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1
Content available Hydroacoustic assessment of lake quality within the “dewelopment” project
Rustadbakken A, Godlewska M., Długoszewski B.
Hydroacoustics
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2010
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Vol. 13
215-224
EN
Deterioration of water quality and quantity is a world-wide problem. To prevent global water crisis, the European Water Framework Directive (WFD) requires that all European countries monitor aquatic ecosystems and ensure their good ecological status by 2015. Traditional methods of assessing water quality were mainly based on physico-chemical parameters of water, while WFD stresses importance of biological indicators and requires ecosystem approach within the whole water basin. With modern hydroacoustic equipment one can get not only detailed information on fish abundance, individual sizes, behavior, spatial and temporal distribution patterns, but also information on height, abundance and distribution of underwater vegetation and characteristics of bottom substrate. The acoustic measurements of fish and macrophytes were performed in 4 lakes of the river WEL catchment using Simrad split beam echosounder EK60, 70 kHz. Several acoustic metrics such as fish abundance, bubbles abundance and max vegetation depth were used as acoustic indicators of lake quality and compared with classification systems based on other quality indicators. The results have shown that hydroacoustics is a promising tool for monitoring and mapping an ecosystem.
2
Content available Can we distinguish acoustically between vendace stock and stickleback stock in lake Pluszne?
Doroszczyk L., Długoszewski B., Godlewska M.
Hydroacoustics
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2010
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Vol. 13
67-74
EN
Hydroacoustical monitoring of vendace stocks in lake Pluszne is performed regularly since 90-ties. However, in 2009 the lack of oxygen below the thermocline prevented fish to occupy the hypolimnion, which is its natural habitat. This led to a mixture of vendace and other fish species above the thermocline. The trawl catches accompanying hydroacoustical studies have contained exclusively vendace and stickleback. Investigation of TS have shown two-pick distributions, one corresponding to the size of vendace and one smaller. The two fish species were separated by thresholding. The maps of fish spatial distributions confirmed that vendace was present only in the deepest part of the lake, which is typical for this part of a year, while the other fish were distributed over the whole lake area. The worsening of environmental conditions in Lake Pluszne (increase of eutrophication) leads to declining vendace population.
3
Content available Day/night effects of passing boat on fish distribution in the shallow Malta reservoir
Godlewska M., Długoszewski B., Doroszczyk L.
Hydroacoustics
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2009
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Vol. 12
61-68
EN
Hydroacoustical measurements of fish population in the shallow Malta reservoir (mean depth <3 m) were performed in September and October 2008 using mobile horizontal beam. During the different time of day and night the same transects were covered in two directions, from the dam towards the upper part of the reservoir and back. During the day the number of fish registered on the returned way was lower than on the way forward in 83% of cases, and during the night in 67% of cases, however these differences were not statistically significant. Observation of fish at different distances from the boat have shown small avoidance reaction, especially for the small fish, that was similar during the day and at night, thus suggesting that mainly noise was responsible for the fish avoidance. Nevertheless, in shallow waters boat avoidance by fishes is of much less importance than in marine environment.
4
Content available Acoustical monitoring of fish at an electric barrier
Godlewska M., Doroszczyk L., Długoszewski B., Mokwa M.
Hydroacoustics
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2008
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Vol. 11
97-104
EN
Acoustical monitoring of fish at an electric barrier was performed using EY 500 split beam echo-sounder with the transducer directed horizontally. Stationary measurements done during the operating barrier and when the electric power was switched off have shown statistically significant difference in the number of fish approaching the barrier, 11 fish in the first case, and over 280 in the second. The electric barrier affected more strongly large fish than the small ones. Mobile measurements performed in a basin from which fish were approaching barrier revealed the higher fish concentration just in front of the operating barrier than elsewhere.
5
Content available Comparison of acoustical estimates of fish abundance for different coverage and survey design
Doroszczyk L., Długoszewski B., Godlewska M.
Hydroacoustics
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2007
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Vol. 10
33-38
EN
The aim of this paper is to investigate the influence of the degree of coverage, survey design, and method of calculation on fish abundance estimation results. Measurements were performed in deep, mesotrophic lake, containing fish community dominated by vendace (Coregonus albula L.). Two types of survey design were applied: the regular parallel transects with constant distance between them and the triangular (zig-zag) transects. It has been shown that at high enough degree of coverage both designs give equivalent estimates of fish abundance and similar fish distribution, however at lower coverage the parallel transects are preferable. With increasing degree of coverage the fish abundance increases as well until some asymptotic value, which is reached at degree of coverage equal to 0.8. The three different methods of estimating total stock have been applied: arithmetic mean, weighted mean, and kriging. The estimates of fish abundance received by the first two methods were very similar, while the third one was significantly lower.
6
Niestacjonarne stany cieplne i przepływowe w wybranych elementach agegatu chłodziarki domowej
Długoszewski B.
Prace Naukowe Politechniki Warszawskiej. Konferencje
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2000
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z. 20
123-130
PL
Omówiono procesy cieplne i przepływowe pod kątem teoretycznym modelowym wybranych elementów małego urządzenia chłodniczego i przedstawiono wybrane wyniki badań eksperymentalnych chłodziarki domowej.
EN
Theoretical model for thermal and flow transient states in some elements of a small-scale refrigeration system with a capillary tube has been proposed. Selected results of refrigerator experimental investigations have been presented.
7
Nieustalone procesy cieplne w małym urządzeniu chłodniczym
Długoszewski B.
Prace Naukowe Instytutu Techniki Cieplnej i Mechaniki Płynów Politechniki Wrocławskiej. Konferencje
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1998
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Vol. 53, nr 9
205-210
PL
Omówiono procesy cieplne i przepływowe pod kątem teoretycznym modelowym w małym urządzeniu chłodniczym i przedstawiono przykładowo wyniki badań eksperymentalnych chłodziarki domowej.
EN
Theoretical model of a small refrigerating system with capillary tube for transient states has been proposed.
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