|Other Abstract||Since the production of the first batch of transgenic fish, more than 30 varieties of transgenic fish have been successfully generated all over the world. The host fish include many of the major world aquaculture specie, e.g., common carp (Cyprinus carpio), tilapia (Oreochromis niloticus), channel catfish (Ictalurus punctatus), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss) etc. These transgenic fish have shown different aquaculture-related performance, including accelarated growth performance, increased food conversion efficiency, cold resistance, disease resistance and so on. However, there is no one case of transgenic fish in commercializaiton. One of the major concerns is the ecological safety issue after the environmental release of transgenic fish. It has been an indispensable step for us to evaluate the potential ecological risk thoroughly and substantially, before the marketing of transgenic fish. This is not only a necessary and challenging issue in the field of transgenic fish, but also critical for the breeding purpose of transgenic fish. Nevertheless, there is no widely accepted theory and/or well-developed approach for us to evaluate the ecological risk of transgenic fish to the environment.
1. Focusing on the evaluation of ecological risk of transgenic fish, in this study we constructed the largest and even the only artificial lake eco-system for ecological study of transgenic fish. Subsequently, all-fish growth hormone (GH) transgenic common carp and their non-transgenic controls were released to this lake for a long time observation. First, the viability, growth performance and feeding habitats of transgenic fish were studied. Second, the impact on its major food species, i.e., big benthic animals, was studied in the following aspects, community organization and function, and bio-diversity dynamics. The main results were listed as follows.
2. An artificial lake eco-system for the study of transgenic fish was constructed successfully. We designed and built a experimental lake with flood control, escape prevention, and guard against thief. The main objectives are to conduct a comparative study between the transgenic carp and the control carp on several aspects of biological characters, such as viability, growth performance, feeding ecology and reproduction pattern, to evaluate the community ability of transgenic carp and their potential impacts on other species in the same water body. This has provided a novel platform for the evaluation of the ecological risk of transgenic fish.
3. The physicochemical factors of the water body and many biologically important taxa in the lake were examined. Three years after the construction of the lake, the transplanted aquatic plants showed a good growth performance, the released molluscs, shrimps and fishes not only survived, but also normally reproduced to establish population, suggesting that the transplanted organism have been a good acclimatization to the lake. Importanly, there are 26 species of fishes belonging to 12 families and 23 genera in the experimental lake, in which the cyprinid fish are dominant, contributing 65.2% to the total. In the fish community of the lake, crucian 3 dominant species. The ichthyologic fauna of the lake is similar to that of the lakes along the middle and lower reaches of the Yangtze River, and thus the experimental lake should be representive of the lakes.
4. After the release of transgenic fish, the spatial distribution of different water circumstances, the coposition and density of planktons, and the chlorophyl content were tracked and analyzed. As a relative unopened circumstance, the experimental lake is under the status of mid-nutritional, and it shows no significant variety in the physical and chemical factors of the water in different sampling time points, and little difference in the planktons from different sampling positions. By this, we set up a DNA topology technology of planktons, providing a good foundation for further study on the impact of transgenic fish on planktons.
5. The surviaval and growth performance of transgenic carp were studied in the experimental lake. In 2006 and 2008, transgenic carp took 18.5% (n=108) and 20% (n=60), respectively, among the random captured carps. Compared with the release time of transgenic fish, this percentage decreased quite a lot (X2 test, p = 0.0000), suggesting that transgenic carp have lower viability than the control carp. Among the survived common carp, transgenic common carp showed 9.8% higher specific growth rate (SGR) in body length than the control, 11.3% higher SGR in body weight than the controls. Fast-growth performance of transgenic carp relative to the control was measured in the first year, which was not found in the next two years of the experimental period.
6. The feeding ecology of transgenic carp was studied in the experimental lake. Either 1-year old or 3-year old, the consumed taxa or diet groups were similar between the transgenic carp and the control . The difference between them in the food composition was found, but this difference tended to reduce with the increase of fish age. The transgenic fish is omnivorous with a preference of animal foods, and its feeding habits is similar to the control carp. At 1-year old, transgenic carp showed a lower diversity of food organisms than the control carp, and their ecological overlap index (EOI) was quite low (0.332), indicating their differentiation of ecological niche. At 3-year old, they showed a similar food composition, and consequently the EOI is fairly high (0.942) which suggests that the trophic relation between them is very intense.
7. The change of community organization and function, and biological diversity of big benthic animals was studied after the release of transgenic carp. 2 years after the release of transgenic carp, the composition, density, biological quantity, and diversity index of benthic animals somehow showed decreases; while 3 years after the release of transgenic carp, all these parameters began to get recovered. Overall, the diversity index decreased 19-44% on average, uniformity did not show any difference, species richness was reduced about 38%. All these indicate that the release of transgenic carp has a negative impact on the community organization and bio-diversity of benthic animals at this moment, while the substantial influence onthe organism community, and the recovery and healthy condition of aquatic eco-system need to be examined and studied in a long time.
Keywords: GH-transgenic common carp(Cyprinus carpio), ecological risk, survival and growth performance, feeding ecology, community structure, bio-diversity, artificial lake eco-system|