Study On Selective Behavior Of Anguilla Japonica Larvae To Environmental Factors

The Japanese eel(Anguilla japonica) belonging Anguilliformes, Anguillidae, Anguilla, is a long-distance downstream migration fish. Japanese eel spawning area is located along the western side of the west Mariana ridge, Japanese eel life history include: zygote, leptocephalus, glass eel, elver, yellow eel, silver eel, their entire life history stages need to live in the brackish water of three seawater, freshwater and migratory processes in different habitats conditions.In this study, using on glass eel and yellow eel, glass eel was caught in April 2014 in Yangtze Estuary, average body length(57.52 ± 2.61) mm; mean weight was(0.115 ± 0.025) g. after two months for indoor cultivation, which is yellow eel, the average body length:(90.56 ± 3.63) mm; average weight:(0.68 ± 0.09) g. By studying the Japanese eel glass eel and yellow eel two kinds of developmental stage of sediment color, light intensity and temperature of choice behavior, draw wild Japanese eel on environmental factors preference. Aimed at understanding the Japanese eel in the field of environmental factors in the choice of the situation in order to determine which Japanese eel habitat in the estuary, and trying to analyze verify eel in the estuary area anadromous behavior, presumably on the Yangtze River estuary habitat The adaptive significance.1 Japanese eel on substrate color choice behaviorStudied glass eel and yellow eel for black and white color choices substrate behavior under the indoor natural light(88 lx) and dark(0.3 lx) two light conditions. Experiments at 50 cm × 35 cm × 25 cm deep blue plastic boxes were set black and white colors of the substrate, the Japanese eel recorded in black and white substrate in the activities through the camera; experiment was divided into individual and Two types of groups, that is, each individual experiment to test a test fish, the percentage of statistical experimental fish in black, white matter, respectively, residence time, the experiment is divided into three groups, each 10, a total of 30. Experimental groups of 10 for each test is repeated three times, the percentage of the number of fish in the experimental apparatus in statistical distribution. The results showed that the indoor natural light(88 lx) and dark(0.3 lx) under conditions of individuals and groups of black eel sediment choices with significant(P <0.05); yellow eel individuals and groups are also on the black sediment choices with significant(P <0.05); but glass eel and yellow eel choice of black sediment was no significant difference under two light conditions(P> 0.05). Glass eel and yellow eel choice of black sediment was significantly higher than the white sediment, results indicate that the Japanese eel on a clear preference for black sediment.2 Japanese eel on light intensity of choice behaviorThe experiment is set up four light intensity gradient: 6000 ~ 12000 lx(Area A), 700 ~ 1400 lx(Area B), 60 ~ 150 lx(Area C), 5 ~ 10 lx(Area D). Individuals and groups were divided into two types. The results showed that the percentage of time the eel individuals appearing in Area A, Area B, C and D in the area of the four light intensities, respectively:(3.55 ± 7.03)%,(7.31 ± 9.34)%,(20.42 ± 8.56)% and(68.72 ± 17.17)%; number of eel populations occur in the percentage of the four light intensities are: Area A(2 ± 4)%, Area B(4 ± 4.9)%, Area C(21 ± 9.43)% and Area D(73 ± 13.45)%. Data showed that with the decrease of light intensity, time and number of percentage eel appeared in various regions in order to increase and significant choice Area D(P <0.05).The percentage of time the yellow eel individuals appearing in the four light intensity were: Area A(2.43 ± 0.28)%, Area B(6.55 ± 1.21)%, Area C(19.65 ± 3.01)% and Area D(71.37 ± 2.42) %. Percentage yellow eel populations occur in the four light intensities, respectively, are: Area A(1.67 ± 2.08)%, Area B(4.33 ± 4.04)%, Area C(18.67 ± 5.86)% and Area D(75.33 ± 11.02) %. Data showed that with increasing light intensity, time and number of percentage yellow eel appeared in various regions in order to increase and significant choice Area D(P <0.05).Glass eel and yellow eel at the time and the number of percentage of Area D activities were significantly higher than in other regions(P <0.05), results show that glass eel and yellow eel are on the 5 ~ 10 lx obvious trend of low light. It was speculated that glass eel may select benthic living in low light intensity when migrating upstream through Yangtze estuary, The behavior in this paper indicates that glass eel may migrating by tidal at night, and avoiding predators on day light for effectively migrating to upstream.3 Japanese eel on temperature of choice behaviorThe experiment is set up four different temperature areas, from high to low temperatures were: 26 ~ 30 ℃(Area A), 23.5 ~ 26.2 ℃(Area B), 20 ~ 22.5 ℃(Area C) and 17 ~ 18.8 ℃(Area D). Means the entire temperature range within 17 ~ 30 ℃. Experimental fish holding water temperature(25 ± 0.5) ℃; individuals and groups were divided into two types, the same way as in the previous section, but in groups of experiments extended to 180 min. In addition, in order to eliminate the interference of temperature on fish farming produce, the experimental fish dropped from 25 ℃ to 17 ℃ after adaptation, and then repeat the experiment for the eel. The results showed that the Japanese eel individuals and groups were significantly select A region(P <0.05), yellow eel individuals and groups were also significantly Choose A region(P <0.05). After low-temperature 17 ℃ adapt conducted experimental results show that eel individuals and groups in the percentage of time Area A activity was significantly higher than in other regions, there was no significant difference among the other regions; eel after 17 ℃ adaptation activities in Area A the time and the number of percentage of 25 ℃ experiments after holding the test fish when the results obtained there is no significant difference.Glass eel and yellow eel at the time and the number of percentage of area A were significantly higher than in other regions(P <0.05), the result shows that the Japanese eel preference temperature range of 26 ~ 30 ℃. The results of Japanese eel provide certain reference value and significance for the aquaculture.