Coldwater Fisheries Research Articles

Microsatellite marker 분석을 이용한 명태(Theragra chalcogramma) 5 집단의 유전적 다양성 및 유연관계 분석

한류성 어종인 명태는 우리나라 동해를 비롯한 일본, 러시아 북부의 오호츠크해, 베링해, 알래스카 등지에 서식하는 중요한 수산자원으로, 우리나라에서는 그 어획량이 매년 감소하고 있어, 그 자원량의 회복과 보존 및 관리가 필요한 대표적 어종이다. 그러나, 이러한 중요성에도 불구하고 국내에서 명태의 유전학적 집단 분석에 관한 연구는 많이 수행되지 않은 실정이다. 본 연구에서는 우리나라 동해, 러시아, 미국 명태 집단 및 일본 명태 집단과의 유전적 다양성과 유연관계를 분석하여 명태자원의 보존과 관리를 위한 과학적 자료를 제공하기 위해 유전적 다양성 및 계군 분석에 널리 사용되고 있는 microsatellite marker (msDNA) 8개를 사용하여 명태 집단의 유전자형을 분석하였다. 우리나라 동해, 러시아, 미국 및 일본 집단에서 채집된 총 186개체를 분석한 결과, 대립유전자수는 최소 7.13개에서 최대 10.63개로 나타났고, 평균 대립유전자의 수는 9.05개로 나타났다. 기대치와 관찰치 이형 접합율은 각각 0.698과 0.732로 조사되어, 현재 확보된 명태 집단의 유전적 다양성은 비교적 잘 유지되고 있는 것으로 나타났다. 유전학적 유연관계 분석을 위한 유전적 거리, Pairwise FST값, UPGMA와 주성분분석, AMOVA test 분석 결과, 우리나라 동해, 러시아, 미국의 명태 집단 간 유전적 차이는 거의 없었으나 일본 명태 집단과는 낮은 수치이지만 유의한 유전적 차이가 있음을 확인하였다(p<0.05). 본 연구에서 확인된 유전학적 분석을 통한 명태집단의 유전적 특성 및 주변국 집단과의 유연관계 분석결과는 우리나라 동해의 중요한 수산유전자원으로서의 명태에 대한 중요한 과학적인 근거자료가 될 것이며, 앞으로 명태 자원의 보존, 평가 및 이용에 활용 가능한 정보를 제공할 것이다. A comprehensive analysis of the genetic diversity and relationship of the cold-water fishery walleye pollock (Theragra chalcogramma), the most abundant economically important fishery resource in the East sea of Korea, has not been carried out, despite its importance in Korea. The present study assessed the genetic diversity and relationship between five walleye pollock populations (Korean population, Russian population, USA population, and Japanese populations) of T. chalcogramma using eight microsatellite DNA (msDNA) markers to provide the scientific data for the preservation and management of the Pollock fishery resource. The results of the analysis of 186 individuals of the Pollock revealed a range of 7.13-10.63 numbers of alleles (mean number of alleles=9.05). The means of observed heterozygosity (<TEX>$H_O$</TEX>), expected heterozygosity (<TEX>$H_E$</TEX>) were 0.732 and 0.698, respectively. The results of genetic distance, Pairwise <TEX>$F_{ST}$</TEX>, UPGMA (UPGMA: un-weighted pair-group method with an arithmetical average) (the phylogenetic tree), PCA (PCA: Principal Coordinate analysis) analysis pointed to significant differences between the Korean population, Russian population, USA population, and Japanese populations, although small (p<0.05). These results shed light on the genetic diversity and relationships of T. chalcogramma and can be utilized for research on the evaluation and conservation of Korean T. chalcogramma as genetic resources.

Morphometrics and length-weight relationship of Schizothoraxcurvifrons Heckel 1838 in River Jhelum, Kashmir, India

Schizothorax curvifrons, an indigenous cyprinid fish of Kashmir, forms an important coldwater fishery resource of the valley. This study was aimed to describe the morphometrics and length-weight relationship of S. curvifrons in River Jhelum Kashmir. The various morphometric characters showed high co-efficient of correlation (r) values, indicating that the characters were highly correlated to each other. The length-weight relationship was established logarithmically as Log W = -3.9323 + 2.5863 Log L (r2=0.746) for males, Log W = -4.1708 + 2.6852 (r2=0.745) Log L for females and Log W = -3.9975 + 2.6138 Log L (r2=0.746) for pooled data. The b value (2.6138) was found to be significantly different from 3 indicating negative allometric growth.

Scope of ornamental fisheries in snow fed rivers of Uttarakhand - Overview

Upland rivers of hills of Uttarakhand are unique in its ecosystem and biodiversity. These waters possess various varieties of ornamental fishes. The present study focuses on Scope of ornamental fisheries in snow fed rivers of Uttarakhand, along with challenges and opportunities. Besides the availability of resources peoples are not that much aware of ornamental fisheries of this region and these resources are yet not developed. The use of destructive fishing methods, habitat destruction leads to diversity destruction of hills stream fishes. As theseresources does not comprise fisheries of commercial importance due to sparse biota and low thermal scale, slow growth and very low natural food availability So, Directorate of Cold Water Fisheries is actively working in the field of survey and brood stock management of ornamental fish resources of cold water. Four hundred live cold water fishes including exotic gold and koi carp are being maintained at DCFR main complex for study and breeding trials. The recreational activities by fisheries department like ranching, sport fisheries development and development of ornamental fisheries of this region can lead to socioeconomic upliftment of hilly people and development of cold water ornamental fisheries in the state.

Relationships between Radiation and Canopy Closure Estimates in Streamside Buffers in Western Oregon

Maintenance of buffers for avoiding excessive increases in stream temperature for protecting cold water fisheries is prominent in riparian rules for forested streams in the Pacific Northwest. Four fish-bearing streams with basins of 250–400 ha in western Oregon were studied to determine how arrangement and amount of streamside buffers in clearcut units influenced riparian environments. Buffer designs included no-tree buffers, partial buffers 12 m wide, and two-sided buffers 15–30 m wide. Incident solar radiation estimates from fisheye photographs were compared to visual estimates of canopy closure, densiometer estimates of canopy closure, and basal area. Based on individual sample points, regression analyses of radiation estimates resulted in r2 values of 0.65 for visual estimates of canopy closure; 0.72 for spherical densiometer, directed south; 0.52 for basal area from in-stream sample points placed at 30-m intervals; and 0.63 for basal area from inventory points 15 m from the stream. High variability existed around all of the lines; r2 values increased 0.10–0.30 when unit means were used. Canopy closure estimators, such as densiometers, can offer less time-consuming and less expensive methods than direct measures of radiation to estimate the amount of radiation that might reach a stream through streamside buffers.

Simulating the effect of climate change on stream temperature in the Trout Lake Watershed, Wisconsin

The potential for increases in stream temperature across many spatial and temporal scales as a result of climate change can pose a difficult challenge for environmental managers, especially when addressing thermal requirements for sensitive aquatic species. This study evaluates simulated changes to the thermal regime of three northern Wisconsin streams in response to a projected changing climate using a modeling framework and considers implications of thermal stresses to the fish community. The Stream Network Temperature Model (SNTEMP) was used in combination with a coupled groundwater and surface water flow model to assess forecasts in climate from six global circulation models and three emission scenarios. Model results suggest that annual average stream temperature will steadily increase approximately 1.1 to 3.2°C (varying by stream) by the year 2100 with differences in magnitude between emission scenarios. Daily mean stream temperature during the months of July and August, a period when cold-water fish communities are most sensitive, showed excursions from optimal temperatures with increased frequency compared to current conditions. Projections of daily mean stream temperature, in some cases, were no longer in the range necessary to sustain a cold water fishery.

Sensitivity of lake thermal and mixing dynamics to climate change

Warming-induced changes in lake thermal and mixing regimes present risks to water quality and ecosystem services provided by U.S. lakes and reservoirs. Modulation of responses by different physical and hydroclimatic settings are not well understood. We explore the potential effects of climate change on 27 lake “archetypes” representative of a range of lakes and reservoirs occurring throughout the U.S. Archetypes are based on different combinations of depth, surface area, and water clarity. LISSS, a one-dimensional dynamic thermal simulation model, is applied to assess lake response to multiple mid-21st century change scenarios applied to nine baseline climate series from different hydroclimatic regions of the U.S. Results show surface water temperature increases of about 77 % of increase in average air temperature change. Bottom temperature changes are less (around 30 %) for deep lakes and in regions that maintain mid-winter air temperatures below freezing. Significant decreases in length of ice cover are projected, and the extent and strength of stratification will increase throughout the U.S., with systematic differences associated with depth, surface area, and clarity. These projected responses suggest a range of future challenges that lake managers are likely to face. Changes in thermal and mixing dynamics suggest increased risk of summer hypoxic conditions and cyanobacterial blooms. Increased water temperatures above the summer thermocline could be a problem for cold water fisheries management in many lakes. Climate-induced changes in water balance and mass inputs of nutrients may further exacerbate the vulnerability of lakes to climate change.

Natural and anthropogenic controls over suspended sediments within a mountainous Appalachian watershed: implications for watershed restoration

The upper Elk River (620 km2), located in mountainous east-central West Virginia, is one of the premier cold-water fisheries in the eastern United States. However, sediment run-off from both forestry and non-forestry-related disturbance has the potential to threaten the quality of wild trout populations. General linear models were used to link spatial and temporal variation in total suspended solid (TSS) concentrations throughout the watershed to natural (i.e. landform and geology) and anthropogenic (forest management practices, other land-use disturbance [residential and commercial development, agriculture, and recreation], census roads) landscape attributes. In addition, through a unique paired sampling design, we tested the hypothesis that increasing levels of disturbance (i.e. forest management and other land use activities) within a watershed would result in a proportional increase in TSS concentrations. Spatial variation in TSS concentration was found to primarily be explained by land-use disturbance (partial R2 = 0.66) and secondarily by forest management practices (R2 = 0.13) and road area (R2 = 0.08). Results of a paired sampling design further indicated that significant increases in TSS concentrations were the result of intense land-use disturbance associated with activities other than forest management. Temporal variability (i.e. CV) in TSS was primarily related to dry flat area (partial R2 = 0.28) and percent calcareous bedrock (R2 = 0.21), suggesting natural sedimentation processes associated with karst geologies may exacerbate effects of anthropogenic disturbance. These results suggest that forestry-related best management practices being used in this mountainous region were effective in reducing sediment loads to nearby waterbodies, and improved management of non-forestry disturbance may be needed to protect this valuable fishery from sediment-related impacts.

Developing and testing temperature models for regulated systems: A case study on the Upper Delaware River

Summary Water temperature is an important driver of many processes in riverine ecosystems. If reservoirs are present, their releases can greatly influence downstream water temperatures. Models are important tools in understanding the influence these releases may have on the thermal regimes of downstream rivers. In this study, we developed and tested a suite of models to predict river temperature at a location downstream of two reservoirs in the Upper Delaware River (USA), a section of river that is managed to support a world-class coldwater fishery. Three empirical models were tested, including a Generalized Least Squares Model with a cosine trend (GLScos), AutoRegressive Integrated Moving Average (ARIMA), and Artificial Neural Network (ANN). We also tested one mechanistic Heat Flux Model (HFM) that was based on energy gain and loss. Predictor variables used in model development included climate data (e.g., solar radiation, wind speed, etc.) collected from a nearby weather station and temperature and hydrologic data from upstream U.S. Geological Survey gages. Models were developed with a training dataset that consisted of data from 2008 to 2011; they were then independently validated with a test dataset from 2012. Model accuracy was evaluated using root mean square error (RMSE), Nash Sutcliffe efficiency (NSE), percent bias (PBIAS), and index of agreement ( d ) statistics. Model forecast success was evaluated using baseline-modified prime index of agreement (md) at the one, three, and five day predictions. All five models accurately predicted daily mean river temperature across the entire training dataset (RMSE = 0.58–1.311, NSE = 0.99–0.97, d = 0.98–0.99); ARIMA was most accurate (RMSE = 0.57, NSE = 0.99), but each model, other than ARIMA, showed short periods of under- or over-predicting observed warmer temperatures. For the training dataset, all models besides ARIMA had overestimation bias (PBIAS = −0.10 to −1.30). Validation analyses showed all models performed well; the HFM model was the most accurate compared other models (RMSE = 0.92, both NSE = 0.98, d = 0.99) and the ARIMA model was least accurate (RMSE = 2.06, NSE = 0.92, d = 0.98); however, all models had an overestimation bias (PBIAS = −4.1 to −10.20). Aside from the one day forecast ARIMA model (md = 0.53), all models forecasted fairly well at the one, three, and five day forecasts (md = 0.77–0.96). Overall, we were successful in developing models predicting daily mean temperature across a broad range of temperatures. These models, specifically the GLScos, ANN, and HFM, may serve as important tools for predicting conditions and managing thermal releases in regulated river systems such as the Delaware River. Further model development may be important in customizing predictions for particular biological or ecological needs, or for particular temporal or spatial scales.

Hypolimnetic oxygenation in Twin Lakes, WA. Part I: Distribution and movement of trout

Summer temperature/dissolved oxygen squeeze conditions have negatively impacted coldwater fisheries, including rainbow (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis), in North and South Twin lakes of northeastern Washington. In 2009, line diffuser hypolimnetic oxygenation (HO) was initiated in North Twin to prevent anoxia and increase summer trout habitat. Suitable trout habitat volume increased from a low of 0% preoxygenation to 100% of the North Twin hypolimnion following HO. To assess if trout utilized the expanded habitat following oxygenation, summer trout movements and habitat utilization were assessed from 2006 through 2012 using various combinations of ultrasonic telemetry, archival tags, gillnetting, and hydroacoustics. Trout utilized North Twin hypolimnetic habitat more frequently compared to pre-HO years and to unoxygenated South Twin, and swim speeds significantly decreased with oxygenation. Chaoborus zooplankton distributions have also changed following HO; water column densities were significantly lower with oxygenation compared to preoxygenation and to unoxygenated South Twin.

Hypolimnetic oxygenation in Twin Lakes, WA. Part II: Feeding ecology of a mixed cold- and warmwater fish community

Line-diffuser hypolimnetic oxygenation (HO) was initiated in North Twin Lake, Washington, in 2009 to mitigate loss of coldwater fishery habitat due to temperature–dissolved oxygen “habitat squeeze” and to reduce internal phosphorus cycling. Active tracking, net-captures, and hydroacoustic analyses demonstrated that trout populations rapidly expanded into increased hypolimnetic habitat within the first few years of oxygenation; however, long-term fishery benefits and many basic ecological aspects of HO have yet to be established. Diet and food web analyses indicate significant changes in feeding ecology of principal coldwater fish species in North Twin in 2012 compared to preoxygenation (2005) and to unoxygenated South Twin in 2012. North Twin rainbow trout (Oncorhynchus mykiss) consumed significantly more large-bodied Daphnia during midsummer 2012 than in South Twin, where rainbow trout fed primarily on littoral amphipods. Additionally, relative gut weight for brook trout (Salvelinus fontinalis) in August 2012 was significantly higher in North Twin compared to South Twin, apparently due to increased access to hypolimnetic zooplankton. Golden shiner (Notemigonus crysoleucas) diets also seem to include more zooplankton in oxygenated North Twin. Littoral-focused largemouth bass (Micropterus salmoides) diets were not altered by HO. Observed changes in feeding ecology following HO have significant implications for future fishery management in the Twin Lakes.

Climate change impacts on freshwater fish, coral reefs, and related ecosystem services in the United States

We analyzed the potential physical and economic impacts of climate change on freshwater fisheries and coral reefs in the United States, examining a reference case and two policy scenarios that limit global greenhouse gas (GHG) emissions. We modeled shifts in suitable habitat for three freshwater fish guilds and changes in coral reef cover for three regions. We estimated resulting economic impacts from projected changes in recreational fishing and changes in recreational use of coral reefs. In general, coldwater fisheries are projected to be replaced by less desirable fisheries over the 21st century, but these impacts are reduced under the GHG mitigation scenarios. Similarly, coral cover is projected to decline over the 21st century primarily due to multiple bleaching events, but the GHG mitigation scenarios delay these declines in Hawaii (but not in South Florida or Puerto Rico). Using a benefit-transfer approach, we estimated that global policies limiting GHG emissions would provide economic benefits in the range of $10–28 billion over the 21st century through maintaining higher values for recreational services for all freshwater fisheries and coral reefs, compared to the reference scenario. These economic values are a subset of the total economic and societal benefits associated with avoiding projected future declines in freshwater fisheries and coral reef cover due to unmitigated climate change.

Production Analysis of Inland Fish in Angul District of Odisha

The objective of this paper is to analyse the production of inland fish in Angul district of Odisha. The study is based on primary data collected from 250 fisher men from two blocks of the district. The Production of inland fisherman is positively related to its land, days of fishing, hours of fishing, cost of net used & water area of production. The days of fishing varying from 50 days to 300 days in a year. 38 numbers of fisherman households are working 100-150 days & 26 fishermen are working with the period ranging from 50-100 days. Only 7 numbers of inland fishermen are giving maximum days towards fish cultivation, those who are not doing any other work for their livelihood. Income of inland fisherman is positively related to its land, days of fishing, hours of fishing, cost of net used & water area of production. th position in fish production among the fishing nations of the world and the number one position with regard to export of prawns. India as a maritime country has a vast potential of fishing resources comprising 2 million Sq. Kms of exclusive economic zone for deep fishing 7,520 Kms coast line, 29,000 Kms of rivers, 1.7 million hectares of reservoirs, nearly 1 million hectares of brackish water area and 0.8 million hectares of tanks and ponds for inland and marine fish production. Indian fisheries and aquaculture are important sectors of food production, providing nutritional security to the food basket, contributing to the agricultural exports and engaging about fourteen million people in different activities. With diverse resources ranging from deep seas to lakes in the mountains and more than 10% of the global biodiversity in terms of fish and shellfish species, the country has shown continuous and sustained increments in fish production since independence. Constituting about 4.4% of the global fish production, the sector contributes to 1.07% of the GDP and 4.7% of the agricultural GDP. The total fish production of 6.4 million metric tonnes presently has nearly 55% contribution from the inland sector and nearly the same from culture fisheries. Paradigm shifts in terms of increasing contributions from inland sector and further from aquaculture are significant over the years. With high growth rates, the different facets of marine fisheries, coastal aquaculture, mariculture inland fisheries, freshwater aquaculture and coldwater fisheries are increasingly being diversified, contributing to food, health, economy, exports, employment and tourism of the country.

Capture Efficiency of Barbed versus Barbless Artificial Flies for Trout

AbstractI examined the capture efficiency of artificial flies fished with barbed and barbless hooks in various coldwater fisheries throughout California. Capture efficiency was defined as the proportion of trout (family Salmonidae) landed to the total number of trout hooked while angling. Waters were selected based on high catch per unit effort along with trout species present in an effort to increase the probability of encounters and the species represented. Artificial flies were standardized by J‐style hooks and three artificial fly types (dry, nymph, and streamer). In an effort to reduce bias, anglers were not told what hook type (i.e., barbed or barbless) they were using and were not allowed to handle or visually inspect flies. A total of 1,617 trout were landed with a mean total length of 213 mm and a range of 64–660 mm. Mean capture efficiency (and ranges) was 76% (38–100%) for anglers using barbed flies and 63% (0–100%) for anglers using barbless flies. Results show that anglers using barbless flies landed proportionately less trout than when they used barbed flies. Fisheries managers must weigh any perceived benefits from barbless regulations with potential reductions in catch rates and associated angler satisfaction.Received May 24, 2012; accepted January 17, 2013

Nutrient indicators of agricultural impacts in the tributaries of a large lake

Lake Simcoe in Ontario, Canada, is a large lake surrounded by a mix of urban, agricultural, and less developed areas and is showing adverse effects from excess nutrient inputs, including low hypolimnetic oxygen concentrations. Knowledge of both the quantity and quality of nutrients and seston entering the lake is important because large reductions in phosphorus (P) loads have been proposed to help restore the lake and its coldwater fishery. We examined land use effects on P quality (i.e., bioavailability) and its relationship to seston in the tributaries of Lake Simcoe. Indicators of agricultural impacts were examined in 13 tributaries of Lake Simcoe, which were selected to represent a range of land use types. Bioavailability of P was assessed through analysis of different forms of P and stoichiometric indicators of nutrient status in seston. Nutrient sources were examined using the δ15N of seston. The percentage of cropland in the subwatershed had a strong relationship with P as reflected in higher soluble reactive P concentrations and lower indicators of P deficiency. Cropland land use effects were complicated; they contributed highly bioavailable P to a P deficient lake, and at the same time, contributed high seston loads causing turbidity, resulting in light deficiency. In the Lake Simcoe watershed, animal manure application on cropland could be a source of nutrients related to the δ15N variability and, correspondingly, bioavailable P. Management efforts should therefore include best management practices to reduce manure application to croplands and to prevent runoff from areas where manure is stored.

Year-round patterns in bacterial production and biomass in Lake Simcoe, Ontario, Canada: are heterotrophic bacteria a significant contributor to low hypolimnetic oxygen?

Bacteria serve an important function in aquatic environments and are associated with nutrient regeneration, carbon (C) metabolism, and secondary production. This is the first study to measure heterotrophic bacterial production, abundance, biomass, and biovolume in Lake Simcoe, Ontario. Excessive phosphorus loading resulting in low hypolimnetic oxygen concentrations has impacted the cold-water fishery in Lake Simcoe. We tested the hypothesis that bacteria contributed to dissolved oxygen declines in Lake Simcoe and examined the environmental factors impacting bacterial activity. Spatial and temporal variations in the microbial community were measured from June 2010 to July 2011. A dual-isotope method (3H-TdR and 14C-leu) was used, resulting in mean (± standard deviation) annual epilimnetic bacterial production estimates of 0.130 ± 0.173 and 0.268 ± 0.304 μg C L−1 h−1, respectively. The mean annual bacterial abundance was 1.49 ± 1.53 cells × 109 L−1, with a mean biomass of 1.21 ± 1.34 μg C L−1 and a mean biovolume of 0.0043 ± 0.0030 μm3 cell−1. These estimates had distinct seasonal patterns, with consistently lower bacterial activity in the winter relative to the spring, summer, and fall. Differences between epilimnetic and hypolimnetic bacterial activity were inconsistent for the 4 bacterial parameters measured. Lake temperature, chlorophyll a, and dissolved organic C concentrations were the most significant factors influencing the annual epilimnetic patterns in the examined bacterial parameters. Annual bacterial production was low in Lake Simcoe and does not seem to be a major contributor to the low hypolimnetic oxygen concentrations in the lake.

Adaptive management and governance of Delaware River water resources

This paper articulates the complexities of adaptively managing Delaware River water resources to meet shifting priorities of drinking water supply, drought mitigation and flood mitigation, as well as conflicting stakeholder interests. In particular, the paper examines the short-term and long-term programs that comprise the Delaware River Basin Commission's (DRBC) and the 1954 US Supreme Court Decree parties' successful adaptive management approach that seeks to balance the growing list of demands for water resources management, including drinking water supply, drought management, flood control and cold water fisheries protection. Review of the DRBC's adaptive governance approach reveals the critical complexities of designing experimental, yet science-driven management approaches and effectively engaging various sets of stakeholders in the associated decision-making processes.

Climate change impacts on freshwater recreational fishing in the United States

We estimated the biological and economic impacts of climate change on freshwater fisheries in the United States (U.S.). Changes in stream temperatures, flows, and the spatial extent of suitable thermal habitats for fish guilds were modeled for the coterminous U.S. using a range of projected changes in temperature and precipitation caused by increased greenhouse gases (GHGs). Based on modeled shifts in available thermal habitat for fish guilds, we estimated potential economic impacts associated with changes in freshwater recreational fishing using a national-scale economic model of recreational fishing behavior. In general, the spatial distribution of coldwater fisheries is projected to contract, being replaced by warm/cool water and high-thermally tolerant, lower recreational priority (i.e., “rough”) fisheries. Changes in thermal habitat suitability become more pronounced under higher emissions scenarios and at later time periods. Under the highest GHG emissions scenario, by year 2100 habitat for coldwater fisheries is projected to decline by roughly 50 % and be largely confined to mountainous areas in the western U.S. and very limited areas of New England and the Appalachians. The economic model projects a decline in coldwater fishing days ranging from 1.25 million in 2030 to 6.42 million by 2100 and that the total present value of national economic losses to freshwater recreational fishing from 2009 to 2100 could range from $81 million to $6.4 billion, depending on the emissions scenario and the choice of discount rate.

Treatment of Water Supplies by the Technique of Dynamic Aeration

The problems of water quality are related to the decrease in the dissolved oxygen content, particularly in the lower layers. These lower layers may deteriorate significantly if the dissolved oxygen consummated in biochemical processes is not renewed by surface aeration or photosynthesis. Thermal stratification of lakes and reservoirs can result in substantial hypolimnetic oxygen depletion, which may have a negative impact on the cold-water fisheries, the drinking- water treatment process, and water quality downstream of hydropower reservoirs. The main purpose of this study is to show the effect of hypolimetic aeration and destratification mode to improve the concentration of oxygen dissolved and level of phosphorus in the depths of the lake. The 10.3 km2 of the water of Hallwil lake are an important tourist center for the canton of Lucerne (Switzerland).Before its restoration in the winter of the year 1985/1986, this lake eutrophication showed significant disruption of aquatic activities, and pollution damage to its various uses, and thus inhibited the development of tourism in the region. Thus, the long periods of stratifications, associated to an important amount of an organic material (principally phosphorus), were originally caused by frequent anoxic phases of the deep layers. This anoxia could be noted beyond 3 m of depth. For this, the Swiss Federal Institute for Aquatic Science and Technology (Eawag) in Switzerland, to address the eutrophication of Hallwil lake, put into service in the winter of 1985/1986, an installation of a aeration system in two alternate modes of aeration namely by a aeration system in winter by destratification mode and aeration hypolimnetic in summer (air / pure oxygen). Through the exhibition of the different results of the chemical parameters (dissolved oxygen, total phosphorus) in the two aeration modes, we were able to ensure an improvement of the lake water quality As a result, the average value of oxygen dissolved and the amount of phosphorus is found in the range of allowed values are: -Winter Season: [O2]min ≥ 8g/m3; [P2]max ≤ 0.15g/m3 - Summer Season: (30 m ≥H ≥15 m): [O2]min ≥ 5g/m3; [P2]max ≤ 0. 13g/m3 Consequently, we can conclude that both techniques aeration method has contributed radically in valuable way to improve the amount of dissolved oxygen and decrease the concentration of phosphorus in the deep layers of the lake.

Study of the Oxygen Transfer Efficiencies in the Different Methods Used in the Technique of Hypolimnetic Aeration

Thermal stratification of lakes and reservoirs can result in substantial hypolimnetic oxygen depletion, which may have a negative impact on the cold-water fisheries, the drinking water treatment process, and water quality downstream of hydropower reservoirs. Several techniques of aeration are presented in this study, to describe their effectiveness in control of physical and chemical parameters, that compromising the balance ecological and the thermal stratification in water supplies. As a result, we demonstrate that the most efficient hypolimnetic aeration system is the bubble plume diffuser; although an accidental destratification may occur. In hypolimnetic aeration systems, the aeration system by bubble plume appears to be the most economic and perhaps the simplest among the systems used in Stanley lake (Colorado, U.S.A), even as other researches select Speece Cone aeration system, or the full airlift systems, or the TVA line diffuser. The purpose of this study is to show the oxygen transfer efficiencies in the different methods used in the technique of hypolimnetic aeration, and their effect on the preservation of the thermal stratification. As well, this study concentrate on the economic and technical sides associated to these aeration systems.

Study of the Oxygen Transfer Efficiencies in the Different Methods Used in the Technique of Hypolimnetic Aeration

Thermal stratification of lakes and reservoirs can result in substantial hypolimnetic oxygen depletion, which may have a negative impact on the cold-water fisheries, the drinking water treatment process, and water quality downstream of hydropower reservoirs. Several techniques of aeration are presented in this study, to describe their effectiveness in control of physical and chemical parameters, that compromising the balance ecological and the thermal stratification in water supplies. As a result, we demonstrate that the most efficient hypolimnetic aeration system is the bubble plume diffuser; although an accidental destratification may occur. In hypolimnetic aeration systems, the aeration system by bubble plume appears to be the most economic and perhaps the simplest among the systems used in Stanley lake (Colorado, U.S.A), even as other researches select Speece Cone aeration system, or the full airlift systems, or the TVA line diffuser. The purpose of this study is to show the oxygen transfer efficiencies in the different methods used in the technique of hypolimnetic aeration, and their effect on the preservation of the thermal stratification. As well, this study concentrate on the economic and technical sides associated to these aeration systems.