| Procambarus clarkii(crayfish)is an important economic shrimp in the world.Most people only see its economic benefits.However,as an invasive species,crayfish itself is also a very serious damage to the invasion zone.With the rapid development of world economy and the diversification and complexity of human activities,many important freshwater resources lakes have been introduced crawfish.Caohai,the largest natural freshwater lake in Guizhou Province,introduced a large number of crawfish in the form of releasing in 2012.This study is based on the invasion of crayfish in Caohai wetland,and the invasion of crayfish to eat a large number of local fish and shrimp,the edge of Caohai wantonly dig holes to endanger the ecological environment security of Caohai,taking crayfish as the research object,by means of field monitoring,trapping,investigation and salvage,indoor culture observation,anatomical statistics and experimental analysis,the trapping effect of five kinds of common trapping agents on crawfish in Caohai wetland,the population distribution and activity law of crawfish invading in Caohai wetland were studied systematically.The main results are as follows:(1)Study on the trapping effect of 5 kinds of different trapping agents on crayfish.Five kinds of common traps,such as fresh pig liver,pig heart,pig blood,rapeseed oil residue and "shrimp eel one pot" fish and shrimp entrapment agent,were used to entrap crayfish in the field.After 12 months of entrapment comparison,the average entrapment amount of five kinds of common entrapment agents was analyzed: oil residue > pig liver > pig heart > pig blood > shrimp eel one pot "entrapment agent,and the maximum entrapment amount was the same: Oil residue > pig liver > pig heart > pig blood > attractant of "shrimp and eel in one pot";the trapping effect of various attractants has a significant positive correlation with water temperature and temperature,but not with other environmental factors.(2)Population distribution of crayfish in Caohai wetland.After 12 months of trapping and fishing investigation on crawfish in Caohai,it is found that there are many crawfish populations in wujiayantou,jiangjiawan and Xihai wharf,but most of them are in swamp wetland and phreatic water area.Generally,there are many crawfish populations in areas with water depth less than 2m,scattered in areas with water depth of 2-2.5m,and no distribution in areas with water depth greater than 2.5m.Crawfish species are found near Luoluo mountain The distribution of the population is general,but there are crayfish traces in the marshes of liujiaxiang,baijiazui,Zhujiawan and huyelin,but the distribution of the population is low.(3)Monitoring of Caohai water quality.After one year,according to the national standards for monitoring various indicators,the water quality of Caohai was monitored on a monthly basis,and the overall situation of Caohai water quality was found to be poor.Among the indexes such as dissolved oxygen,permanganate index,COD,BOD5,ammonia nitrogen,total phosphorus and total nitrogen,dissolved oxygen,permanganate index and ammonia nitrogen are often within the standard of class III water,and BOD5,COD and total nitrogen reach class V or even worse.(4)The correlation between the size,sex ratio and distribution of crawfish in Caohai and water environment was studied.Pearson's analysis of individual size,male female ratio and distribution of crawfish in Caohai and water quality indicators showed that there was no significant correlation between individual size and water quality indicators;there was a significant positive correlation between male female ratio of crawfish and water dissolved oxygen;there was a significant positive correlation between crawfish distribution and water temperature,and there was a significant correlation between ammonia nitrogen,total phosphorus and total nitrogen Negative correlation.(5)Study on the activity of crawfish in Caohai.Through the observation of 600 healthy and vigorous crawfish in Caohai,the statistical analysis shows that the daily activity of crawfish in Caohai starts from 6 to 8 in the evening and stops before 6 in the morning.After trapping and fishing,it was found that the annual activity of crayfish in Caohai began from March to April,and gradually weakened from October to November.However,from November to march of the following year,there are still signs of activity,but relatively weak.(6)Research on reproductive strategy.The results showed that the breeding season of Caohai crayfish was from May to July,and most of the eggs were in the range of 100-400,and there was a significant positive correlation between the number of eggs and the body size. |
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