Investigation Of Integrated Rice And Fishery Farming,aquatic Product Safety Testing,and Analysis And Evaluation Of Crab Farmed In Rice Fields Quality In Southern Shaanxi

Integrated rice and fishery farming is an ecological and green sustainable agricultural model developed on the basis of traditional fish farming in rice fields,using the water surface of rice fields for various kinds of aquatic products farming and obtaining aquatic products while harvesting rice,and it is also an aquaculture model that China has encouraged to develop vigorously in recent years.Hanzhong and Ankang City in southern Shaanxi Province are the main rice growing areas in Shaanxi Province,and also the main development area of integrated rice and fishery farming and the main production area of fishery development in Shaanxi Province.As the main production area of fishery development in Shaanxi Province,the safety of aquatic products under their integrated rice and fishery farming mode determines the safety of aquatic products in the whole Shaanxi Province.Therefore,the experimental project relies on the integrated rice and fishery farming base in southern Shaanxi Province,and samples were taken to investigate the comprehensive benefits and various farming information under each model.At the same time,fish drug and heavy metal ion tests were conducted on aquatic products from several sampling sites in southern Shaanxi Province,and pesticide tests were conducted on benthic aquatic products(river crabs and loaches)and their environmental samples,which are most likely to be enriched with pesticides.As a valuable aquatic product unique to China,the nutritional composition and flavor substances of river crabs are subject to various reasons such as water quality and feed,resulting in large differences in the nutritional composition of river crabs in different regions of the country.The results obtained from the experiment are as follows.(1)The survey showed that there are a total of seven models of integrated rice and fishery farming in southern Shaanxi,namely rice grass carp,rice grass carp mixed farming,rice shrimp and crab,rice crab,rice shrimp,rice carp and rice loach.At present,rice fish(mainly grass carp,carp and crucian carp)is the most common mode,accounting for 59.50%of the total.The benefit of rice shrimp and crab farming is the highest,with an average yield of up to 6,310 yuan per mu.The benefits per unit area of integrated rice and fishery farming in either mode in southern Shaanxi are greater than those of rice monoculture in the same origin.7 modes of rice and fishery farming have different benefits due to the different types of aquatic products farmed.At the same time,because of the proportional relationship between aquatic product yield and the amount of seedlings invested,there are also large differences in the inputs of different aquatic product farming costs.It is more scientific and reasonable to consider the comprehensive input-output ratio and average profit.The input-output ratio of rice crab is better than that of rice fish(1:2.12 and 1:1.97),but the flood resistance of rice shrimp-crab mixed culture and rice crab culture mode is lower than that of rice fish culture mode.The yield per mu of different culture modes in the rice field from high to low were shrimp-crab mixed culture > river crab > loach > crayfish > grass carp mixed culture > grass carp > crucian carp.(2)In southern Shaanxi,six aquaculture bases in Hanzhong and three farms in Ankang were sampled and tested for river crabs,carp,grass carp,bighead carp and mud carp,which were tested for 12 prohibited fish drugs(mainly antibiotics)and four common heavy metals(copper,zinc,lead and cadmium);36 pesticides and their metabolites were also sampled and tested in river crabs,mud carp and their environment in four aquaculture areas in Hanzhong.The test results showed that all the aquatic products met the national safety standards.12 kinds of prohibited fish drugs were not detected,4 kinds of heavy metals were detected but their contents were within the safe range;there were still traces of organochlorine pesticides(aldrin,chlordane,hexachlorobenzene,DDT,6-6-6)enriched in rice,loach and river crab,and only one organochlorine pesticide was detected in the bottom mud of environmental samples(water samples and bottom mud),and 5 kinds of organochlorine pesticides were detected.The five organochlorine pesticides detected did not exceed the standard.It shows that there is no safety risk for aquatic products from integrated rice-fishery farming.(3)After comparing river crabs cultured in paddy fields with those cultured in ponds,it was found that there was no significant difference in the basic nutritional composition(moisture,ash,crude protein and crude fat)of river crabs of the same sex.The nutrient composition of female crab was higher than that of male crab under the comprehensive nutrient composition criteria.There was a significant difference(P<0.05)between the fertility of male crabs in the mixed shrimp-crab culture mode and the monoculture mode in the rice field,mainly because the competition between shrimp and crab in the mixed shrimp-crab culture mode made the male crabs in the mixed culture mode less fertile than the male crabs in the monoculture mode.The free amino acid content of river crabs cultured in rice fields in Chenggu County was lower than that in Yangcheng Lake,Jiangsu Province(literature cited in the paper),probably due to the water source as well as the feed.The high percentage of unsaturated fatty acids(>70%)in the free fatty acid content of river crabs cultured in the rice fields of Chenggu County is very beneficial to human digestion and absorption.This project proved that the safety of fishery products can be ensured under the premise of integrated rice and fishery farming;it also proved that river crabs under the rice and crab farming(rice,shrimp and crab farming)model are rich in flavor and nutrition.