Overestimation of percid fishes (Percidae) in gillnet sampling

Prchalová, Marie; Kubečka, Jan; Říha, Milan; Litvín, Radek; Čech, Martin; Frouzová, Jaroslava; Hladík, Milan; Hohausová, Eva; Peterka, Jiří; Vašek, Mojmír

doi:10.1016/j.fishres.2007.11.009

Cited by 31 publications

(26 citation statements)

References 54 publications

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“…Furthermore, cyprinids were significantly more predominant in the seining than in the gillnetting sample. This result is in accordance with Prchalova et al (2008) who found in eight central European reservoirs an overestimation of percid fishes in gillnet sampling. It was mainly due to the greater activity of perch compared to cyprinids during dusk and dawn.…”

Section: Discussionsupporting

confidence: 93%

“…This is a typical result in gillnet sampling compared to seining data (e.g. Prchalova et al 2008). However, based on the seining results the majority of the biomass consisted of cyprinids, and predatory fish did not exist.…”

Section: Discussionmentioning

confidence: 67%

“…Great attention must be paid on sampling of fish, since all sampling methods are more or less selective (e.g. Bethke et al, 1999;Prchalova et al, 2008;Olin et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 67%

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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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“…The gillnet is both a selective and a passive fishing gear, and therefore some species or sizes of fish can be over-or under-represented in a gillnet catch (see Kurkilahti, 1999;Prchalová et al, 2008Prchalová et al, , 2009a. Gillnet selectivity is also affected by saturation, which is caused by a limitation of space, its deformation when there are fish caught or fish avoidance of an occupied net.…”

Section: Introductionmentioning

confidence: 99%

A model of gillnet catch in relation to the catchable biomass, saturation, soak time and sampling period

et al. 2011

Self Cite

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“…If this is true it must be taken into account when applying indices of lake ecological status based on fish assemblages e.g., EQR4 [27]. Moreover, gillnet sampling overestimates the proportion of percids in relation to cyprinids [28] increasing the bias. The species-specific features can be complicated to model, as the accumulation effect might be a function of density and activity of the species itself or affected also by several other species with different effect sizes and, therefore, beyond the scope of this study.…”

Section: Discussionmentioning

confidence: 99%

Empirical Estimation of Accumulation-Induced Change in Gill Net Catchability: Mind the Observation Errors

Marjomäki¹,

Paloniemi²,

Keskinen³

et al. 2015

TOFISHSJ

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Abstract:We analyzed cumulative catches for 24 h gill net exposures divided into 4*6 h, 2*12 h and 1*24 h soak time treatments to estimate the reduction in its catchability due to accumulation of fish. The effects of loss of catch during net lifting, disturbance effect and fouling were eliminated as far as possible to reveal the true effect of accumulation. First we applied simple nonparametric and parametric tests in comparison of treatments. As expected, considerable reduction in catchability took place along with the increase in soak time, indicated by significantly lower total 24 h catches from longer soaks in comparison with shorter ones. The reduction was more pronounced for roach than for perch. Further, we compared a functional relationship regression (FRR), admitting correctly observation error variance also in the x-axis variable, with ordinary least squares regression (OLS) in modelling the relationship between cumulative 24 h catches for different treatments. We estimated the between-replicates proportional observation error variance within a treatment and found it to be similar in different treatments. Therefore the variance ratio could be assumed to be close to 1 enabling the use of major axis solution FRR. In this particular case the incorrect use of OLS obviously gives a seriously biased result, exacerbating the negative effect of accumulation for high x-axis values in comparison with FRR. We recommend the use of FRR for any analysis comparing different notoriously low precision fish abundance proxies.

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Overestimation of percid fishes (Percidae) in gillnet sampling

Cited by 31 publications

References 54 publications

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

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

A model of gillnet catch in relation to the catchable biomass, saturation, soak time and sampling period

Empirical Estimation of Accumulation-Induced Change in Gill Net Catchability: Mind the Observation Errors

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