Present status of aquaculture and the challenge of bacterial diseases in freshwater farmed fish in Tanzania;A call for sustainable strategies

Aquaculture provides significant contributions to household food security,as the capture of wild fish from lakes,dams,and oceans do not meet the current demand for animal protein in Tanzania.Sustainable aquaculture requires well-established regulatory systems and extension services for good pond management practices and maintaining fish health by fish farmers.Fish farming is practiced widely in Tanzania,from small-to large-scale ponds and these farming systems are moving from extensive normal operations(low input demand)to intensive farming(high input demand).However,the industry is largely still operating at a subsistence level with low production.Bacterial infections have been occurring in these fish farms and will continue to be an issue of concern into the future.This review highlights the current challenges,successes,and prospects towards a sustainable aquaculture industry in Tanzania,including:limited extension services mirroring the limited knowledge by farmers regarding pond management practices;the inadequacy of funds to carry out fish disease research or implement a surveillance system;little expertise in fish disease diagnosis and treatment;and poor management options.To minimize disease outbreaks and optimize production in the future,we suggest a strengthening of extension services,augmented with on-farm knowledge transfer.Emphasis should be on pond management practices and fish disease management;the creation of a well-functioning fish disease surveillance system;and strengthening collaborative research on aquaculture between the government research institutions and academia.Establishing small cooperative fish farmer groups within the Aquaculture Association of Tanzania(AAT)for easy access to information is also recommended.

Enhanced Water Quality Control Based on Predictive Optimization for Smart Fish Farming

The requirement for high-quality seafood is a global challenge in today’s world due to climate change and natural resource limitations.Internet of Things(IoT)based Modern fish farming systems can significantly optimize seafood production by minimizing resource utilization and improving healthy fish production.This objective requires intensive monitoring,prediction,and control by optimizing leading factors that impact fish growth,including temperature,the potential of hydrogen(pH),water level,and feeding rate.This paper proposes the IoT based predictive optimization approach for efficient control and energy utilization in smart fish farming.The proposed fish farm control mechanism has a predictive optimization to deal with water quality control and efficient energy consumption problems.Fish farm indoor and outdoor values are applied to predict the water quality parameters,whereas a novel objective function is proposed to achieve an optimal fish growth environment based on predicted parameters.Fuzzy logic control is utilized to calculate control parameters for IoT actuators based on predictive optimal water quality parameters by minimizing energy consumption.To evaluate the efficiency of the proposed system,the overall approach has been deployed to the fish tank as a case study,and a number of experiments have been carried out.The results show that the predictive optimization module allowed the water quality parameters to be maintained at the optimal level with nearly 30%of energy efficiency at the maximum actuator control rate compared with other control levels.

Seasonal Variations in Serological Profiles and Growth Status of Farmed and Wild Clarias gariepinus （Burchell, 1822） Obtained from Asaba, Nigeria

Seasonal variations in serological profiles and growth status of farmed and wild Clarias gariepinus were investigated. Serological profiles of Clarias gariepinus can be an effective tool for proper monitoring of stress induced by management practices in intensive fish culture, which may elicit devastating effect on fish. Spectrophotometry procedures were used to analyze serum parameters of Clarias gariepinus. No different seasonal patterns were observed for mean values of albumin, total protein, urea, cholesterol, glucose and alanine amino-transferase. However, aspartate amino-transferase showed different seasonal pattern. Levels of cholesterol and alanine amino-transferase were highly significant in farmed and wild fish, separately. Juvenile fish had high level of urea irrespective of season. Seasonal variations in water quality parameters were observed except for pH which had no seasonal pattern. The growth exponential shows b-values between -0.048 and 7.434 for Clarias gariepinus. Adult female and juvenile fish from the wild had the highest b-value and the least b-value, separately. In this study, b-values were higher in the wild fish than the farmed fish. The condition factor for Clarias gariepinus ranged from 0.422 to 0.698, and was observed to be high in juvenile fish. With a condition factor less than 1, fish may not be doing well, probably due to environmental stress. Some serological parameters varied according to season and environment of fish. Thus, serological profile of fish is an effective and sensitive tool to monitor fish response to stress factors in the environment.

Contribution of Garcinia kola to the Productivity and Economic Profitability of the Community Agricultural Area of Kedougou: Financial and Comparative Analysis of Production Factors

Inland fishing predominates in the Kedougou region, which has no coastline. This type of fishing does not yet meet the local population’s demand for fish products. In response to this concern, a Community Agricultural Estate housing an integrated fish farm was set up in the commune of Bandafassi, in the village of Itato. Since its creation, this production unit has been faced with the problem of sourcing high-quality, low-cost, monosex male Oreochromis niloticus fry. In order to overcome this constraint, the present research focuses on the contribution of Garcinia kola to the productivity and economic profitability of the Itato farm. The aim of the research is to assess fish production in the experimental set-up and the production costs of tilapia in a controlled environment. The comparative study of the various production factors shows disparities only in the input factor, where scenarios 2 and 3 use additional products. These are 17-α-methytestosterone for scenario 2 and Garcinia kola for scenario 3. These products significantly interfere with fish production, with a fairly high mortality rate for scenario 2 (25% for two production cycles/ cohort2 (B5, B6, B7 and B8) treated with 17-α-methytestosterone). As for scenarios 1 and 3, mortalities are 5% with or without recourse to additional products (G. kola). In addition, average fish production for the three (03) scenarios is estimated at 28687.5 kg/2 cycles. It varies from one scenario to another, i.e. 30937.5 kg/2 cycles for scenarios 1 and 3 and 24187.5 kg/2 cycles for scenario 2. It is therefore higher in scenarios 1 and 3 than in scenario 2. This difference is due to the fairly large losses of individuals in scenario 2. Furthermore, the analysis of the profit and loss accounts for tilapia production varies from one scenario to another depending on the type of farm: 476 Franc CFA for scenario 1, 610 Franc CFA for scenario 2 and 472 Franc CFA for scenario 3 (F CFA = franc of the French Colonies of Africa). The Average operating income for all the fish farming units is 34,726,142 Franc CFA. The highest (41,638,075 Franc CFA) and lowest (29,281,075 Franc CFA) ERs were observed in scenarios 3 and 2 respectively. It was 33,259,275 Franc CFA for scenario 1. The difference between the NERs of the three scenarios is more or less significant in terms of results. The operating result (OR) is positive in all 3 scenarios in our study. However, the scenario 3 system generates a higher rate of return (the ratio between an income and the capital employed to obtain that income) (74%) than that generated by the scenario 1 system (69%). As for the scenario 2 system, it generates a lower financial return than the two previous systems (67%). Above all, this work made it possible to construct an approach that would make it possible to answer such a question by relying successively on various methods: a typology, according to the production factors involved in the operation of the Community Agricultural Estate fish farm.

Identification of Aquaculture-Derived Organic Matter in the Sediment Associated with Coastal Fish Farming by Stable Carbon and Nitrogen Isotopes

Abstract： Stable carbon and nitrogen isotope analysis was used to identify the aquaculture-derived organic matter in the sediment in and around a coastal fish farm in China. Results showed that mean δ13C value in fish farm area （within 1 O0 m from the edge of cages） and control area （500 m from the edge of cages） was -17.72±1.29/oo and -12.73± 0.380/00, respectively. Mean δ15N value of fish farm area and control area was 6.44 4±0.2%0 and 5.61 4±0.2%0, respectively. The sediment in the fish farm area was characterized by high waste food （47.70%） and faeces （27.71%） ratio, as the distance from the fish cages increased, aquaculture-derived organic matter decreased expontially （y = 97.167e-0.0074x, R2= 0.8481）. The spatial extent of waste dispersal extended to an area up to 400 m.

The Occurrence of Bacteria of the Genus Aeromonas spp.in Oreochromis niloticus(Tilapia)and in the Water of Amateur Sport Fish Ponds and Sensitiveness to Antimicrobials

Since amateur fishing in fishponds has been on the increase in Brazil, there is a great concern on the microbiological quality of fish. One hundred and thirty-eight samples were collected during the dry and rainy periods in ten fish farms. Aeromonas spp. counts and tests for sensitiveness to antimicrobials were performed, coupled to the physical and chemical analyses of water. Tests revealed that 70% of samples were contaminated by Aeromonas spp., with water averaging 2.92 Log CFU/100 mL during the rainy period and 3.16 Log CFU/100 mL during the dry one. Fish contaminated by Aeromonas spp. averaged 2.58 Log CFU/100 mL during the rainy period and 3.53 Log CFU/100 mL during the dry one. Aeromonas spp. samples were multi-resistant to 2 or 8 antimicrobials in 62.5% of the samples. Ampicillin was the antimicrobial with the highest resistance percentage rate. Results showed that fish bred in amateur fish farms constituted a health risk for the population.

Bio-Filtration Technologies for Filtering Ammonia in Fish Tank Effluent for Reuse--A Review

Peri-urban fish farms with limited access to open natural water bodies draw fresh water from urban water supply and dug wells,which is unreliable and costly.Reuse of fish pond effluent is also limited by high ammonia concentration(>0.3 mg/L)that renders water toxic and is stressful to fish.Despite the existence of several fish effluent treatment methods,not all may be appropriate for a particular location.This review article therefore examines the various fish effluent treatment methods to aid selection of the most suitable one(s)for peri-urban areas.The key parameters considered in their comparison were:initial,operational and maintenance costs;ammonia removal efficiency;energy consumption and land requirement.The effluent treatment methods are both conventional and non-conventional.Despite a slight higher treatment efficiency and less space requirement by conventional methods,they mainly require reliable power supply for continuous running,highly skilled labor for operation and maintenance leading to high operational costs.In addition,their investment costs are higher than non-conventional methods,hence not widely applied in developing countries and majority have broken down.On the other hand,non-conventional methods such as constructed wetlands are widely in use for treating effluent mainly due to their cost effectiveness and no or little energy requirement.Constructed wetlands were found most suitable bio-filtration system for treating fish effluent because they are cost effective,require less skilled labor and still have better effluent treatment though space required is slightly more.Vegetables(lettuce,collards,etc.)have potential to grow in constructed wetlands thus form vegetable-based bio-filtration units which serve not only as bio-filters but also provide additional sources of nutrition and income.This review indicated limited information on the appropriate size and performance of vegetable-based bio-filtration unit utilizing indigenous vegetables and recommended further research to explore the idea.

Characteristics, Constraints and Perspectives of the Fish Farming in Burundi

The fish farming was introduced in Burundi in about 1950s. Actually, several fish ponds were abandoned and many others were still unproductive. This study aims to present current state and perspectives of the fish farming for its real contribution to the socio-economic development. The results presented are compilation of physical and chemical parameters series measured in fish ponds and inquiries led in 2010-2014 to the fish farmers in seven provinces （40% of the total area of the country）. Weak values of some physical and chemical parameters showed that the majority of ponds are badly maintained. Thus, the dissolved oxygen values varied between 0.2 mg/L and 3.5 mg/L. The high relinquishment rate of the fish fanning （between 40% and 67% according to the provinces） could be explained by many constraints： no centers of fish farming breeding for various fish species and no production center of complete foods with local sub-products. About 75% of fish famers confirmed that they have never benefited framing in fish fanning. In spite of the diverse constraints, Burundi has a dense rivers system with favorable physical and chemical parameters and many appropriate sites for the fish farming. Thus, the main suggestions concern the sector reorganization.

Effect of Socio-Economic Variables on Fish Production of Small Farmers in Tocantins State, Brazil

Fish farming is a strategic activity for both the economy and food security of the Tocantins state. Nowadays, there are about eighty small fish farmers in the region of Divin6polis in Tocantins state. The technological level of fish farmers is low and it was found that only 30% of farmers could ever get to the point of selling fish. Therefore, the objective of this paper is to investigate which socioeconomic factors have influence on the fact of fish farmers in the region of Divin6polis and in Tocantins state reach a level of efficiency in production enough that the fish can be good for sale in the local market. To estimate this relation the logit model was chosen, with methodology based on the empirical model used in Musaba and Namukwambi. Following the production of fish farms in the Western of Tocantins state, the collect of the data, during 2012, were conduct with interviews of 30 fish farms, visiting them in their homes and applying a questionnaire. Through the use of econometric models of probability for limited dependent variables, it was found that factors such as participation in federal programs to transfer income, total area of water and production in ponds are key factors in determining the likelihood of producer to sell fish.

Integration of Fish and Poultry Farming into Cropping Systems to Improve Production Yields

This study aims to evaluate and compare the fertilizing effects of fish-breeding water and river water combined or not with composted poultry manure on the growth and production of okra and lettuce crops. Thus, a sample of 2000 Nile tilapia Oreochromis niloticus fry and a sample of 100 Cobb 500 strain chicks were reared and monitored for six months and fifteen days. Poultry manure and fish-breeding water were then collected and used to fertilize and water okra and lettuce crops. Two systems were used for the crops (okra and lettuce) tested in an elementary plot design with replicates for each treatment (T1: fish-breeding water alone;T2: river water alone;T3: fish-breeding water combined with manure;T4: river water combined with manure). Morphometric parameters and phenological traits of okra and lettuce crops as well as the total harvest weight and production yield were evaluated and compared between treatments. The results reveal better growth and higher yields (0.67 kg/m2 vs. 0.45 kg/m2) of okra crops that received treatment T1 compared to T2. The best growth and yields of lettuce were obtained with treatments T3 (3.34 kg/m2) and T1 (1.89 kg/m2) compared to T4 (1.23 kg/m2) and T2 (1.20 kg/m2). These results show that fish-breeding water combined with poultry manure can boost okra and lettuce production and would be a real asset to stimulate local agricultural development. Thus, the adoption of such an agro-ecological approach integrating fish farming and animal husbandry could increase local production and provide food of good nutritional quality.

Monitoring Trace Metals in Some Cultured Freshwater Fish Species in Saudi Arabia

Three species of freshwater fishes, Oreochromis niloticus, Clarias lazera and Cyprinus carpio, were collected in marketing size from some fish farms in Al-Kharj region, Riyadh area, Saudi Arabia and examined throughout the year 2012 for the following trace metals contents： chromium （Cr）, lead （Pb）, cobalt （Co）, nickel （Ni）, copper （Cu）, zinc （Zn）, iron （Fe） and cadmium （Cd）. The results showed no detection of Cd in all examined species, however, the mean values of other tested metals were within the standard permissible levels except for Pb which showed higher mean levels ranged from 2.05 ± 0.65 mg/kg to 5.30 ± 0.60 mg/kg in O. niloticus, 0.15 ± 0.13 mg/kg to 6.40 ± 0.10 mg/kg in C. lazera and 1.7 ± 0.20 mg/kg in C. carpio compared to the maximum permissible limits recorded by Saudi Arabia Standards Organization （SASO） for fish and shellfish. Consequently, from the public health point of view, efficient routine examination of cultured fishes to control trace metals during culture processes and before marketing is recommended.

The Influence of Land Use and Fish Farming on the Contents of Ca²⁺, Mg²⁺, K⁺and Na⁺in Pond and Reservoir Ecosystems in an Agricultural Small Watershed, China

It is not understood well that how the effects of land use and fish farming on the contents of alkali metals (Ca2+, Mg2+, K+ and Na+) in small water bodies of pond and reservoir ecosystems at the watershed scale. In this study, the concentrations of Ca2+, Mg2+, K+ and Na+ in water bodies were measured for 103 ponds and reservoirs used as fish farming or surrounded by different agricultural land use types in the subtropical hilly watershed of Jinjing (105 km2), China. The two important environmental factors of fishing farming and agricultural land use influenced the spatial variation the contents of alkali metals. The ponds and reservoirs in residential area had significantly higher concentrations of Ca2+ and Na+ than those with other land use types, reflecting the influence of domestic wastewater. Compared with those of natural ponds with non-fish farming, no significant increase of alkali metal contents occurred in fish farming ponds, due to the regular cleaning of ponds by farmers. However, the effect of fish culture on alkali metal contents was still supported indirectly by the fact that the alkali metal contents significantly correlated with nitrate contents in fish farming ponds and but high related with that of DIP in natural ponds. The suitability assessment for irrigation on the pond water indicated that almost all of ponds were suitable for irrigation except some ponds surrounded by residential area and tea plantation. Generally, our results demonstrated that fish farming and agricultural land use affected the contents of alkali metals in ponds and reservoirs. The agricultural water irrigation would be with caution from the ponds with tea plantation and residential area in the subtropical hilly watershed.

Artificial reproduction of neotropical fish:Extrusion or natural spawning?

In captive conditions, most neotropical migratory species do not have the necessary incentive to complete gonadal maturation and spawning, which require induction techniques, usually with the use of hormones. Numerous studies have therefore focused on finding an effective hormonal treatment to induce reproduction for each species. A standard treatment was successfully developed for most of these species, which consists of two doses of Carp Pituitary Extract (CPE), totaling 5.5 mgCPE/kg of fish. However, the best strategy for the subsequent fertilization of gametes is still unclear. This study was conducted with five species of commercial interest that do not reproduce naturally in captivity: pacu Piaractus mesopotamicus, piracanjuba Brycon orbignyanus, curimbatá Prochilodus lineatus, dourado Salminus brasiliensis and piau?u Leporinus macrocephalus. Ninety-nine broodstocks were used, consisting of males and females of the five species to compare two techniques for spawning and fertilization: extrusion followed by the dry method and natural spawning. All fish were induced with two hormone doses, i.e., 0.5 and 5.0 mgCPE/kg, and were subjected to one of the two types of fertilization. The results were compared using the fertilization rate, number of oocytes produced, relative fecundity and the broodstocks' survival rate on days following spawning. All species responded positively to spawning for extrusion, and only S. brasiliensis did not spawn through the natural spawning method. The natural spawning technique provided a higher fertilization rate of eggs and a greater broodstock survival rate (P S. brasiliensis. It was concluded that the natural spawning technique can increase the production of viable eggs and reduce the mortality of species during breeding, except for S. brasiliensis.

Fish Farming Boost

AFRICAN fish farmers are benefiting from improved livelihoods and a better food security status, thanks to the introduction of two strains of improved Nile tilapia in Egypt and Ghana. This follows 10 years of breeding research, culminating in the introduction of the Abbasa strain of the Nile tilapia （Oreochroml：s nlToticus） in Egypt. The species is indigenous to much of Africa. It grows 28 percent faster than most of the common varieties in Egypt, such as the Kafr El Shaikh strain. The second new tilapia Akosombo strain,

Problems and prospects of fish farming in the Chattogram Hill Tracts of Bangladesh:Community-based aquaculture might be a right choice

The study was carried out in Matiranga Upazila,Bandarban district,which is considered one of Bangladesh’s major hill tract regions.The study aimed to identify present farming conditions,prospects,and problems and suitable solutions to the problems of fish farming.Different participatory rapid appraisal tools such as focus group discussion,field visits,and farmers’interviews were used to collect relevant fish farming information in the study area.The polyculture method was the most practised aquaculture method.Among the selected farms,eleven fish species were identified as culture species.The transportation cost for seeds purchased from remote areas was high(11%of total seed cost).The average transportation-related mortality of fish fry and fingerlings was 7.2%and 2.8%.Feed cost was found as the major cost(58.4%)in aquaculture.Costs and revenue for fish production per decimal varied from BDT 311 to 3528 and BDT 23 to 1268.Utilization of vacant lake,youth and women engagement,integrated aquaculture,the desire of people to engage in aquaculture,and available human resources were found as significant prospects.The major problems identified were lack of hatchery,high feed cost,lack of stakeholder linkage,lack of capital for fish farming,and lack of proper knowledge,guidelines,and consultancy for fish culture.A community-based aquaculture model was proposed to overcome the present challenges and problems in the study area.The model may help to expand aquaculture and thus improve the livelihood and socio-economic status of the people of the hilly areas of Bangladesh.

Research Progress in the Application of Chinese Herbal Medicines in Aquaculture： A Review

Due to increasing safety concerns regarding human consumption of fish products, an increasing number of medicinal chemicals are prohibited from use in aquaculture. As a result, Chinese herbal medicines are being increasingly used, coining the use of the term ＂green medicine.＂ Research shows that Chinese herbal medicines have many beneficial effects on fish, including growth promotion, enhancement of disease resistance, and improvement in meat quality. Many effective ingredients have been discovered in Chinese herbal medicines, which function to promote feed intake, improve meat flavor, and increase digestive enzyme activity. They also regulate and participate in processes that improve the specific and non-specific immunity of fish; however, the composition of Chinese herbal medicines is very complex and it is often difficult to identify the effective ingredients. This article reviews the latest research and application progress in Chinese herbal medicines regarding growth and feed utilization, immunity and disease resistance, and the meat quality of cultured fish. It also discusses research on the chemical constituents of classical Chinese medicinal herbs and problems with the application of Chinese herbal medicines in fish culture. This article concludes by proposing that future studies on Chinese herbal medicines should focus on how to cheaply refine and extract the effective ingredients in classical Chinese medicinal herbs, as well as how to use them efficiently in aquaculture.

The Origin of Flooded Rice Cultivation

Rice cultivation has long been considered to have originated from seeding of annual types of wild rice somewhere in subtropics, tropics or in the Yangtze River basin. That idea, however, contains a fatally weak point, when we consider the tremendous difficulty for primitive human to seed any cereal crop in the warm and humid climate, where weed thrives all year round, instead of the accepted theory, we have to see a reality that vegetative propagation of edible plants is a dominant form of agriculture in such regions. The possibility is discussed that Job＇s tears and rice, two cereal crops unique to the region, might have been developed via vegetative propagation to obtain materials for medicine or herb tea in backyard gardens prior to cereal production. This idea is supported by the fact that rice in temperate regions is still perennial in its growth habit and that such backyard gardens with transplanted taro can still be seen from Yunnan Province of China to Laos. Thanks to detailed survey of wild rice throughout China for 1970-1980, it is now confirmed that a set of clones of wild rice exist in shallow swamps in Jiangxi Province, an area with severe winter cold. In early summer ancient farmers may have divided the sprouting buds and spread them by transplanting into flooded shallow marsh. Such way of propagation might have faster improved less productive rice through a better genetic potential for response to human interference than quick fixation in seed propagation, because vegetative parts are heterogeneous. Obviously, such a primitive manner of rice cultivation did include the essential parts of rice farming, i.e., nursery bed, transplanting in flooded field of shallow marsh like. Transfer from the primitive nursery to true nursery by seed may have later allowed rice cultivation to be extended to northern regions. In thus devised flooded cultivation there were a series of unique advantages, i.e.; continuous cropping of rice in a same plot, no soil erosion, slow decline of soil fertility, availability of minerals, and resulting in high yield per unit area, which have collectively attained the highly productive cereal cultivation in the warm and humid region. Rice cultivation in marsh is also favorable to raise fish culture, both of which constituted a nutritionally balanced base. Development of irrigation technology to construct flooded farms gave strong bases for stable rice-cultivating society, which in the end formulated the rise of ancient kingdoms of Yue and Wu in China in BC 6th -5th centuries. They were direct descendents of those people who had developed the unique rice cultivation from the era of Hemudu culture, which is dated back to 5 000 BC. Their movement to the south is considered to have established rice-cultivating communities in South China and Southeast Asia, while to the north it transferred the rice-based technology to ancient Korea and Japan and had established there a base for a civilized society.

The seasonal dynamics of geochemical characteristics of sediments in the impact zone of the fish farm(Lake Ladoga,Russia)

This study focuses on the analysis of seasonal dynamics of physicochemical parameters(pH and Eh)and organic matter content in the sediments accumulated within the impact zone of the cage trout farm(Lake Ladoga,Russia).The Ladoga is the largest lake in Europe and there are more than 20 fish farms located in the northern part of the waterbody.The geochemical research is necessary for predicting the negative impact of the polluted sediments on both the cage fish and the aquatic ecosystem.The sampling was conducted during various seasons of the year(February,June,August,October)which were characterized by the different fish feeding regimes.The sediment cores were collected at 7 points,including the cage and reference sites(150 m and 600 m far from the farm).The results showed that the accumulation of organic material released from the studied fish farms was local and the wastes did not enter the sediments at the control sites.Furthermore,the accumulated organic layer can be compacted and partially mineralized during winter period.Nevertheless,strongly reducing conditions in sediments occur due to the accumulation of organic material and low rate of water exchange within the studied bay.Therefore,there is a potential risk of formation of toxic gases and release of accumulated nutrients and metals from sediments to water.It can have a negative impact on benthic and nekton organisms,in particular cage fish.

Spatio-Temporal Patterns of Nitrogen and Phosphorus Stoichiometry in Cascade Ponds in an Agricultural Small Watershed and Their Influencing Factors

Ecological stoichiometry of nitrogen and phosphorus is an important indicator to characterize the nitrogen and phosphorus trophic status in aquatic ecosystems. The study of the spatio-temporal patterns of nitrogen and phosphorus stoichiometry is beneficial to the nitrogen and phosphorus pollution management in pond ecosystems. In this study, 18 groups (36 in total) of typical cascade ponds were selected as long-term observations to investigate the spatial distribution patterns of nitrogen and phosphorus component ratios (ratio of total nitrogen to phosphorus: TN:TP, ratio of dissolved nitrogen to phosphorus: TDN:TDP, ratio of particulate nitrogen to phosphorus: PN:PP) in water bodies in the tropical agricultural watershed of Jinjing. The results showed that the average values of TN:TP and TDN:TDP in the upstream ponds were 26.4 and 53.4, respectively, and were more than those in the downstream (22.95 and 48.1, respectively). In contrast, the PN:PP (13.78) in the upstream was significantly lower than that of the downstream (30.39). Furthermore, the factors of rainfall, agricultural land use and fish farming influenced the spatio-temporal variability of the N:P ratios. The ratios of TN:TP and TDN:TDP were higher in the wet season and lower in the dry season. Agricultural land use and fish farming reduced the ratios of the above three nitrogen and phosphorus components in cascade ponds in the study area. Our results show that strengthening agricultural land pollution control and aquaculture management could help to improve water quality of pond ecosystems in the study area.

A new analysis of fractional fish farm model associated with Mittag-Leffler-type kernel

In this paper,we analyze the dynamical behavior of fish farm model related to Atangana-Baleanu derivative of arbitrary order.The rnodel is constituted with the group of non-linear differential equations having nutrients,fish and mussel.We have included discrete kind gestational delay of fish.The solution of fish farm model is determined by employing homotopy analysis transforms method(HATM).Existence of and uniqueness of solution are studied through Picard-Lindelof approach.The influence of order of new non-integer order derivative on nutrients,fish and mussel is discussed.The complete study reveals that the outer food supplies manage the behavior of the model.Moreover,to show the outcomes of the study,some numerical results are demonstrated through graphs.