Effect Of Growth Environment And Diet On Growth And Development Of Juvenile Crayfish (Procambarus Clarkii)

The Procambarus clarkii(Cirard) named red swamp crayfish,belongs to Decapoda,Reptantia,Cambaridae,Procambarus,and is commonly known as freshwater lobster.Procambarus clarkii origined from North America,is introduced in Japan in 1918,and imported to nearby Nanjing in China since the late 1980s.It has both strong adaptability and breeding rapidly,and now is distributed in lakes and drains from more than a dozen provinces and municipalities in China.As a result of Procambarus clarkii like burrowing and cave-living,which has some destructions on crops,pond and the dam. In the past,farmers have to remove it as pest.But in recent years,because of Cambarus shrimp tasting delicious,nutritious and relatively inexpensive features,it is welcomed by more and more consumers and has become the main aquatic products in mainland market. As the increasing consumption of P.clarkii,the market demand exceeds supply,rising prices have also promoted P.clarkii cultured industry.However,the current domestic P. clarkii is still basically under the conditions of natural breeding and artificial fishing,and the artificial breeding technology is not quite perfect.Researchers have done some work on the breeding of P.clarkii,however,there is no reports yet concerning the systematic research on the necessary environmental and nutritional conditions for the larval growth and development.In larval stage,as a result of its rapid growth,high molting frequency and weak disease resistance,the growth environmental conditions can directly influence P.clarkii larvae survival and growth rate.What's more,different diet have also important implications on the larval growth.In order to search for the conformable environmental conditions for P.clarkii larvae growth and development,and to find out the diet promoting larvae survival and growth rate,this study is based on the research on growth and reproduction of P.clarkia early in our laboratory.By using orthogonal design method L9(3³),we made a study on the growth environment for P.clarkii larvae;explored respectively different photoperiod,calcium ion concentration and pH influence on larvae growth and survival,we also made a further research on P.clarkii larval stage feed with a view to P.clarkii artificial breeding,especially to provide some guidance for seed rearing.The results are summarized as follows:1.The effects of different photoperiod,water calcium ion concentration and pH on P.clarkii larvae survival,growth and molting.In this orthogonal experiment,three environmental factors were settled at three different levels respectively(photoperiod: 16L:8D,12L:12D,and 8L:16D;calcium concentration:45.5 mgL^-1,65.5 mgL^-1,and 85.5 mgL^-1;pH:6.8,7.8,and 8.8).Statistical significance of the results were evaluated by variance(方差) analysis.Range analysis showed that the highest survival rate of juvenile crayfish occurred at photoperiod of 16L:8D or 8L:16D,water calcium concentration of 45.5 mgL^-1,and pH of 7.8;the maximum weight gain at photoperiod 16L:8D,water calcium concentration 65.5 mgL^-1,and pH 7.8;the maximum length increase at photoperiod 16L:8D,water calcium concentration 65.5 mgL^-1,and pH 7.8; and the highest molt frequency at photoperiod 12L:12D,water calcium concentration 65.5 mgL^-1,and pH 7.8.方差analysis indicated that photoperiod,water calcium concentration,and pH all significantly influenced the weight gain of juvenile crayfish(P＜0.05).According to the experimental results,and considering both the survival and growth factors,a photoperiod of 16L:8D,calcium concentration of 65.5 mgL^-1,and pH 7.8 might be the optimal conditions for rearing P.clarkia larvae.2.The effects of different diets on the growth of Procambarus clarkii larvae.The beginning of the experiment is at the stage of P.clarkii larvae hatching from mother to start feeding,and the experiment period is 40 days.Randomly selected larvae from the same mother as the experimental materials,and choose five different bait feeding: Artemia;Chironomid larvae(pure red worms);feed 1(laboratory preparation);feed 2 (laboratory preparation);grass carp surimi.The results show that,different diets influences on Procambarus clarkii larvae survival rate were as follows:the best group Artemia(100%);Chironomid larvae(90%);feed 1(90%);feed 2(80%);and the worst group-grass carp surimi(50%).Different diets effects on P.clarkii larvae growth of body weight:the best group of Chironomidae larvae,up to 7034%;followed by Artemia, feed 1,feed 2 and grass carp surimi group is only 400%in the worst.From the results we can see that,considering whether survival rate or the weight growth,Chironomidae larvae may be the quite conformable diet for P.clarkii larvae.What's more,compared with the feed 2,because of adding the appropriate amount of vitamin C and fish oil,feed 1 had much better efforts.As a result,adding the proper amount of vitamin C and fish oil in feed may be more conducive to P.clarkii early larval survival and growth.