Study On Age, Growth, Reproduction And Feeding Habit Of Common Carp, Cyprinus Carpio, In Dianchi Lake

Common carp is the introduced species, but at present is the most important fishery species in Dianchi Lake. According to those 607 specimens of common carp(Cyprinus carpio) colleted in Dianchi Lake from March 2013 to June 2014, this research will analyze the characteristics of age, growth, food habits and reproduction of common carp,The main objective of the study is to provide scientific information for local fisheries management and fishery regulation based on the ecosystem. The main results are as follows:This present paper described the morphology and annulus characteristics of four calcified structures(lapillus, scale, pectoral fin and operculum), and discussed the consistency of age interpretations for common carp, Cyprinus carpio in Dianchi Lake of Yunnan province, China. Among the four structures, the sectioned lapillus showed the highest percentage of agreement values(86.2%) between two times age reading by the same reader, followed by scale(84.1%)、pectoral fin(73.7%) and operculum(72.1%);Meanwhile the average percent error of the two materials(the sectioned lapillus and scales) showed the low level, were 2.6% and 2.9%, respectively. Relative to the sectioned lapillus, the agreement was 77.5% for scales, 61.9% for operculum, 56.2% for pectoral fins; The scales were fit for aging those individuals less than 4 years old, the coefficient of variation(6.14%) was lowest; The first annuli of operculum and pectoral fins were both difficultly confirmed, the coefficient of variation of the two materials both be over12%. In short, the sectioned lapillus was the best age determination materials, while scales could be used for age determination of young individuals. But operculum and pectoral fins could not be used for determininging age of common carp in Dianchi Lake.According to the monthly marginal increment ratio of the otoliths, The results showed that annuli of otoliths formed from January to May once a year. The estimated ages of common carp group in Dianchi Lake ranged from 1 to 5 years, and the 2 age individualsaccounted for 35.95% of the total, the dominant age group of female(40.94%) and male(48.47%) are 3 age and 2age, respectively.The standard length-body weight relationships between females and males showed an allometric growth, it could be described as W=0.0524×SL2.794 for females,W=0.0524×SL2.794 for females. The von Bertalanffy growth equations were: Lt=81.9(1-e-0.1430(t+0.8115)),Wt=11639.5(1-e-0.1430(t+0.8115))2.79(Females); Lt=74.9(1-e-0.1476(t+0.8721)), Wt=8421.1(1-e-0.1476(t+0.8721))2.75(Males).The growth inflexion points were 5.9 years for females and 5.3 years for males,respectively, and the corresponding standard lengths and body weights were 49.9 cm and2909.5g for females and 43.9cm and 1941.6g for males, respectively. Comparing with common carp group in other water body,the common carp in Dianchi Lake grew more slowly as low water temperature、high fishing intensity and lack of bait biological.The total sex ratio(female:male) was 0.97:1,which was variable with the standard length. 8-32 cm in standard length were male individuals dominated,while more female in sizes larger than 32 cm. The standard length at 50% maturity(L50) were 25.8cm for female and 17.5cm for male, respectively. The first ages at maturity were 1year for male and 2years of female, respectively. According to the changes of annual gonadosomatic index,the main spawning season were in May to July. For individuals with standard length between 28.5-44.8cm and weight between 652.1-2090.8g, the absolute fecundity ranged from 48847-251460 eggs, the average absolute fecundity(with±SD) were 126983±42578eggs; the relative fecundity per unit of body weight ranged from 60.7-143.5 eggs/g and the mean was 102.2±22.4eggs/g. The relationship between absolute fecundity and standard length was described as F = 28.2× SL2.3441(R2=0.514,n=42), and relationship between absolute fecundity and body weight was F = 97.82×GW+5588.7(R2=0.562,n=42).Phytoplankton and zooplankton were the main food for common carp in Dianchi Lake, the highest relative importance index(IRI%) belonged to Daphnia, followed by Pseudoanabaena(IRI%=17.4%), Microcystis(IRI%=10.5%)and Cyclotella(IRI%=10.4%) in order. Common carp in Dianchi Lake was a generalized food fish with high diet overlapwithin individuals. The feeding diversity(H) and evenness(J) were similar with fish size and sex, but different with season, the food overlap index of Spring and winter, summer and autumn, autumn and winter were slightly higher than 0.6, and the food overlap index of spring and summer(0.26) were lowest.