Ecosystem development in Lake Volkerak-Zoom: concept and strategy

1995 ◽  
Vol 31 (8) ◽  
pp. 239-243 ◽  
Author(s):  
W. Ligtvoet ◽  
S. A. de Jong
Keyword(s):  
Water Level ◽  
Fish Stock ◽  
Ecosystem Development ◽  
Optimal Conditions ◽  
Stock Management ◽  
Key Factors ◽  
Integrated Water Management ◽  
Ecological Concepts ◽  
Freshwater System ◽  
Water Level Management

In the 6000 ha Lake Volkerak-Zoom, a new freshwater system in the estuarine southwest of The Netherlands, biomanipulation is used as a tool in ecosystem development. The basic ecological concepts for ecosystem development are described. Key factors in the integrated water management are fish stock management and water level management, geared towards creating optimal conditions for northern pike, the dominant predator in mesotrophic waters. The main aspects of the water level management and the fish stock management are outlined.

scholarly journals The impact of water level fluctuations on the year class strength of roach: Implications for fish stock management

Limnologica ◽  
2008 ◽  
Vol 38 (3-4) ◽  
pp. 258-268 ◽  
Author(s):  
Uwe Kahl ◽  
Stephan Hülsmann ◽  
Robert J. Radke ◽  
Jürgen Benndorf
Keyword(s):  
Water Level ◽  
Water Level Fluctuations ◽  
Fish Stock ◽  
Stock Management ◽  
Class Strength ◽  
The Impact

Optimal Fisheries Investment under Uncertainty

1983 ◽  
Vol 40 (12) ◽  
pp. 2080-2091 ◽  
Author(s):  
Anthony T. Charles
Keyword(s):  
Optimal Investment ◽  
Fish Stock ◽  
Investment Strategies ◽  
Economic Optimization ◽  
Stock Management ◽  
Investment Under Uncertainty ◽  
Capital Costs ◽  
Wide Range ◽  
Full Analysis ◽  
Fishing Fleets

A full analysis of optimal fisheries investment strategies must take into account high levels of uncertainty in future fishery returns, as well as irreversibility of investment in specialized, nonmalleable fishing fleets. A stochastic optimization model is analyzed using dynamic programming to determine optimal policy functions for both fleet investment and fish stock management within an uncertain environment. The resulting policies are qualitatively similar to those found in the corresponding deterministic case, but quantitative differences can be substantial. Simulation results show that optimal fleet capacity should be expected to fluctuate over a fairly wide range, induced by stochastic variations in the biomass. However, the performance of a linear-cost risk-neutral fishery is fairly insensitive to variations in investment and escapement policies around their optimum levels, so that economic optimization is "forgiving" within this context. A framework of balancing upside and downside investment risks is used here to explain the roles of several fishery parameters in relation to optimal investment under uncertainty. In particular, the intrinsic growth rate of the resource and the ratio of unit capital costs to unit operating costs are found to be key parameters in determining whether investment should be higher or lower under uncertainty.

Groundwater-surface water relations in regulated lowland catchments; hydrological and hydrochemical effects of a major change in surface water level management

2019 ◽  
Vol 660 ◽  
pp. 1317-1326 ◽  
Author(s):  
Joachim Rozemeijer ◽  
Janneke Klein ◽  
Dimmie Hendriks ◽  
Wiebe Borren ◽  
Maarten Ouboter ◽  
...  
Keyword(s):  
Surface Water ◽  
Water Level ◽  
Water Relations ◽  
Major Change ◽  
Water Level Management

BIOFILM AND MERCURY AVAILABILITY AS KEY FACTORS FOR MERCURY ACCUMULATION IN FISH (CURIMATA CYPRINOIDES) FROM A DISTURBED AMAZONIAN FRESHWATER SYSTEM

2007 ◽  
Vol 26 (1) ◽  
pp. 45 ◽  
Author(s):  
Yannick Dominique ◽  
Régine Maury-Brachet ◽  
Bogdan Muresan ◽  
Régis Vigouroux ◽  
Sandrine Richard ◽  
...  
Keyword(s):  
Mercury Accumulation ◽  
Key Factors ◽  
Freshwater System

scholarly journals Response Surface Optimization of Supercritical Carbon Dioxide Extraction of Tea Polyphenols from Green Tea Scraps

2019 ◽  
Vol 102 (2) ◽  
pp. 451-456 ◽  
Author(s):  
Weifang Wang ◽  
Sai Han ◽  
Xianjun Zha ◽  
Jiangrui Cheng ◽  
Junying Song ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Response Surface ◽  
Green Tea ◽  
Maximum Yield ◽  
Extraction Process ◽  
Operating Conditions ◽  
Tea Polyphenols ◽  
Optimal Conditions ◽  
Key Factors

Abstract Background: The green tea scraps are the waste materials during the process of green tea production, and it is significant to extractvaluable tea polyphenols (TP) for reuse. Objective: The objective of this study was to extract valuable TP from green tea scraps, and the extraction conditions were optimized to obtain maximum yield of TP. Methods: The TPwere extracted by supercritical carbon dioxide (SC-CO2) with 65% (v/v) aqueous ethanol solution as cosolvent. The content of TP was determinedwith the Folin-Ciocalteu method. The key factors ofthe extraction process, including temperature (313.15–323.15 K), pressure (20–30 Mpa), and amount of cosolvent (50–150 mL) were optimized by response surface methodology (RSM). Results: These key factors showed the extremely complex effects on the extraction yield of TP. A second-order polynomial mathematical modelwasdeveloped for the response with high R-squared value (R2 = 0.9946) and used to predict the optimal conditions (i.e., temperature of 322.15 K, pressure of 23.60MPa, and amount of cosolvent of 150 mL). The verification experiments showed that the maximum yield ofTP was 23.07 ± 0.82% under the optimal conditions, which was in good agreement with the predicted value. Conclusions: TP can be successfully extracted from green tea scraps by SC-CO2, and RSM could be used to optimize the extraction process. Highlights: SC-CO2 extraction of TP from green tea scraps was developed. The operating conditions, including pressure, temperature, and amount of cosolvent, were optimized. RSM could successfully predict the optimal operating conditions.

Effect of 2,4-D and Various Salts on Eurasian Watermilfoil

Weed Science ◽  
1974 ◽  
Vol 22 (6) ◽  
pp. 591-594 ◽  
Author(s):  
Ronald A. Stanley
Keyword(s):  
Acetic Acid ◽  
Water Level ◽  
Aquatic Weed ◽  
Eurasian Watermilfoil ◽  
Laboratory Conditions ◽  
Mutual Antagonism ◽  
Tennessee Valley ◽  
Water Level Management ◽  
Dichlorophenoxy Acetic Acid

The management of Eurasian watermilfoil, an inimical aquatic weed in the Tennessee Valley, involves the use of water level management and herbicidal treatment with 2,4-D [(2,4-dichlorophenoxy)acetic acid]. The possible use of other chemicals to make 2,4-D more effective was tested by measuring growth of Eurasian watermilfoil under laboratory conditions with combinations of sublethal levels of 2,4-D and partially inhibitory concentrations of AlCl3, NH4Cl, Na2AsO2, BaCl2, Na2B4O7, CuSO4, HgCl2, Pb(NO3)2, NaCl, and ZnSO4. At the levels tested, BaCl2, Pb(NO3)2, and ZnSO4were only additive in effect with 2,4-D. Other compounds produced synergism at some concentrations and mutual antagonism at other levels. The greatest synergism was obtained by using HgCl2, AlCl3, and NaCl at 0.2 μM, 10.0 μM, and 200.00 mM respectively.

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