Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints
Modern echosounders produce very accurate and versatile information on observed fish, but applicability of hydroacoustics in fish stock assessment is still largely determined by the behaviour of aquatic animals. A valid assessment is possible only when the target species avoid the inaccessible zones...
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ftunivhelsihelda:oai:helda.helsinki.fi:10138/239247 2023-08-20T04:06:26+02:00 Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints Kaikuluotauksen soveltuvuus Etelä-Suomen kuorejärvien ja Pohjois-Suomen siikajärvien kalakantojen arviointiin Malinen, Tommi University of Helsinki, Faculty of Biological and Environmental Sciences, Ecosystems and Environment Research Programme Helsingin yliopisto, bio- ja ympäristötieteellinen tiedekunta Helsingfors universitet, bio- och miljövetenskapliga fakulteten 2018-08-24T06:01:40Z application/pdf http://hdl.handle.net/10138/239247 eng eng 978-951-51-4465-2 http://hdl.handle.net/10138/239247 URN:ISBN:978-951-51-4465-2 Text Doctoral dissertation (article-based) Artikkeliväitöskirja Artikelavhandling doctoralThesis 2018 ftunivhelsihelda 2023-07-28T06:35:37Z Modern echosounders produce very accurate and versatile information on observed fish, but applicability of hydroacoustics in fish stock assessment is still largely determined by the behaviour of aquatic animals. A valid assessment is possible only when the target species avoid the inaccessible zones of echo sounder: surface blind zone, bottom dead zone and shallow areas. In addition, it requires an applicable method for eliminating echoes from other targets, especially phantom midge (Chaoborus) larvae, which are abundant in clay-turbid lakes. In Fennoscandia, acoustics has been widely used in vendace (Coregonus albula (L.)) stock monitoring due to its high economic value but other species have been less frequently assessed. In the present study, the applicability of hydroacoustics in fish stock assessment was investigated in two contrasting environments, in eutrophic, clay-turbid lakes dominated by smelt (Osmerus eperlanus (L.)) located in southern Finland and in oligotrophic, clear-water lakes dominated by whitefish (Coregonus lavaretus (L.)) located in northern Lapland. In both lake groups, the suitable diel periods and seasons for acoustic assessment were sought. In southern lakes, a new method was developed for eliminating the disturbance of Chaoborus. In northern lakes, the differences of the applicability of acoustics between whitefish populations were explored. The developed method enabled valid smelt density estimation also in lakes with abundant Chaoborus population. Without the new method, the smelt density would have been seriously overestimated. In southern lakes, the pelagic occurrence of smelt favours acoustic assessment. Both day and night surveys can be used and the suitable seasonal sampling window lasts from late July to October. However, because young-of-the-year smelt may occasionally inhabit shallow areas, acoustics should be supplemented by trawling in these areas. In highly turbid lakes, the surface blind zone may be a considerable source of bias and acoustics should be supplemented by ... Doctoral or Postdoctoral Thesis Fennoscandia Lapland Helsingfors Universitet: HELDA – Helsingin yliopiston digitaalinen arkisto |
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Open Polar |
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Helsingfors Universitet: HELDA – Helsingin yliopiston digitaalinen arkisto |
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ftunivhelsihelda |
language |
English |
description |
Modern echosounders produce very accurate and versatile information on observed fish, but applicability of hydroacoustics in fish stock assessment is still largely determined by the behaviour of aquatic animals. A valid assessment is possible only when the target species avoid the inaccessible zones of echo sounder: surface blind zone, bottom dead zone and shallow areas. In addition, it requires an applicable method for eliminating echoes from other targets, especially phantom midge (Chaoborus) larvae, which are abundant in clay-turbid lakes. In Fennoscandia, acoustics has been widely used in vendace (Coregonus albula (L.)) stock monitoring due to its high economic value but other species have been less frequently assessed. In the present study, the applicability of hydroacoustics in fish stock assessment was investigated in two contrasting environments, in eutrophic, clay-turbid lakes dominated by smelt (Osmerus eperlanus (L.)) located in southern Finland and in oligotrophic, clear-water lakes dominated by whitefish (Coregonus lavaretus (L.)) located in northern Lapland. In both lake groups, the suitable diel periods and seasons for acoustic assessment were sought. In southern lakes, a new method was developed for eliminating the disturbance of Chaoborus. In northern lakes, the differences of the applicability of acoustics between whitefish populations were explored. The developed method enabled valid smelt density estimation also in lakes with abundant Chaoborus population. Without the new method, the smelt density would have been seriously overestimated. In southern lakes, the pelagic occurrence of smelt favours acoustic assessment. Both day and night surveys can be used and the suitable seasonal sampling window lasts from late July to October. However, because young-of-the-year smelt may occasionally inhabit shallow areas, acoustics should be supplemented by trawling in these areas. In highly turbid lakes, the surface blind zone may be a considerable source of bias and acoustics should be supplemented by ... |
author2 |
University of Helsinki, Faculty of Biological and Environmental Sciences, Ecosystems and Environment Research Programme Helsingin yliopisto, bio- ja ympäristötieteellinen tiedekunta Helsingfors universitet, bio- och miljövetenskapliga fakulteten |
format |
Doctoral or Postdoctoral Thesis |
author |
Malinen, Tommi |
spellingShingle |
Malinen, Tommi Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints |
author_facet |
Malinen, Tommi |
author_sort |
Malinen, Tommi |
title |
Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints |
title_short |
Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints |
title_full |
Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints |
title_fullStr |
Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints |
title_full_unstemmed |
Hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints |
title_sort |
hydroacoustic fish stock assessment in southern and northern boreal lakes : potential and constraints |
publishDate |
2018 |
url |
http://hdl.handle.net/10138/239247 |
genre |
Fennoscandia Lapland |
genre_facet |
Fennoscandia Lapland |
op_relation |
978-951-51-4465-2 http://hdl.handle.net/10138/239247 URN:ISBN:978-951-51-4465-2 |
_version_ |
1774717480808218624 |