the body length of E.carinicauda ranged from 25 mm to 75 mm with an average of(48.32±9.07)mm,and dominant body length was 35~55mm.Annual variation of monthly sex ratio of E.carinicauda was in the range from 0.89 to 1.63 with an average of 1.2±0.22.There was no significant difference between male and female numbers by chi-sequare test(P>0.05).The main breeding season began in the late March and lasted until late October and the spawning peaks occurred in May and August;The reproductive population was mainly overwintering shrimp in May and June,and mainly small-medium of non-overwintering shrimp in July.The absolute fecundity(F)ranged from 660 to 8000 egg.Absolute fecundity and body length(L)were observed a positive straight line correlation as following equation: F=68.86L-2072(R2=0.498).In addition,the absolute fecundity was also linear with body weight(W),namely,F=318.5W+267.0(R2=0.504).The individual relative fecundity of body length(F/L)varied from 2.97 to 154.35 egg.mm-1,and the individual relative fecundity of body weight(F/W)varied from 107.87 to 1964.66 egg/g.The individual absolute relation fecundity(F)and the individual relative fecundity of body length(F/L)were positively correlated to these biological character indexes;The individual relative fecundity of body weight(F/W)was significantly correlated to net body weight(W0)and gonado somatic indices(GSI).The relationship between the absolute fecundity(F)and body length(L),body weight(W),net body weight(W0),and gonado somatic indices(GSI)could be described by a power function,and the relationship between the absolute fecundity(F)and ovary weight(W1)can be regressed by a liner,as well as the individual relative fecundity of body length(F/L).The individual relative fecundity of bodyweight(F/W)was power function relation with ovary weight(W1)and it is liner relation with gonado somatic indices(GSI).Multi-step wise regressive analyses show that the absolute fecundity(F)was significantly related with ovary weight(W1).3.Population Dynamics and Estimation of Sustaining Yield for Exopalaemon carinicauda in the Yangzte River EstuaryThe body length of the sample female group ranged from 27 mm to 70 mm,the dominant length group was 35 mm to 50 mm.The monthly length-frequency data of E.carinicauda obtained during 2014-2015 in the Yangtze estuary were analyzed by the FiSAT II.The result showed that the growth parameter(K)and limit length(L?)were 1.01 and 79.8 mm,while the total mortality rate(Z),the natural mortality rate(M)and the fishing mortality rate(F)were 4.81,1.94 and 2.87,respectively.Moreover,the current exploitation(E)of E.carinicaudain Yangtze estuary was 0.597 per year,which was smaller than Fopt(0.5).The Steady-state Biomass was 2.234×109ind or 463.54 t by usingLength-Structured Virtual Population Analysis.Yield-per-recruit,biomass,yield,and the value of Yield analysis indicated that E.carinicauda groups on the use of perspective.There had bigger recruitment during July and August,suggested that the introduction of fishing season in July and August.