Research Of Interspecific Relationship Between Procambarus Clarkii And Two Other Indigenous Crustacean(Eriocheir Sinensis And Macrobrachium Nipponense)

This study was designed to investigate the interspecific relationship between the red swamp crayfish(Procambarus clarki) and the Chinese mitten crab(Eriocheir sinenis), and also between the red swamp crayfish and the other crayfish (Macrobrachium nipponense). Three experiments were performed from three aspects which were agonistic behavior,signal selection and polyculture.Experiment I:The behavior of red swamp crayfish and Chinese mitten crab which have the same weight was observed in a relatively small polyculture system. The agonistic behavior in the first30minutes after the encounter and the results of the polyculture was recorded; The behavior of crayfish toward or away from a bigger crab was observed in the "Y" maze. The results show that the times of active attacks and approach of crayfish, total times of active attacks and approaches of crayfish were significantly more than crab(P<0.05).After30days’of polyculture, in30%groups, crayfish died, while, only10%groups of crab was dead, and60%of the groups they coexist. In the second experiment, with the increase of trial numbers, the tendency of the choice between blank and crab for crayfish turn from insignificant to be more significantly favored blank(P<0.05). Which means the ability of crayfish to recognize crab have significantly improved, and the choice behavior of crayfish was obviously inhibited.Experiment II:Dominant and subdominant crayfish were marked by agonistic encounter one-to-one in tank,and then one dominant or subdominant crayfish was cultured with one crab at the same weight level as a group.There were90groups in all.The number of dead crayfish was recorded during the experiment. The results showed that there were13groups in which crayfish survived while crab died, the ratio of dominant and subdominant was8:5.Hierarchical status of crayfish has no significant effect to the interspecific competition of crayfish and crab.Experiment III:The interspecific relationship between Procambarus clarkii and Macrobrachium nipponense was investigated from four aspects:interspecific agonistic behavior, the effect caused by hierarchical status of crayfish to interspecific agonistic behavior with Macrobrachium nipponense, the response of juvenile crayfish to signal of Macrobrachium nipponense,and the polyculture of Procambarus clarkii and Macrobrachium nipponense. The results show that, in agonistic experiment of adults, times of active attacks by red swamp crayfish was significantly more than freshwater shrimp (P<0.05); times of active attacks and approach by freshwater shrimp were significantly more than red swamp crayfish on the same weight level(juveniles)(P<0.05); Less escape behavior of dominant red swamp crayfish happened to freshwater shrimp while more escape behavior of subdominant red swamp crayfish happened to freshwater shrimp; Red swamp crayfish larvae showed significantly avoiding behavior to freshwater shrimp (P<0.05); The ratio of groups in which red swamp crayfish died while freshwater shrimp survived was26.7%,and60%of the groups they coexist.This research indicated that the adult red swamp crayfish is an invasive species;Passive defense strategy was used by juvenile red swamp crayfish when encountered freshwater shrimp on the same weight level.;Subdominant red swamp crayfish had more escaping behavior to freshwater shrimp than dominant individuals;Red swamp crayfish larvae showed avoidance to freshwater shrimp;It is feasible to culture red swamp crayfish and freshwater shrimp in polyculture system with suitable condition.