scholarly journals Indirect economic indicators in bio-economic fishery models: agricultural price indicators and fish stocks in Lake Victoria

2005 ◽  
Vol 62 (3) ◽  
pp. 483-492 ◽  
Author(s):  
Silvio Simonit ◽  
Charles Perrings
Keyword(s):  
Nutrient Loading ◽  
Agricultural Land ◽  
Lake Victoria ◽  
Leading Indicators ◽  
Fish Stocks ◽  
Chl A ◽  
Run Off ◽  
Fishery Model ◽  
Agricultural Price ◽  
Point Pollution

Abstract We consider the potential for using prices as leading indicators of changes in stocks and yields in the freshwater capture fishery in Lake Victoria. Fertilizer run-off from agricultural land is a major cause of nutrient loading, along with soil erosion, atmospheric deposition, and point pollution from industrial and domestic affluent. The interactions between fertilizer applications, water quality, fish stocks, and yields are modelled in order to predict the effect of changes in the price of fertilizers on the fishery. The fishery model includes a measure of Chl a concentration (a proxy for phytoplankton density). The consequences of changes in Chl a concentration for fish stocks are modelled using Ecopath. We show that fertilizer prices are effective leading indicators of changes in fish biomass and yield.

scholarly journals Nutrient Loading, Temperature and Heat Wave Effects on Nutrients, Oxygen and Metabolism in Shallow Lake Mesocosms Pre-Adapted for 11 Years

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 127
Author(s):  
Erik Jeppesen ◽  
Joachim Audet ◽  
Thomas A. Davidson ◽  
Érika M. Neif ◽  
Yu Cao ◽  
...  
Keyword(s):  
Heat Wave ◽  
Shallow Lake ◽  
Nutrient Loading ◽  
Global Changes ◽  
Significant Positive Effect ◽  
Mixed Effect ◽  
Chl A ◽  
Nutrient Loadings ◽  
Positive Effect ◽  
Oxygen Concentrations

Global changes (e.g., warming and population growth) affect nutrient loadings and temperatures, but global warming also results in more frequent extreme events, such as heat waves. Using data from the world’s longest-running shallow lake experimental mesocosm facility, we studied the effects of different levels of nutrient loadings combined with varying temperatures, which also included a simulated 1-month summer heat wave (HW), on nutrient and oxygen concentrations, gross ecosystem primary production (GPP), ecosystem respiration (ER), net ecosystem production (NEP) and bacterioplankton production (BACPR). The mesocosms had two nutrient levels (high (HN) and low (LN)) combined with three different temperatures according to the IPCC 2007 warming scenarios (unheated, A2 and A2 + 50%) that were applied for 11 years prior to the present experiment. The simulated HW consisted of 5 °C extra temperature increases only in the A2 and A2 + 50% treatments applied from 1 July to 1 August 2014. Linear mixed effect modeling revealed a strong effect of nutrient treatment on the concentration of chlorophyll a (Chl-a), on various forms of phosphorus and nitrogen as well as on oxygen concentration and oxygen percentage (24 h means). Applying the full dataset, we also found a significant positive effect of nutrient loading on GPP, ER, NEP and BACPR, and of temperature on ER and BACPR. The HW had a significant positive effect on GPP and ER. When dividing the data into LN and HN, temperature also had a significant positive effect on Chl-a in LN and on orthophosphate in HN. Linear mixed models revealed differential effects of nutrients, Chl-a and macrophyte abundance (PVI) on the metabolism variables, with PVI being particularly important in the LN mesocosms. All metabolism variables also responded strongly to a cooling-low irradiance event in the middle of the HW, resulting in a severe drop in oxygen concentrations, not least in the HN heated mesocosms. Our results demonstrate strong effects of nutrients as well as an overall rapid response in oxygen metabolism and BACPR to changes in temperature, including HWs, making them sensitive ecosystem indicators of climate warming.

scholarly journals The Theory of Agricultural Price Bubble & Price Crash in Global Economy

2019 ◽  
Vol 6 (5) ◽  
pp. 168
Author(s):  
M.B. Dastagiri ◽  
L. Bhavigna
Keyword(s):  
Economic Theory ◽  
Developing Countries ◽  
Agricultural Land ◽  
Wholesale Price ◽  
Price Transmission ◽  
Price Fluctuations ◽  
Agricultural Prices ◽  
Forecasting Models ◽  
Price Bubble ◽  
Agricultural Price

Agricultural prices play greater role in living Economics. Since many decades’ farmers faced declining agricultural prices and low prices in developing countries. Therefore, in these countries agricultural price policies are under closer appraisal.  Government and policy makers worry about inflation. Economic precision is required in determining prices. This understanding led to conception of the study. The specific objectives are to review various agricultural price theories, research evidences and construct the theory of agricultural price bubble and crash and their effect on macro economy and suggest measures to improve. The study reviews various agricultural price theories, concepts, policies, research gaps and do meta-analysis and formulated the theory of Agricultural prices bubble and price crash. Since 1950, many development economists and practitioners prophesy in developing countries is that low agricultural commodities prices discourage poverty alleviation. Many countries are unable to make successful pricing policies due to there is not enough operative methodological and theoretical support for decision-making. According to the economic theory of cooperativism, the entities come closer to the pecking order theory. Unexpected changes and changes in regulations can have significant impact on the profitability of farming activities. “Demand channel" is the crucial factor in elucidation of commodity price growth. Future prices moments in agriculture have fat-tailed distributions and display quick and unpredicted price jumps. World Trade Organization study highlights the importance of strengthening multilateral disciplines on both import and export trade interventions to food price fluctuations to reduce beggar-thy-neighbor unilateral trade policy. The theory of NAFTA regionalism did not lead to regionalization and not increasing share of intraregional international trade. In EU countries land rents in modern agriculture causing upward trend in agricultural land prices. Information friction, agricultural supports, agricultural price & trade policies, agricultural price transmission are responsible price fluctuations. In economic theory, asymmetric price transmission has been the subject of considerable attention in agricultural gaps. Selection of forecasting models are based on chaos theory. Chaos in agricultural wholesale price data provides a good theoretical basis for selecting forecasting models. This theory can be applied to agricultural prices forecasting. Novelties in agricultural products fluctuations research offer scientific basis in planning of agricultural production.

scholarly journals Modeling of Phosphorous Load and Transport Pathways in Dhidhessa Catchment, Oromiya, Ethiopia

2019 ◽  
Vol 8 (3) ◽  
pp. 22-33
Author(s):  
Adisu Befekadu Kebede ◽  
Fekadu Fufa Feyessa ◽  
Wakjira Takala Dibaba
Keyword(s):  
Nutrient Loading ◽  
Assessment Tool ◽  
Organic Phosphorus ◽  
Swat Model ◽  
Chemical Properties ◽  
Management Plan ◽  
Transport Pathways ◽  
Best Management ◽  
Run Off ◽  
Physical And Chemical

Pollution of surface water with harmful chemicals and eutrophication with excess nutrients are recent serious environmental concerns. This lends the need of knowing the nutrient loading and transport mechanism that will occur with different spatial and temporal extent. Thus, effective information regarding the nutrients load and transport mechanisms are important to hydrologists, water use planners, watershed managers and decision makers for water resource projects and planet ecosystem. Our study aimed for modeling of phosphorous loading and its transport pathways and to identify the most vulnerable sub basin responsible for a significant phosphorus load in Dhidhessa catchment using Soil and Water Assessment Tool (SWAT) model. The pathways of phosphorus were identified and found that the organic phosphorus was dominant exporting mechanism accounted for 58.89% of the total path in the study area. For all forms of phosphorus, surface run off was the most dominant means of transport agent. The average annual loading of total phosphorus was identified as 20 kg ha-1. The sub basins 17, 23, and 3 were identified as the highest loading area of total phosphorous in the study catchment. Best management plan which is simple, economical and adaptable over the study catchment for managing severe impact of surface run off on water resources should be adopted. It is better to undergo detail re-examination over the physical and chemical properties of P in fertilizers and manures to propose the minimizing, neutralizing, replacing strategies to reduce at the source.

scholarly journals Modeling Dynamics of Prey-Predator Fishery Model with Harvesting: A Bioeconomic Model

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Charles Raymond ◽  
Alfred Hugo ◽  
Monica Kung’aro
Keyword(s):  
Global Stability ◽  
Lake Victoria ◽  
Equilibrium Points ◽  
Nile Perch ◽  
Type Ii ◽  
Bioeconomic Model ◽  
Eigenvalue Approach ◽  
Fishery Model ◽  
Predator System ◽  
Control Management

A mathematical model is proposed and analysed to study the dynamics of two-prey one predator system of fishery model with Holling type II function response. The effect of harvesting was incorporated to both populations and thoroughly analysed. We study the ecological dynamics of the Nile perch, cichlid, and tilapia fishes as prey-predator system of lake Victoria fishery in Tanzania. In both cases, by nondimensionalization of the system, the equilibrium points are computed and conditions for local and global stability of the system are obtained. Condition for local stability was obtained by eigenvalue approach and Routh-Hurwitz Criterion. Moreover, the global stability of the coexistence equilibrium point is proved by defining appropriate Lyapunov function. Bioeconomic equilibrium is analysed and numerical simulations are also carried out to verify the analytical results. The numerical results indicate that the three species would coexist if cichlid and tilapia fishes will not be overharvested as these populations contribute to the growth rates of Nile perch population. The fishery control management should be exercised to avoid overharvesting of cichlid and tilapia fishes.

scholarly journals Farming the waters: Bringing aquatic plant and animal species to agriculture

2000 ◽  
Vol 80 (2) ◽  
pp. 235-243
Author(s):  
John Castell
Keyword(s):  
Roman Empire ◽  
Agricultural Land ◽  
Agricultural Practices ◽  
Fish Farming ◽  
Maximum Sustainable Yield ◽  
Julius Caesar ◽  
Fish Stocks ◽  
The Past ◽  
The World ◽  
Important Means

Aquaculture has a long history, with carp culture in Asia starting before 2000 BC and oyster culture in the Roman Empire before the time of Julius Caesar. However, it is clearly the past 40 yr that have seen the most dramatic expansion of aquaculture. The world's population now exceeds 6 billion people and is still growing at an alarming rate. The world's wild fish harvest has clearly peaked at or above the maximum sustainable yield of about 90 million t. Many fish stocks are suffering from over-fishing and there is little hope of any increase in the capture fisheries production. Though modern agricultural practices have been very efficient at increasing the per acre yields, the world is experiencing an alarmingly steady decrease in the amount of agricultural land devoted to food production. In the past 20–30 yr production of fish, molluscs, crustaceans and aquatic plants (aquaculture) has become an increasingly important means of producing food, and in some countries aquaculture production accounts for more than half of the total fishery harvest and is even as high as 90% in a few countries. I have reviewed the historical growth of aquaculture, compared the product value in various countries and reviewed aquaculture practices for a number of plant, molluscan, crustacean and fish species around the world. These culture technologies were compared and contrasted with agricultural practices. Finally, some predictions for the future of aquaculture development in Canada and the world have been made. Key words: Canadian aquaculture, history, salmon, fish farming, production statistics, fish culture technology

Assessment and Mechanisms of Water Eutrophication in Chaohu Lake, China

2010 ◽  
Vol 113-116 ◽  
pp. 1433-1438
Author(s):  
Qing Guang Liu ◽  
Zong Guang Diao ◽  
Jing Yu Sun
Keyword(s):  
Natural Condition ◽  
Domestic Wastewater ◽  
Water Area ◽  
Ecological Environment ◽  
Chaohu Lake ◽  
Chl A ◽  
Routine Sampling ◽  
And Control ◽  
Water Eutrophication ◽  
Point Pollution

Water eutrophication has become one of the most serious problems in Chaohu Lake problem in recent years, and understanding the mechanisms of water eutrophication in Western Chaohu Lake will help for prevention and remediation of water eutrophication. In this paper, we selected 6 routine sampling sites in the water area of Chaohu Lake. TP, TN, CODMn and Chl-a are chosen to describe the eutrophication of the Study area. The influencing factors and major mechanisms of water eutrophication were discussed. The reasons of eutrophication changes in Western Chaohu Lake are very complicated; consist of the suitable natural condition, the built of Yuxi Gate, the deteriorated watershed ecological environment and a great amount of pollutants discharged. The treatment and control of the industrial and domestic wastewater from Hefei City are essential to the treatment. More attention should be paid to the treatment of non-point pollution.

scholarly journals Globally Consistent Assessment of Coastal Eutrophication

2021 ◽  
Author(s):  
Elígio Maúre ◽  
Genki Terauchi ◽  
Joji Ishizaka ◽  
Nicholas Clinton ◽  
Michael DeWitt
Keyword(s):  
Nutrient Loading ◽  
Temporal Trends ◽  
Well Being ◽  
Google Earth ◽  
Coastal Eutrophication ◽  
Chl A ◽  
Development Goals ◽  
Negative Impacts ◽  
Consistent Assessment ◽  
Increasing Trends

Abstract Eutrophication associated with increasing anthropogenic nutrient loading is an emerging global concern. Often, eutrophication is concomitant with negative impacts on ecosystems and human well-being. Nevertheless, the impacts and the extent of eutrophication are limited to regions with dedicated monitoring programmes. Here we introduce the Global Eutrophication Watch, the first global and interactive assessment map of coastal eutrophication potential (CEP). It is constructed on Google Earth Engine and it evaluates temporal trends in satellite chlorophyll-a (CHL), a proxy for phytoplankton biomass, to devise a global map of CEP. Our analyses suggest that, globally, coastal waters (depth ≤200 m) covering ~1.15 million km2 are eutrophic potential. We found that waters associated with CHL increasing trends—those with potential for further deterioration of water quality—are twofold higher than those showing signs of recovery. The tool effectively identified areas of known eutrophication with severe symptoms, such as dead zones, as well as those with limited to no information of the eutrophication. Our tool introduces the prospect for a consistent global assessment of eutrophication trends with major implications for monitoring Sustainable Development Goals (SDGs). This work contributes to the application of Earth Observations in support of SDGs.

scholarly journals Hydrologic analysis for river Nyando using SWAT

2011 ◽  
Vol 8 (1) ◽  
pp. 1765-1797 ◽  
Author(s):  
A. O. Opere ◽  
B. N. Okello
Keyword(s):  
Stream Flow ◽  
Input Data ◽  
Lake Victoria ◽  
Base Flow ◽  
Weather Data ◽  
Series Data ◽  
Organic Chemical ◽  
Primary Role ◽  
Time Step ◽  
Run Off

Abstract. The Nyando River is one of the major Rivers in the Lake Victoria Basin. It drains parts of Nandi, Kericho and Nyando districts. It has a catchment area of about 3600 km−2 of Western Kenya and an average discharge of approximately 15 m3 s−1, and has within it some of the most severe problems of environmental degradation and deepening poverty found anywhere in Kenya. The Nyando River drains into the Winam Gulf of Lake Victoria and is a major contributor of sediment. The primary role of GIS in hydrological modeling is to integrate the ever increasing volumes of diverse spatial and non spatial data. This can be the model input or output. Recent advance in GIS (hardware and software) technology offer unprecedented capabilities for storing and manipulating large quantities of detailed, spatially-distributed watershed data (ASCE, 1999). SWAT, which is an interface of Arc View GIS, uses Arc View to prepare input data and display the model output as spatial maps, charts or time series data. This makes it easy to study and display the information for assimilation by SWAT. SWAT is a continuous time model that operates on a daily/sub-daily time step. It is physically based and can operate on large basins for long periods of time (Arnold et al., 1998). The basic model inputs are rainfall, maximum and minimum temperature, radiation, wind speed, relative humidity, land cover, soil and elevation (DEM). The watershed is subdivided into sub-basins that are spatially related to one another. Routing in stream channel is divided in to Water, Sediment, nutrients and organic chemical routing (Neitsch et al., 2002a). Stream flow data was available for two Stations 1GD03 and 1GD07. The stations had data ranging from 1950 to 1997, though they had missing gaps. Rainfall data were available for twelve rainfall recording stations in and around the basin. The collected data ranges between 1960 and 2000 though there were quite a number of missing data. The other weather data used were temperature data (maximum and minimum) for Kericho and Kisumu Meteorological stations. During the study the available water capacity (SOL_AWC) was varied within the range of ±0.05 mm of water/mm of soil. The result showed that SOL_AWC affects the stream flow. SOL_AWC affects both the surface flow and base flow. An increase in SOL_AWC results in decrease on the stream flow because of increase in the ability of the soil to hold more water. An increase in the initial curve number (CN2) increases the stream flow, but the effect is more pronounced on the effects on surface run off. The slightly increase in total stream flow could be as a result of ration of surface run off to base flow. The amount of stream flow contributed by the base flow was more than 50% of the total stream flow as show by base flow separation. The goodness of fit between observed and simulated stream flow was assessed for the aforementioned (1GD03) station, the R2 was found to be 0.24 while the NSE was 0.46 respectively. The low value of R2 and NSE could be attributed to lots of data gaps in the station and also the effects of combined tributaries. The station is located about 10 km upstream of Ahero Bridge just before the flood plain. The model over estimated the low flows at this station while the high flows were well estimated. The performance of the model varied depending on the available input data. The coefficient of determination R2 varies for observed and simulated stream flow at River gauging Station. The relationship between land use/cover change and stream flow is very significant in Nyando basin. The observation made is that with decreased Forest Cover up to 0% there is increased stream flow mean and peak and increased forests cover i.e. 100% results in decreased mean and peak stream flow.

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