Assessment Of Habitat Suitability Of Eriocheir Sinensis

In this paper,Eriocheir sinensis was selected as the research object to investigate the population distribution,growth status and main habitat of Eriocheir sinensis in Langshansha and Xinkaisha of the lower reaches of Yangze River.Main biological characteristics,relative growth rate of shell width and body weight,and the growth characteristics were investigated.The community structural characteristics of the fishery biome in the habitat of Eriocheir sinensis were investigated,including the species composition and ecological types of catch species,dominant species,diversity index and spatial-temporal contrast of community structure.The suitability of habitat for Eriocheir sinensis was preliminarily evaluated.It is hoped that it can provide a scientific basis for germplasm resources and ecological environment protection of Eriocheir sinensis in the middle and lower reaches of the Yangtze River.1.Population Characteristics of Eriocheir sinensis in Langshansha and XinkaishaFrom June 2016 to May 2017,the distribution of Eriocheir sinensis was investigated and monitored in the Langshansha and Xinkaisha of the Yangtze River.The main biological and growth characteristics of Eriocheir sinensis were studied.The results showed that the shell length of Eriocheir sinensis ranged from 4.39 mm to 66.69 mm,the shell width varied from 5.14 mm to 74.46 mm,the body weight ranged from 0.04 g to 168.72 g,the average shell length was 24.79±9.35 mm,The mean value of shell width was 27.16±10.15 mm and the average weight was 12.61±14.97 g.The dominant shell width was 0-40 mm,accounting for 93.82% of the total,and the dominant weight was 0-20 g,accounting for 81.23% of the total.The relative weight gain rate and the relative growth rate decreased with the increase of shell width.The relative growth rate ranged from 15.44% to 190.91% and the relative weight gain ranged from 8.08% to 44.33%.The seasonal variation range of male and female was 0.47-0.87,more male crabs than female crabs.The b value of growth characteristics of the Eriocheir sinensis was close to 3,and the difference of b values between female and male crabs was not significant.It can be considered that the two crabs grow at the same speed.2.Characteristics of Community Structure of Fishery Resources in Habitat of Eriocheir sinensisIn order to study the characteristics of community structure of fishery resources in the major habitats of Eriocheir sinensis,we analyzed species composition,ecological type,dominant species,diversity index,community structure characteristics and others through setting custom nets in Landshan Sand and Xinkai Sand during June 2016 to January 2017.The results showed that 37 species of fishes(belonging to 8 orders and 16 families)were found in two areas and they were dominated by bottom omnivorous fishes.The dominant species in two areas including Eriocheir sinensis、Macrobrachium nipponense、Chiromantes dehaani and others.The Shannon-Wiener index,Margalef index,Wilhm improvement index and Pielou index of the site where aquatic plant grow were lower than the site where non-aquatic plant,but the result of McNaughton(Dw)index was opposite.Three types of fishery resource community were found by clustering and nonparametric multidimensional scale analysis(NMDS).There were few fish species and low Shannon-Wiener index in Type Ⅰ.The fish community in Type Ⅱ was dominated by Eriocheir sinensis and Chiromantes dehaani.Type Ⅲ has most fish species and highest Shannon-Wiener index in all types.The study showed that there are few fish species in Langshan sand and Xinkai sand,and the community structure of fishery resources is relatively unstable.So it is necessary to repair the community structure of fishery resources in these areas.3.Preliminary Assessment of Habitat of Juvenile Eriocheir sinensisIn order to investigate the habitat suitability status of juveniles Eriocheir sinensis in Langshan sandbar and Xinkai sandbar of the lower reaches of Yangtze River,custom-built netting gears were utilized there from June 2016 to May 2017 so as to obtain the abundance distribution characteristics of juveniles and the six water environmental factors as well.The three factors including water depth,transparency and Chiromantes dehaani abundance were selected after filtering first,the one factor analysis of variance,correlation analysis and canonical correspondence analysis,then habitat suitability curves were established and habitat suitability index was finally calculated.Results of the study revealed that,sites with aquatic plants possessed high abundance of juveniles Eriocheir sinensis.Significant differences within turbidity,transparency and depth of water existed between the sites.The abundance of juveniles Eriocheir sinensis were extremely significant correlated to that of Chiromantes dehaani while the water depth have significantly correlated to water transparency.Sites with aquatic plants in these two areas had relatively high HSI of more than 0.5 than the other sites with lower or no aquatic plants were generally lower than 0.4.However,juveniles Eriocheir sinensis preferred shallow waters with aquatic plants and water transparency between 10 cm and 20 cm.This research study suggests that,the area of these two sandbanks were suitable for the growth and development of juveniles Eriocheir sinensis and more protection is required.