Research On Environmental Preference Of F₂Chinese Sturgeon（Acipenser Sinensis）

Chinese sturgeon (Acipenser sinensis) is a large and anadromous species that only remains in China. It mainly lives in the Yangtze River, the East China Sea, the Yellow Sea and other waters. The economic and social values in Chinese sturgeon are very high. In recent years, the population and spawning grounds of Chinese sturgeon are seriously threatened due to environmental pollution and construction of Gezhouba Dam, Three Gorges Dam and other water conservancy projects. Now, Chinese sturgeon has been listed as national protected species in category I and level CR (Critically Endangered) in red list of IUCN.Complete controlled propagation of endangered animal can protect them from extinction. After more than20years of effort, the complete controlled propagation of Chinese sturgeon succeed which means this species can be continued and the artificial releasing get support. But it is likely to find behavior variation that caused by the adaptation to artificial breeding environment between wild and second generation, because F2Chinese sturgeon comes from the farmed broodstock which has lived in fresh water for more than10years. If it happens, F2Chinese sturgeon may lose some living skill such as migration, avoiding predators and prey, which will threaten its specialties and survival rate in artificial releasing.This study started from the perspective of Behavioral Ecology. In order to find out the habit preference, larvae and juvenile F2Chinese sturgeon were used in test of migration, illumination preference, substrate preference, cover preference and so on. After comparing with the wild group, it could be concluded whether the behavior of F2Chinese sturgeon had changed, and gave advice to artificial releasing and breeding. The main results were as follows:1. We investigated the migration of days-3-14F2Chinese sturgeon. The result showed that days-3-4larvae had a strong migration, their migration rates were48.4%and43.2%. Day-5larvae’s migration rate declined obviously to15.6%, and kept this slow trend to day7. The migration rate closed to0on day8, and continued to day14. There was significantly difference between day-8and days-3-8larvae (P<0.05), while no significantly difference from days-8-14(P>0.05). In summary, larvae F2Chinese sturgeon stopped migration at day8, the same as the F1larvae.2. Preference of white or black substrate was explored by individual test, population test under illuminated situation and population test under dark situation in5-month and7-month juvenile F2Chinese sturgeon. It showed that both5-month and7-month juvenile F2Chinese sturgeon significantly chose white substrate (95%Confidence interval of preference on white substrate does not contain50%), which was the same as wild juvenile. But under dark situation (illumination<0.1lx),5-month and7-month juvenile F2neither chose white substrate nor black one, which was different from wild juvenile. This phenomenon may relate to the intensity of low illumination.3. Illumination intensity preference of5-month and7-month juvenile F2Chinese sturgeon was studied both in individual test and population test. The result showed5-month juvenile individuals significantly chose illuminated area (200～250lx)(P<0.05), while populations preferred transition area (20～501x)(P<0.05). This phenomenon may have relations with the’signal-adaptation hypothesis’, the optimum illumination range and crowding effect in populations. Both7-month individuals and populations preferred transition area (20～501x)(P<0.05). Compared with the exiting wild data, their phototaxis has already declined. Juvenile F2Chinese sturgeon has got an adaptation to artificial breeding illumination.4. The optimum illumination of F2Chinese sturgeon was discussed in individual test. It showed that5-month juvenile F2Chinese sturgeon significantly chose illumination area of45～1351x (P<0.05);7-month juvenile F2Chinese sturgeon had no significantly difference in illumination area of23～2021x (P>0.05). It meant that with the increasing age, F2Chinese sturgeon strengthened its adaptability to illumination.5. Combined individual test, population test under illuminated situation and population test under dark situation to find the substrate (rock, medium gravel, small gravel, sand) preference of5-month and7-month juvenile F2Chinese sturgeon. All result showed that juvenile stayed longest in sand. Juvenile significantly preferred sand to others (P<0.05), except that both5-month individuals and7-month populations under dark situation had no significantly difference between medium gravel and sand. In summary,5-month and7-month juvenile F2Chinese sturgeon chose sand both in the day and night, which is consistent with wild juvenile.6. We explored the cover preference in5-month and7-month juvenile F2Chinese sturgeon individuals. The result showed that both5-month and7-month juvenile F2Chinese sturgeon significantly preferred open waters to cover area (P<0.05), which is the same as wild juvenile.