Hydroacoustic monitoring of the distribution, density and the mass-removal of pelagic fish in a eutrophic lake

Jurvelius, Juha; Sammalkorpi, Ilkka

doi:10.1007/bf00019373

Cited by 18 publications

(11 citation statements)

References 26 publications

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“…The increased proportion of multiple targets in deeper strata also could be related to a higher probability of including multiple echos as single targets because the critical target density, above which EC gives biased results, decreases as the square of the distance from the transducer (MacLennan and Simmonds 1992). The observed sharp vertical changes in bubble abundance with distance from the bottom indicates that the assumption about similarity of bubble densities in the hypolimnion and epilimnion, which frequently has been used for calculation of fish abundance using hydroacoustic techniques (e.g., Jurvelius and Sammalkorpi 1995), cannot be implemented without testing.…”

Section: Resultsmentioning

confidence: 99%

Methane bubbles in Lake Kinneret: Quantification and temporal and spatial heterogeneity

Ostrovsky

2003

Limnology & Oceanography

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The amount of methane bubbles rising from the bottom of Lake Kinneret was quantified by using a dual-beam echo sounder. Both echo-counting (EC) and echo integration (EI) techniques were implemented. Bubbles can confound the identification of fish targets because their acoustic sizes strongly overlap. Analysis of vertical changes in densities in the anoxic hypolimnion (with no fish) indicated that multiple targets were most abundant near the bottom, which caused an essential bias of bubble density estimates by EC. EI was a reliable tool for assessment of bubble density near the bottom. In the upper part of the water column, both techniques provided similar estimates of density of targets (mainly bubbles) because they were measured between dense fish schools during the daytime. The mean acoustic size of rising bubbles decreased in the hypolimnion but increased in the epilimnion, suggesting change in the relative importance of factors controlling gas volume. In summer and fall 2001, the bubbles became predominant echo-reflecting objects in the epilimnion. Temporal and spatial changes in bubble densities were highly heterogeneous, suggesting strong variability in factors affecting the gas ebullition. This variability should be taken into consideration when attempting to quantify the methane ebullition and assessing fish abundance in aquatic systems.

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Section: Resultsmentioning

confidence: 99%

Methane bubbles in Lake Kinneret: Quantification and temporal and spatial heterogeneity

Ostrovsky

2003

Limnology & Oceanography

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“…In our gillnetting, seining, trawling and hydroacoustics sampling the effect of daylight hours and water temperature on fish movements was taken into consideration in the sampling design (e.g. Jurvelius & Heikkinen, 1988;Jurvelius & Sammalkorpi, 1995). The results showed that in large lakes the fish community data obtained and the conclusions drawn from it are strongly affected by the sampling method.…”

Section: Discussionmentioning

confidence: 97%

Quality and status of fish stocks in lakes: gillnetting, seining, trawling and hydroacoustics as sampling methods

Jurvelius¹,

Kolari²,

Leskelä³

2010

Hydrobiologia

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All sampling methods give selective or biased estimates of fish species abundance, distribution and size structure. This creates problems, e.g. in regard to the Water Framework Directive of the European Union, which demands evaluation of the quality and status of fish stocks in lakes. We compared fish sampling by means of Nordic multimesh gillnets, seining, trawling and hydroacoustics in two Finnish lakes in summer 2007 and 2008. Sampling methods were used 'as such', i.e. no special design was implemented for method comparison. In the shallow eutrophicated lake the species' composition of gillnet sampling and seining were very different. The biomass-% of percids dropped from gillnet (61%) to seining (9%) and that of cyprinids grew from 39 to 90%, respectively. In the deep pelagic area of the oligotrophic lake, vendace and smelt predominated in trawl catches. The number of fish caught by gillnetting in that area was too small to make any conclusions about the species composition. In the eutrophicated lake, the combined length distribution for all fish species differed significantly between gillnetting and seining. In the oligotrophic lake, the gillnet catches were too small for any comparison of fish size. The difference in the length distribution of fish between trawl and echosounding was significant in most analysed depth layers. In upper depth layers acoustics sampled larger fish than trawling, and in deeper layers smaller fish. Using a combined acoustic-trawl method, the pelagic fish biomass was estimated to be approx. 17 kg ha -1 in the deep and oligotrophic lake. We conclude that in large and deep-water areas, the use of active gear is enough in fish sampling to evaluate the quality and status of fish stocks. Gillnetting together with seining is an appropriate method to work out the quality and status of fish stocks in shallow and littoral areas of large lakes. Variation in the catch selectivity of fish sampling gear requires a discrete ecological classification for each type of gear.

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“…Jurvelius and Sammalkorpi, 1995;Horppila et al, 1996;Turunen et al, 1997;Peltonen et al, 1999). In very few occasions, e.g.…”

Section: Introductionmentioning

confidence: 98%

Density and biomass of smelt (Osmerus eperlanus) in five Finnish lakes

Jurvelius¹,

Auvinen²,

Kolari³

et al. 2005

Fisheries Research

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Hydroacoustic monitoring of the distribution, density and the mass-removal of pelagic fish in a eutrophic lake

Cited by 18 publications

References 26 publications

Methane bubbles in Lake Kinneret: Quantification and temporal and spatial heterogeneity

Methane bubbles in Lake Kinneret: Quantification and temporal and spatial heterogeneity

Quality and status of fish stocks in lakes: gillnetting, seining, trawling and hydroacoustics as sampling methods

Density and biomass of smelt (Osmerus eperlanus) in five Finnish lakes

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