In order to explore the way of water spinach planting in floating bed affecting the water micro-ecological environment of tilapia aquaculture ponds, water spinach floating beds were set up in the ponds under the 10% coverage. These ponds served as the treatment group, while the other ponds without floating beds served as the control group. After the vigorous growth of water spinach, the samples of water from treatment ponds, control ponds, and the samples of water spinach roots were collected respectively. The DNA of the samples was extracted, part of them was used to amplify the 16S rRNA genes and carry out the high-throughput sequencing, to investigate the effect of water spinach planting on the bacterial community structure in water, and analyze the relationship between the root system of water spinach and the bacterial community structure of surrounding water. Another part of DNA was used to conduct the fluorescent quantitative PCR to determine the copy number of nitrogenase gene, and analyze the effect of water spinach planting on the nitrogenase genes in tilapia aquaculture pond ecosystems. The results showed that the direct effect of water spinach planting on the community structure of planktonic bacteria in the water was not significant; however, the root biofilm of water spinach played an important role as a key part of the pond micro-environment. At the same time, water spinach root biofilm also increased the number of nitrogen-fixing microorganisms per unit volume in pond water.

In this paper, we optimized the determination method for geosmin (GSM) and 2-mathylisoborneol (2-MIB) in aquaculture water and aquatic products by using the method of microwave distillation - solid-phase microextraction - gas chromatographic-mass spectrometry (MD-SPME-GC-MS). We optimized the four pre-treatment processing parameters, including carrier gas rate, microwave power, distillation time and collection method, and determined the experimental conditions as follows: carrier gas rate of 60 mL/min, microwave power of 400 W, distillation time of 6 min, and constant of 250 mL. In aquaculture water, the detection limit of GSM and 2-MIB reached 1 ng/L and 10 ng/L, respectively. In aquatic products, the detection limit of GSM and 2-MIB reached 0.025 μg/kg and 0.25 μg/kg, respectively. The standard curve of this method had good liner relation in the range of 1-200 ng/L and 10-200 ng/L (R² was 0.9997 and 0.9982, respectively). The average recovery rate of GSM and 2-MIB at different concentrations (1, 5, 7, 10, and 20 μg/kg) was 45.28%-49.92% and 82.15%-87.36%, respectively. In this experiment, the water samples and aquatic product samples from Wuxi were detected by this method. The result showed that the average concentration of GSM and 2-MIB in the water samples was 19.58 ng /L and 58.29 ng /L, respectively. In aquatic products, only GSM was detected, and the average concentration was 0.61 μg/kg. This method can be widely used to detect fishy substances in aquaculture water and aquatic products.

In order to grasp the water flow conditions suitable for fish growth, a systematic review was conducted on the behavioral characteristics and physiological metabolism of fish at home and abroad under different water flow conditions. The effects of water flow on water quality and the behavioral differences of different fish stimulated by water flow were analyzed and compared, and the effects of water flow on fish from the perspective of fish physiological metabolism was explored. The results show that the maximum water velocity that fish could withstand is generally related to body length (BL), and lower water velocity (<0.5 bl/s) has no significant effect on fish, higher water velocity (>2 bl/s) has more negative effects on fish behavior, survival rate and physiological metabolism, while medium water velocity (0.5-2 bl/s) is suitable for fish growth, which can improve fish immunity and enhance antioxidant level of fish. The current research on fish tolerance to water velocity was discussed and optimized from an experimental perspective in the study, in order to obtain a more accurate growth-flow velocity curve.

Opsariichthys bidens and Acrossocheilius hemispinus are two kinds of indigenous freshwater fish in Fujian Province. They have good market foundation, development potential and broad promotion prospects. However, in the process of large-scale artificial breeding, it is found that the parent fish of the two indigenous freshwater fish have common problems such as slow gonadal development, poor synchronization, low amount of eggs and poor egg quality, which seriously affect the industrialization process of the two fish varieties. The strengthening cultivation of parent fish is beneficial to improve fish reproductive performance in order to obtain a large number of high-quality fish fry, so the strengthening cultivation of parent fish is particularly important. At present, the study of strengthening cultivation of parent fish has become an important, complex and extensive research topic. This paper expounds on the research status of strengthening cultivation of parent fish of the two indigenous freshwater fish from the aspects of parent fish strengthening concept, strengthening methods (nutritional strengthening and environmental stimulation) and parent fish conservation scheme. This paper also analyzes the current problems and shortcomings in the cultivation, and puts forward corresponding suggestions, so as to promote the high-quality development of Opsariichthys bidens and Acrossocheilius hemispinus.

In recent years, with the rapid development of the aquaculture industry in China, the aquaculture production has been increased significantly, but at the same time, it has also caused problems such as aquaculture water pollution. Aquaculture wastewater treatment is an important practice of the development concept of “lucid waters and lush mountains are invaluable assets”, and it is also an inevitable requirement for promoting the green and high-quality development of aquaculture industry. Taking Anhui Province as an example, this study summarized and analyzed the current situation of aquaculture and its wastewater treatment, and the typical models of wastewater treatment, then pointed out some existing problems and proposed countermeasures and development suggestions, aiming at providing reference for the transformation and upgrading, as well as the green and high-quality development of the aquaculture industry in Anhui.

Collective behavior is a common phenomenon in nature, about half of all fish species shoal for part or all their lives. In order to investigate the effect of population size on the collective behavior of juvenile bighead carp (Hypophthalmichthys nobilis), the Lolitrack software was used to compare the differences in spontaneous swimming speed and spatial distribution among experimental fish populations with different numbers of individuals in this study. The results showed that the spontaneous swimming speed of juvenile bighead carp was mostly in the range of 0-6 cm/s, and there was no significant difference in the average swimming speed among populations with of 1, 2, 4 and 8 individuals, indicating that the population size had no significant effect on the spontaneous swimming speed of juvenile bighead carp. The synchrony of all experimental groups were high and significantly decreased with the increase of population size (P<0.05). The nearest neighbor distance (NND) and mean neighbor distance between the focus fish and other experimental fish in the population were mostly distributed at 2-8 cm and 4-14 cm, respectively. The NND of the population with 2 individuals was significantly higher than the population with 4 and 8 individuals (P<0.05). The polarity of populations with 2 (83%) and 4 (88%) individuals were significantly higher than that with 8 individuals (68%, P<0.05). In conclusion, these findings indicate that juvenile bighead carp has obvious collective behaviors. On the one hand, the population size has little effect on the spontaneous swimming speed of juvenile bighead carp, and on the other hand, the population size has significant effect on its spatial distribution. In this study, the effects of population size on the cluster parameters of bighead carp are investigated, and the study is of practical significance for ecological breeding and fishery management of economic fish.

China has a remarkably long history of aquaculture. At present, aquatic products have become a main way of protein intake for human body under the rapid economic growth, but there are some restricting factors for the sustainable development of aquaculture industry, including the industrialized and high-density breeding mode, unscientific breeding technologies and other external pollution, so the quality of aquatic products cannot be effectively guaranteed. This paper introduced current pollution status of aquaculture, analyzed the source of pollution in detail, and put forward effective countermeasures for achieving the sustainable development of aquaculture and ecology.

The Yalu River flows through Jilin and Liaoning Province. Because of its special geographical condition, climate environment and fish fauna composition, there are many special economic fish species. In recent years, in order to meet the needs of aquaculture farmers and consumers, a lot of research work has been done on the development and utilization of fish resources in the Yalu River, which has played an important role in promoting the freshwater fishery in Liaoning Province and increasing aquaculture farmers’ income. The paper summarized the characteristics of fish resources in the Yalu River, the development and utilization of the main economic fish resources such as Hypomesus transpacificus, Plecoglossus altivelis, Siniperca scherzeri, Hemibarbus labeo and Odontobutis yaluensis, and the present situation of fish breeding. Some suggestions were put forward, including the investigation of fish resources in the Yalu River, the management of cage culture, the selection of fine species and the development of feed.

Wastewater from aquaculture has attracted wide attention as one of the sources of agricultural non-point source pollution, and the management of aquaculture wastewater has become a current research hotspot. In order to understand the mechanism of aquaculture wastewater purification and enhance the purification technology efficiency, this paper introduces the current status, hazards, and related control policies of aquaculture pollution in China, and reviews the aquaculture wastewater purification technologies developed in the past two decades. Finally, the research direction of aquaculture wastewater is discussed to put forward the possibility of strengthening the sedimentation unit, and using new materials and microorganisms to intensify the purification system.

The establishment of characteristic columns is of great significance to enhance the influence of popular agricultural science periodicals, to realize ‘dislocation competition’ and ‘characteristic journal management’ and to make the periodicals have ‘irreplaceable’ inner quality. Taking the Special column designed by the journal of Scientific Fish Farming as an example, the column is characterized by recording the industry process and serving the fishery economy. The column follows the guidance of national policies, highlights the planning awareness and focuses on hot spots, and it plays an important role in the spreading of information on meteorological disaster emergency, fishery food safety, development of rice-fish integrated farming model, and ‘company+fishery’ business model. The results show that the success of characteristic columns has promoted the brand construction of the periodical, and the publishing practice could be used as reference by peers.

This study aims to investigate the differences of biological indexes and meat nutrients of Cyprinus carpio from earth pond reared mode and rice field reared mode (earth pond reared is defined as ER and rice field reared as RR, respectively). Three ER and three RR carps (approximately 800 g) were collected to measure and compare the biological indexes. In addition, the contents of conventional nutrients, amino acids and fatty acids of meat were analyzed and compared between ER and RR. The results showed that the condition factor and meat yield of ER were significantly higher than those of RR, while higher caudal peduncle length/caudal peduncle depth ratio was recorded in RR. Higher contents of crude fat, crude protein, ash, total essential amino acids, total nonessential amino acids, total amino acids and total monounsaturated fatty acids, and the essential amino acid score of meat were detected in ER, while significantly higher contents of total polyunsaturated fatty acids, ∑n-6 PUFA, and total highly unsaturated fatty acids were recorded in RR. In conclusion, the RR has slender body, lower meat yield and lower conventional nutrient contents; the meat amino acids contents of ER are higher than that of RR, while the meat fatty acids composition of carps of the two modes has their own advantages, respectively.

The study aims to further obtain information about antibacterial control measures in major trading countries of aquatic products, improve the maximum residue limit (MRL) standard system of fishery antibacterials in China’s aquatic products and enhance the quality and safety level and international competitiveness of China’s aquatic products. The maximum residue limit standard systems of fishery antibacterials in aquatic products of China, Codex Alimentarius Commission (CAC), European Union (EU), and major trading countries (the United States, Japan and etc.) were compared in this study. Besides, the similarities and differences between China and major trading countries in maximum residue limits for fishery antibacterials were analyzed. The results indicate that there are differences in the quantities, limit values and drug types for fishery antibacterial MRLs in aquatic products between China and the above countries and international organizations, among which Japan sets the most maximum residue limit standards with 31 items, followed by EU with 26 items, China with 22 items, CAC and the USA with 5 items. Aiming at the existing problems of maximum residue limit standards for fishery antibacterials in China, this study puts forward suggestions on increasing the basic research of fishery antibacterials, taking a leading role or actively participating in the formulation of fishery antibacterial MRLs, keeping up with the development trend of international standards and strengthening international cooperation and exchange.

To improve the germplasm of yellow catfish (Pelteobagrus fulvidraco) under cultivation in Tianjin and increase the economic and ecological benefit of the cultivation, a new breed of hybrid yellow catfish ‘Huangyou 1’ was introduced to Tianjin in 2019 by the research group. The growth, disease resistance and production of nitrogen and phosphorus were studied systematically by comparing characters. The results showed that the growth rate and weight gain rate (WGR) of hybrid yellow catfish were significantly higher than those of common yellow catfish (P<0.05), and the feed conversion ratio (FCR) was lower than that of common yellow catfish, but the difference was not significant (P>0.05); the main death diseases of hybrid yellow catfish were body surface ulceration and gill rot. There was no significant difference in the incidence of body surface ulceration between hybrid yellow catfish and common yellow catfish (P>0.05). The incidence of gill rot in hybrid yellow catfish was significantly higher than that of common yellow catfish (P<0.05), while the incidence of other diseases was significantly less than that of common yellow catfish (P<0.05). The total survival rate of hybrid yellow catfish was significantly higher than that of common yellow catfish (P<0.05). The increment of ammonia nitrogen, nitrite and total phosphorus in the tail water by gaining 1 kg body weight of hybrid yellow catfish was significantly lower than that of common yellow catfish (P<0.05). Although the increment of total nitrogen in the tail water by gaining 1 kg body weight of hybrid yellow catfish was also less than that of common yellow catfish, the difference was not significant (P>0.05). Therefore, the characters of growth, disease resistance, nitrogen and phosphorus production per unit weight gain of hybrid yellow catfish ‘Huangyou 1’ are better than those of common yellow catfish, and hybrid yellow catfish ‘Huangyou 1’ is suitable to be popularized and cultured in Tianjin.

The preliminary study showed that the integrated mode for water quality control, named as “5% water spinach (Ipomoea aquatica Forsk.) + 10% filler + algae splashing (Chlorella pyrenoidose)” is worth popularizing. To further verify the effect, the purification effect of different water spinach planting ratios on nitrogen and phosphorus in pond water was studied. Water quality indexes, such as TN (total nitrogen), NH₃-N (ammonia nitrogen), TP (total phosphorus), COD_Mn (permanganate), TSS (total suspended solid), pH and DO (dissolved oxygen), were determined by setting the planting proportion of 5%, 8% and 10% of water spinach, the environmental and economic benefits were also evaluated. The results showed that the TN, NH₃-N, TP, COD_Mn and TSS in tilapia pond were reduced to a certain extent by the cultivation of water spinach. The removal rates of TN and TP were 10%-15% and 20%-40% respectively. The 5% water spinach planting group also had the good removal effect on NH₃-N and COD_Mn, and the economic benefit of this mode was good, which was suitable for application.

As the core of industry 4.0, Internet of Things technology has become a hot word around the world. As a large agricultural country, in agricultural production, China needs to introduce new technologies to construct a production mode with less consumption, pollution avoidance, low cost and mass production in limited resources. This paper introduces IOT technology combined with Siemens S7-1500 controller, node-red and other Internet of Things tools, connecting sensors and PC station to form a set of PLC controlled fish vegetable symbiosis system. TIA portal serves as the programming configuration software to configure and test the sensor and controlled object, to design the electrical system, to assemble the electrical cabinet of the external control system, and to realize the automatic control of the fish vegetable symbiosis system. The design changes the traditional high-density farming mode, and could act as another type of integrated farming mode imitating nature. It holds the characteristics of low energy consumption, high yield, high profit, good product and no pollution.

To study the fish community structure and their correlation with environmental factors in Zhenjiang Hechang section of the Yangtze River, the fishery-annual survey was conducted in November of 2016 to October of 2017. The Redundancy analysis (RDA) was used to study the correlation between fish community and environmental factors in this section. A total of 79 species were collected, which belongs to 57 genera, 17 families and 9 orders. The Cypriniformes had the maximum ratio. The results show that orthophosphate, water temperature and water depth have significant influence on the composition of fish community (P<0.05). Ctenopharyngodon idellus and Carassius auratus have the biggest correlation with the concentration of orthophosphate, Elopichthys bambusa and Hemiculter bleekeri have the biggest correlation with the water depth, Culter alburnus and Mylopharyngodon piceus have the biggest correlation with the water temperature. The tide is also a key factor affecting the composition of fish community, which is generally manifested as a large number of fish species and quantity in the spring tide period, but the difference is not significant. The research could supplement the basic data of fish and provide a scientific basis for the assessment and protection of fishery resources in the Yangtze River basin.

In order to screen out the synergistic tank mixtures that have a synergistic effect on the control of Bemisia tabaci Gennadius and Myzus persicae Sulzer, the leaf dip method was used to determine the co-toxicity of rotenone with clothianidin, thiacloprid and thiamethoxam. The tank mixtures with better effect were screened through the co-toxicity coefficient, and then the field efficacy test on Bemisia tabaci Gennadius and Myzus persicae Sulzer was carried out. The results showed that 12 groups of tank mixtures had a synergistic effect on Bemisia tabaci Gennadius and 6 groups of tank mixtures had a synergistic effect on Myzus persicae Sulzer. Among them, 5 groups of tank mixtures have synergistic effects on both Bemisia tabaci Gennadius and Myzus persicae Sulzer. When rotenone and clothianidin were proportioned according to the active ingredients of 3:20, 14:25 and 13:25, and rotenone and thiamethoxam were proportioned according to the active ingredients of 63:10 and 133:1, all combinations had synergistic effects on Bemisia tabaci Gennadius and Myzus persicae Sulzer. Field efficacy test results showed that the control effects of the tank mixtures of 6% rotenone microemulsion with 20% clothianidin suspension on Bemisia tabaci Gennadius and Myzus persicae Sulzer were 70%, 90%, 92%, 88% at 1, 3, 7 and 10 days after treatment respectively. The control effects of the tank mixtures of 6% rotenone microemulsion with 25% thiamethoxam water dispersible granules on Bemisia tabaci Gennadius and Myzus persicae Sulzer reached 74%, 86%, 91%, and 90% at 1, 3, 7 and 10 days after treatment respectively. The quick-acting effect was better than the control effect of 6% rotenone microemulsion, and the lasting effect was better than the control effect of chemical pesticides. Rotenone and 3 kinds of neonicotinoid insecticides have a significant synergistic effect in tank mixtures, and the study could provide a theoretical basis for the field pesticide reduction control of Bemisia tabaci Gennadius and Myzus persicae Sulzer.

To provide technical parameters for the research and improvement of fish pump, the damage comprehensive evaluation method of vacuum fish pump was established by means of Principal Component Analysis (PCA). Experiments on Carassius auratus were carried out by vacuum fish pump to obtain fish body damage data. A comprehensive injury evaluation model was established by measuring the injured surface area ratio, 24-hour survival rate, red blood cell number, white blood cell number, superoxide dismutase activity, alanine aminotransferase activity and creatinine content. The results showed that the cumulative contribution rate of three principal components extracted by PCA was 78.232%, which could represent most of the fish damage. The comprehensive evaluation model of fish damage by vacuum fish pump was F=0.285X₁+0.111X₂+0.316X₃+0.366X₄-0.118X₅+0.234X₆. There was no significant damage to the surface and viscera of fish by vacuum fish pump, and the comprehensive score was -0.102, which was close to that of the control group, indicating that the damage effect of vacuum fish pump on fish was very small. The results of experiments show that SOD activity, white blood cell count and body surface damage area ratio are the data indexes that have great influence on damage evaluation. The comprehensive damage evaluation model established by PCA can be used as a feasible method to evaluate the damage of fish, which provides a powerful reference for the improvement of fish suction pump.

To study the dynamic degradation regulation of fenvalerate (FV) and its chiral isomers (trans-isomer: FV1 and FV2; cis-isomer: FV3 and FV4) in aquaculture sediment, the degradation regulation of FV and chiral isomers were studied through laboratory simulation. The degradation of FV in sediment followed the first-order degradation kinetics. The half-lives of FV in the sediment ranged from 19.47 to 38.73 days. There was no significant difference in the degradation half-lives of FV. Nevertheless, the half-lives of different chiral isomers in the sediment were different. The degradation half-life of FV1 was substantially longer than those of other isomers, and the degradation half-life of FV3 was significantly longer than those of FV2 and FV4. FV underwent α-C isomerization in the sediment. When the conversion was carried out for 21 d, the conversion rate was slowing down and the changes in conversion products decreased. Because FV had a long accumulation period in sediments, the direct exposure of sediment to FV should be minimized. To effectively conduct environmental and ecological risk assessments of FV, the different chiral isomers should be distinguished in sediment FV residues.

To study the effects of different feeding rates on the growth, water physicochemical indexes and microbial community metabolic diversity of cultured tilapia, 16±0.20 g Oreochromis niloticus was used as the research object, the effects of different feed rates on tilapia growth and water quality indicators were explored. Biolog-ECO method was used to detect the utilization of 31 carbon sources by microorganisms in culture water samples, to study the differences of microbial metabolic diversity under different feeding rates. The results showed that the tilapia with 4% feeding rate had the lowest feed coefficient and relatively high feed utilization rate; high feeding rate had a relatively great impact on water quality, and different feeding rates had an impact on microbial metabolic diversity in aquaculture water; the Shannon index of 4% feeding rate was relatively high, and there were more kinds of microorganisms in water; Pearson correlation analysis showed that COD, TN, TP, NH₃-N had strong positive correlations (P<0.05) with water microbial metabolic diversity metabolism of β-methyl-D-glucoside, glucose-1-phosphate, glycyl-L-glutamic acid. In the process of tilapia culture, considering both ecological and economic benefits, we should feed the tilapia with proper feeding rates, the feeding rate with the initial tilapia size of about 16g is around 4%.

This experiment was conducted to evaluate the effects of digestible crude protein (DCP) and lipid (DL) levels on growth performance, metabolism of energy substances and antioxidant capacity of juvenile GIFI Tilapia (Oreochromis niloticus), and thereby to determine the optimal rate of digestible crude protein to digestible energy (DCP/DE). Juvenile fish with an initial average body weight of 2 g were fed 12 experimental diets with different nitrogen to energy ratios prepared with different DCP levels (22%, 24%, 26%, 28%) and DL levels (3%, 5%, 7%) for 10 weeks. The results showed as follows: with the increasing level of DCP and DL, the body weight gain (WG) and specific growth rate (SGR) of fish were significantly increased, but there was no significant difference between the 5%DL and the 7%DL group, and the protein efficiency showed a gradually decreasing trend. The WG and SGR of fish in the DCP26DL5 group were not significantly different from those in the highest DCP26DL7 group. The pepsin activity in DCP26DL5 group was significantly higher than that in DCP28DL3 group. The serum AST activity in DCP26DL5 group was the lowest. The TC and LDL-C content in DCP26DL5 group were significantly lower than those in DCP22DL7 group, and there was no significant change in blood glucose level among all groups. The antioxidant function of fish body was significantly increased. The SOD activity in liver of DCP26DL5 group was significantly higher than that in DCP22DL3 group. Findings reveal that high dietary DCP level will reduce protein efficiency, and high DL level will cause plateauing period of growth performance. The suitable level of DCP for juvenile tilapia is 26%, and the level of lipid is 5%. The optimal DCP/DE is 19.18 mg/KJ.

To study the influence of the floating bed culture of Jussiaea stipulacea (0, 5% planting area) on the pollutants in the culture pond of red tilapia (Oreochromis mossambicus× O. niloticus), the water quality indexes, such as COD_Mn, Chl.a, TN, NH₃-N, NO₂^--N, NO₃^--N, TP and PO₄^3--P, were determined. The results showed that compared with the control group, J. stipulacea could significantly reduce the contents of Chla, NH₃-N, NO₂^--N, as well as the contents of COD_Mn, TP, TN and NO₃^--N in the culture ponds of red tilapia. The average removal rate of NO₃^--N and NO₂^--N was more than 50%, but the removal effect on phosphorus was unsatisfactory.

By adding Chlorella to tilapia aquaculture water, this study aims to explore the optimal concentration of Chlorella for the degradation of N and P and the regulation of microbial community in aquaculture water. Control group (NC), low concentration group (LC), middle concentration group (MC) and high concentration group (HC) were set to explore the effects of different concentrations of Chlorella on reducing the concentration of N and P in tilapia aquaculture water. The 16S rRNA high-throughput sequencing technology was used to analyze bacteria community structure changes of aquaculture water body. Compared with other treatment groups, N and P nutrition of water body in HC group decreased, and the degradation rate of nitrogen in three forms was NH₄⁺-N>NO₃^--N>NO₂^--N. Compared with NC group, the microbial diversity of MC and HC group decreased. The relative abundance of Proteobacteria in each treatment group increased, while that of Bacteroidetes decreased, and the relative abundance of Bacteroidetes in HC group was the highest, the community richness was significantly correlated with the content of NH₄⁺-N. In summary, Chlorella can absorb N and P nutrition from aquaculture water, regulate aquaculture water microbial community structure, and improve aquaculture water quality. The study could provide a theoretical basis for aquaculture production practice.

China's fresh aquatic products market is growing rapidly, but the geographical difference between production and sales is obvious, and long-distance transportation demand is significant. The sedative can inhibit the body's metabolism and slow down the stress response of fresh aquatic products. Sedatives have been used in the transportation, breeding and surgery of aquatic products to increase the survival rate of aquatic products. However, the residual problems that may be caused by the widespread use of sedatives in aquatic products have attracted the attention of researchers at home and abroad. In this paper, the research progress of the detection technology of sedative residues in aquatic products was summarized, in order to provide reference for the follow-up research. This paper introduced the types and usage regulations of sedatives in aquatic products, and analyzed the research progress of sedatives in aquatic products in the past 10 years. The progress of sample preparation methods, HPLC detection methods, HPLC-MS/MS, and GC-MS/MS in the detection of sedative residues in aquatic products were reviewed, and the application prospects of the technologies were discussed. On the basis of the current study, more in-depth research should be carried out on the new simple and efficient sample preparation methods in the future to provide technical support for the supervision of sedatives in aquatic products.

From the perspective of supply and demand, this paper analyzed the current status, characteristics, existing problems and future development trends of the tilapia industry. The development of tilapia supply and demand is characterized by a high concentration of supply and scattered domestic consumption; products are mainly supplied to the international market and highly dependent on foreign countries; demanding countries are diversified and trade volume is greatly affected by the US market. China's tilapia demand has changed significantly, especially due to the uncertainty of the US market, which has caused a partial surplus of tilapia supply. It is expected that the demand for tilapia would decline significantly in the future, but this decline will be alleviated after the impact of COVID-19 and the demand will continue to grow. Due to market uncertainty and other reasons, China’s tilapia supply will increase at a low level, or even decrease.

To provide a scientific basis for the nutritional evaluation of Acrossocheilius parallens muscle, the contents of routine nutrition components, fatty acids and amino acids in muscle were determined and analyzed by biochemical method. The results showed that the contents of water, crude protein, crude fat and crude ash in A.parallens muscle were (77.20±0.42)%, (19.70±0.22)%, (3.25±0.07)% and (1.30±0.01)%, respectively. There were 21 kinds of fatty acids in the muscle, including 8 saturated fatty acids (SFA) and 13 unsaturated fatty acids (UFA). The proportion of UFA and essential fatty acid (EFA) was 68.07% and 21.76%, respectively. There were 17 kinds of amino acids in the muscle, including 7 essential amino acids (EAA), 2 semi-essential amino acids (HEAA) and 8 non-essential amino acids (NEAA). EAA and umami amino acid (UAA) accounted for 40.85% and 37.55% of the total amino acids, respectively. The amino acid composition of A.parallens muscle was well balanced. The amino acid score (AAS) of A.parallens muscle was more than 1 except Valine, the chemical score (CS) was more than 0.5, and the essential amino acid index (EAAI) was 86.19, indicating that the quality of protein was good. To sum up, the high nutritional value of the A.parallens is a kind of high-quality economic freshwater fish with high development value.

The global supply chain of aquatic product has been influenced to some extent amid COVID-19 pandemic. This paper analyzed the current situation of aquatic product supply chain both at home and abroad, the problems found in the chain and the adopted response strategies, aiming to ensure the safety of imported aquatic products and the stable operation of the supply chain in China. Affected by COVID-19 pandemic, global trade of aquatic products has been slightly reduced, both supplying and trading venues are at risk of virus infection. In response to the crises, FAO and China have taken a number of measures, such as issuing relevant business guidelines, using digitalization to promote electronic trade, supervising personnel management, strengthening port quarantine, and improving market sales models. On this basis, this paper suggested building product traceability system, strengthening the epidemic prevention intensity and quality control of key products, innovating consumption and service patterns, and establishing a series of emergency response mechanisms to ensure the safety of China’s imported aquatic products.

To analyze the competitive advantage of China’s characteristic freshwater fish industry, this paper carries out an analysis in 31 provinces and regions based on Michael Porter's diamond model. This paper also constructed the competitiveness evaluation index system of characteristic freshwater fish industry, mainly focused on four main export species of Oreochromis niloticus, Anguillas, Ictalurus punctatus and Acipenser sturio, so as to explore the competitive advantage and international competitiveness of the industry. The results show that: (1) China’s characteristic freshwater fish industry has obvious resource endowment advantages in production competitiveness factors, in terms of market demand factors, the consumption of characteristic freshwater fish is increasing day by day; in terms of related industries, market structure and competition, the technical content and economic added value of processed products of characteristic freshwater fish needs to be improved, the industrialized application of specialized feed for characteristic freshwater fish is not enough, and the number of large-scale enterprises needs to be increased; in terms of opportunities and government policies, a green and healthy ecological breeding system has been gradually established; (2) the resource endowment coefficient of characteristic freshwater fish is always above 1.0, which has obvious advantages of resource endowment; the international market share of China’s characteristic freshwater fish is 73.22%, the trade competitiveness index is close to 1; the revealed comparative advantage coefficients of tilapia and eel are both greater than 6, indicating that China’s characteristic freshwater fish products have obvious competitive advantages in the domestic and foreign markets.

Rice-fish farming, with small investment, quick effect, low risk and high profit, is an important means of poverty alleviation through the development of green industry. The authors analyzed rice-fish farming modes in Hunan, such as government predominance type of Chenzhou Ctiy, market-oriented type of Nanxian County, and government plus market type of Chenxi County, for poverty alleviation. It is suggested that the long-term plan, mechanism of industrialization and performance evaluation, construction of infrastructural facilities, research on policy of rice-fish farming should be enhanced for poverty alleviation through industrial development.

To verify the practical culturing effect of a previously designed circulating water treatment system based on heterotopic pond restoration technology, a large-scale multi-species saturating culture experiment was carried out for 3 years. The effects of the system on water quality control was evaluated by measuring the total nitrogen (TN), total phosphorus (TP), chemical oxygen consumption (COD_Mn) and chlorophyll (Chla) in a common freshwater fish culturing pond. The results showed that in the early stage of the experiment, the total nitrogen level (TP) of the circulating water of the pond reached Class III of the Environmental Quality Standards for Surface Water (GB 3838—2002), and the total phosphorus level (TN) reached Class III to V. The average removal rate of TP, TN, COD_Mn and Chla was 40.13%, 45.02%, 43.37% and 86.6%, respectively. The removal efficiency of the system was significant. In the late stage of the experiment, with the continuous increase of the feed input, although the efficiency of the circulating system was greatly improved, the data of each index were still higher than expected. This experiment provides a new idea for the treatment of large-scale aquaculture water by circulating water in freshwater ponds.

To select the suitable pond culture mode for juvenile Alosa sapidissima, juvenile Alosa sapidissima was used as material, and the digestive enzyme activities of juvenile Alosa sapidissima cultured in the outdoor pond and shaded pond were compared. The results showed that: at the earlier culture stage, the activity of amylase in the visceral mass of juvenile Alosa sapidissima cultured in outdoor pond was higher than that of shaded pond; in 43 days and 57 days, the activities of pepsin, trypsin and lipase in the visceral mass of juvenile Alosa sapidissima cultured in outdoor pond were higher than those of shaded pond, but in 15 days and 29 days, the situation was reverse. At the later culture stage, the activities of pepsin and trypsin in liver and stomach of juvenile Alosa sapidissima cultured in shaded pond were higher than those of outdoor pond in 79 days, 106 days and 120 days; and the activities of amylase and lipase in liver and stomach of juvenile Alosa sapidissima cultured in shaded pond were also higher than those of outdoor pond at 106 days and 120 days; the activities of pepsin and trypsin in the liver and stomach of juvenile Alosa sapidissima cultured in shaded pond were lower than those of outdoor pond in 92 days. Therefore, in the season of high temperature, the juvenile Alosa sapidissima should be cultured in outdoor pond directly.

The paper aims to study the large-scale freshwater fish farming and industrial space optimization. Based on the standard ellipse model, the grass carp with the largest output of freshwater fish was selected as the research object. The spatial distribution pattern (agglomeration degree, gravity center, scope and direction), evolution characteristics and influencing factors of grass carp industry development were analyzed based on the scale of grass carp industry in 31 provincial-level administrative regions of China from 2006 to 2016. The spatial agglomeration of grass carp industry in China shows a trend of discrete agglomeration. The steady increase of output in the upper and middle reaches of the Yangtze River basin and the enlargement of grass carp culture in arid and semi-arid areas in northwest China have promoted the shift of the standard ellipse of grass carp industry to the west and north. The spatial distribution of grass carp industry development presents decentralized agglomeration. Grass carp farming gradually changes from extensive farming to fine farming. The spatial transmission mechanism of grass carp industry development is from the central and eastern regions to the west and north. This is mainly due to the good environmental adaptability of grass carp, relatively low cost in the central and western regions and the expansion effect of the market.

The study was conducted to investigate the variation of fish body composition, digestive enzyme activity and RNA/DNA ratio of Schizothorax wangchiachii juveniles after starvation and refeeding, to provide a scientific basis for artificial culture. S. wangchiachii juveniles were used as materials. Crude protein, crude fat, moisture and crude ash of the fish body were measured by Kjeldahl method, Soxhlet extraction method, Thermostatic and weightless drying method and muffle furnace burning method, respectively. The mineral elements were measured using inductively coupled plasma atomic emission spectrometry, the digestive enzyme activity and the DNA/RNA ratio were measured by spectrophotometry. The results showed that the crude fat content of juveniles declined to the minimum of 5.01% after 5-day starvation. The crude protein content reduced to the minimum of 13.61% after 2-day starvation. The moisture and ash content, Ca and P content all increased after starvation. The contents of K, Na, Mg and Fe increased to the peak after 9-day starvation, and then decreased with starvation continued. The trypsin and lipase activity of liver-pancreas increased firstly, followed by a short decline, and then the activity finally increased. The amylase activities declined throughout the starvation time. The muscle’s DNA content increased, while RNA content and RNA/DNA ratio decreased. After refeeding, The Fe contents in group S15 and S25 were lower than those of the control group. The amylase activities of liver-pancreas recovered to normal level in all the groups. However, the liver-pancreas lipase activities of group S15 and S25 were significantly lower than that of the control group (P<0.05). The RNA content and RNA/DNA in muscle were extremely and significantly decreased in group S15 and S25 (P<0.01). The biochemical indexes of S. wangchiachii juveniles were not affected by 9-day starvation (P>0.05), and no significant difference with control was found after refeeding (P>0.05). The starvation time should not exceed 9 days.

Marine fish have high nutritional value and is popular with the people, and the market is short of supply. China is the largest mariculture country in the world, and has accumulated rich experience in the exploration and practice of marine fish farming. Based on the data of China Fisheries Yearbook and FishstatJ database from Food and Agriculture Organization of the United Nations, the author combines qualitative & quantitative methods to sort out the development of mariculture industry since the founding of the P. R. China, including species structure, regional distribution characteristics, aquaculture models and cost-benefit indicators. The author also analyzes the paths of technological change of marine fish farming, disease prevention and control, nutritional needs and diet formulation, fine management and aquaculture engineering facilities, thus to reveal the evolution rule and provide reference for formulating the sustainable development strategy of marine fish farming.

The paper aims to study the effects of various salinities on liver histomorphology, non-specific immune and digestive enzymes activities in juvenile Chum salmon (Oncorhynchus keta). The Chum salmon was cultured in salinities 0‰, 8‰, 16‰ and 24‰ for 42 days,respectively, we measured the non-specific immune enzyme and digestive enzyme activities by using the liver and digestive tract, and observed the liver structure change under different salinities. The results showed that: the trend of superoxide dismutase, glutathione peroxidase and catalase activities in the liver of juvenile Chum salmon increased first and then decreased with the increase of salinity, but the enzyme activity peaks were different; the alkaline phosphatase activity increased first and then decreased with the increase of salinity, but different salinity treatment groups had no significant effects on acid phosphatase activity (P>0.05); different salinities had complicated effects on various digestive enzymes’ activities in the digestive tract and there was no overall effect between various digestive enzymes; histological observation showed that the liver structure of the salinity group 0‰, 8‰, and 16‰ was normal, while the salinity group 24‰ showed a certain degree of lesions. It is speculated that 8‰-16‰ is the optimal salinity for juvenile Chum salmon with the body weight about 1 g during the catadromous migration period.

The paper aims to provide a scientific basis for fertilization management of fish culture in paddy fields. Taking a new hybrid rice variety ‘Nei6You106’ as material, we studied the coupling effects of fish-nitrogen-density on soil fertility, rice yield and nutrient uptake and accumulation in paddy fields under 3 fish-nitrogen treatments (CK: no fish + no nitrogen application, F: fish + no nitrogen application, FN: fish + 150 kg/hm ² nitrogen application) and 4 seedling densities. The results showed that: the organic matters significantly increased, nitrogen maintained balance, phosphorus and potassium decreased significantly after fish culture in paddy fields; the overall trends of rice yield, over ground dry matter and accumulation of nitrogen, phosphorus and potassium under fish-nitrogen treatments were FN>F>CK, FN and F significantly increased rice yield by 22.98% and 13.43% compared with that of CK, respectively; there was no significant difference in rice yield in the range of 90000-225000 hills/hm ², and the effects of dry matter and nitrogen accumulation increased with the increase of density; the nitrogen, phosphorus and potassium requirements of above ground plants per 1000 kg of rice were 10.24-16.74, 1.31-2.72, 34.38-56.49 kg/hm ², respectively. Therefore, nitrogen fertilizer should be controlled, and phosphorus and potassium fertilizer should be increased in fertilizer management of medium-high yield fish culture paddy fields.

In this paper, the regional structure, market structure and market price of sturgeon caviar export of China are analyzed. The main exporting countries of sturgeon caviar in the world are estimated by using three indicators: international market share, dominant comparative advantage index and trade advantage index. It is found that the export areas and export structures of sturgeon caviar of China are relatively concentrated and have strong international competitiveness. The export price is declining year by year, and the overall competitiveness still has a lot of room to rise. On the basis of the previous analysis, suggestions on enhancing the competitiveness are put forward, such as accelerating the construction of aquatic products processing and export base, strengthening brand building and developing diversified export market.

To further promote the in-depth development of the research on artificial fish nest technology and the popularization and application of fishery resources proliferation technology, we summarize the development status of artificial fish nest breeding technology at home and abroad, sum up the research examples of different types of artificial fish nests in fishery resources proliferation, and expound the effects of artificial fish nest breeding technology on increasing yield and efficiency. In addition, we summarize the types, structures and materials of artificial fish nests, put forward the requirements of site selection, construction and management of artificial fish nests, discuss the development prospect of artificial fish nest, and point out the key research direction of artificial fish nest technology.

To improve the water quality, the fishery multiplication and the restoration of ecological environment, the application of EM bacteria has attracted extensive attention and become a research hotspot in recent years. This study systematically reviewed the definition and source of EM bacteria, the effect and mechanism of EM bacteria in aquaculture in recent decades, and elaborated the factors affecting the effect of EM bacteria. It is found that: EM bacteria have significant effects on regulating microbial ecological structure, reducing harmful substances in water environment, improving immunity, gaining weight and increasing yield; however, the basic theoretical research of EM bacteria technology is still relatively weak, and there are still deficiencies in the production technology and application process. Therefore, in the future, it is necessary to improve production technology, establish and improve screening system, and develop new fields of research and application of EM bacteria in aquaculture, so as to create greater economic value for aquaculture and provide the possibility for sustainable aquaculture.

To study the effect and mechanism of “using aquaculture to curb alkali saline-area” model on the saline-alkali land, the saline-alkali land in Jingtai County was used as test field, the solodization effect of aquaculture technology on sandy saline-alkali soil and loam saline-alkali soil was compared. The effects of aquaculture on saline and alkali migration were studied by regularly monitoring and analyzing the changes of water quality parameters in different types of soil and water before and after fish culture. The results showed that the aquaculture model could improve the soil environment of saline and alkaline areas to some extent, and the control effect on sandy soil was better than that on loam soil. In addition, the ammonia nitrogen produced during the cultivation did not show an upward trend, which indicated that it did not cause secondary pollution to the local area. The results of this study provided theoretical and technical support for the application and promotion of “using aquaculture to curb alkali saline-area” model in northwest China.