| Eriocheir sinensis is an important economic species in China,belonging to Crustacea,Decapoda,squamosidae and Eriocheir.Chinese mitten crab has the living habits of reproductive migration and bait migration.It inhabits different habitats at different development stages.Therefore,there are some differences in suitable habitat factors such as salinity and sediment.A suitable habitat is conducive to the growth and development of aquatic animals.However,due to the impact of human activities such as wading projects,channel dredging and overfishing,the natural resources and habitat of E.sinensis in the Yangtze River Basin have been seriously damaged in recent years.In order to restore the natural resources of the Yangtze River,a large number of habitat restoration and resource proliferation of E.sinensis have been carried out,and some research has been carried out on its habitat factors.Taking E.sinensis at different developmental stages as the experimental object,this study comprehensively studied the effects of its substrate,concealment,light preference and light cycle on the feeding behavior of E.sinensis at different developmental stages,and systematically mastered the needs of E.sinensis for important habitat factors at different developmental stages,The behavioral preference map of migratory life history is constructed.The research results will provide some reference for habitat restoration,scientific proliferation and release,and resource protection of E.sinensis in the Yangtze River.1.The preference for substrate in different developmental stages of Eriocheir sinensisIn order to explore the preferences of Eriocheir sinensis at different developmental stages for the types of substrates,a single factor experiment method was used to study the effects of E.sinensis on mud,silt(mud: sand=1:1),medium sand(0.35mm-0.50mm)and fine sand(0.25mm-0.35mm)at different developmental stages.The results showed that the preference of parent crab individuals and groups for mud was significantly higher than that of the other three kinds of substrate(P<0.05);The individuals of ovigerous crabs had no obvious preference for substrate,and the preference of the population for mud was significantly higher than that of the other three kinds of substrate(P<0.05);The juvenile crab population preferred mud,followed by silt,which were significantly more than medium sand and fine sand(P<0.05);The preference of button sized crab individuals and populations for mud and medium sand was significantly higher than that of the other two substrates(P<0.05).The results of day and night study showed that there were significant differences in the preference of parent crab individuals and population,ovigerous crab population,juvenile crab population and button sized crab population for substrate during the day and night(P<0.05),but button sized crab individuals at night and ovigerous crab individuals had no significant preference for substrate(P>0.05).The study on the habitat mode shows that the parent crab had no obvious burying behavior;Ovigerous crabs have obvious burial behavior and like to bury in the silt;Juvenile crab like to bury in mud,followed by sediment;Button sized rabs like to bury in mud and medium sand.The study revealed that there were significant differences in the preference of E.sinensis for different substrates,and the preference and habitat of E.sinensis for substrates at different development stages were also different.2.The preference for concealment in different developmental stages of Eriocheir sinensisUsing the method of single factor experiment,the concealment of Eriocheir sinensis in different development stages and its preference for four kinds of concealment: mud,sand,grass and stone were studied,the concealment law of E.sinensis in different development stages and its preference for concealment types were explored.The results of hiding research showed that: E.sinensis have hiding at different developmental stages,and the hiding behavior of parent crabs,ovigerous crabs and button sized crabs during the day was significantly stronger than that at night(P<0.05).The results of the study on the preference of concealment types showed that parent crabs,ovigerous crabs and juvenile crabs had differences in the choice of concealed objects during the day and night,while the button sized crabs had obvious preference for concealment during the day,but no obvious preference at night.Among them,the parent crabs chose stones significantly more than the other three concealed objects during the day,and at night they chose mud and stones more than grass and sand(P<0.05),but had no obvious preference for mud and stones(P>0.05);The ovigerous crabs chose mud and stones significantly more than grass and sand during the day and night;The juvenile crabs prefer aquatic plants during the day,followed by stones,then mud,and finally sand,at night,they prefer aquatic plants,followed by mud and stones,and then sand,with significant differences(P<0.05);The button sized crabs liked mud and stones the most during the day,but had no significant preference for the four kinds of concealed objects at night(P>0.05);3.The preference for light in different developmental stages and the effects of photoperiod on the feeding behavior of Eriocheir sinensisParent crabs,ovigerous crabs and button sized crabs as experimental objects to study their preferences for strong light,low light and darkness,and button sized crabs as experimental objects,three light cycles of full light(24L),full darkness(24D)and imitation natural light(10D14L)were set to study their effects on the food intake,feeding rhythm and hepatopancreatic enzyme activity of the button sized crabs.The results of the study on light preference showed that the preference for the dark environment was significantly higher than that of the weak and strong light environments in the parent crabs,ovigerous crabs and button sized crabs.The results of the study on the effect of photoperiod on the feeding behavior of the button sized crab showed that the photoperiod had a certain influence on the food intake of the crab,and the appropriate light was helpful for the feeding of the Chinese mitten crab.Under full darkness and simulated natural light,the crab had obvious feeding rhythm,under full light,the crab had the same feeding peak with other groups,but there was no obvious feeding rhythm,indicating that the photoperiod had no significant effect on the feeding rhythm of E.sinensis(P>0.05);And there was no significant difference in hepatopancreatic enzyme activity in different photoperiods(P> 0.05). |
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