Evaluation of potential bias in observing fish with a DIDSON acoustic camera

Tušer, Michal; Frouzová, Jaroslava; Balk, Helge; Muška, Milan; Mrkvička, Tomáš; Kubečka, Jan

doi:10.1016/j.fishres.2014.02.031

Cited by 32 publications

(37 citation statements)

References 6 publications

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“…Target length was negatively correlated with the vertical direction and tortuosity . The estimated fish length agrees well with the actual length when the fish is positioned perpendicular to the centre of the multi-beam array (Tušer et al, 2014). In the present study, targets almost perpendicular to the beam axis were selected.…”

Section: Discussionsupporting

confidence: 77%

Measuring fish length and assessing behaviour in a high-biodiversity reach of the Upper Yangtze River using an acoustic camera and echo sounder

et al. 2016

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Summary In the past decade improved acoustic hard‐ and software have enabled estimations of abundance and distribution patterns of aquatic organism, including non‐intrusive monitoring of fish migrations and behaviour. In this study, a high frequency acoustic camera (DIDSON‐LR, 1.2 MHz, 0.7 MHz) and a portable split‐beam scientific echo sounder (Simrad EY60, 200 kHz) collected acoustic data on 192 and 157 individuals within 24 hr (19–20 April 2011) in the Mituo reach of the Yangtze River, China. Mean fish length estimated from the acoustic camera data was 18.7 ± 5.6 cm, with an average swimming speed of 0.19 ± 0.13 m s−1. The mean fish target strength (TS) produced by the echo sounder was −43.8 ± 4.4 dB, which corresponded to 5.7–119.9 cm fish length when converted by three different TS‐length equations. Average swimming speed was 0.11 ± 0.06 m s−1 from the echo sounder. Compared with the actual fish catch by the three layers of drift gill net in the survey area, the target length indicated by DIDSON was more accurate than the EY60 results, which were highly affected by the choice of TS length equations. It was determined that the two devices used synchronously could estimate fish length effectively to investigate their behaviour and distribution.

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Section: Discussionsupporting

confidence: 77%

Measuring fish length and assessing behaviour in a high-biodiversity reach of the Upper Yangtze River using an acoustic camera and echo sounder

et al. 2016

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“…Tušer et al . () noticed that length estimates were decreasing at off‐centre position of the beam. They explained it by a combination of the signal intensity of individual beams and the manner of fish reflection.…”

Section: Discussionmentioning

confidence: 95%

“…Working with a wider side aspect angle range, using tethered fish, Tušer et al . () described a L D decreasing with an increase in body aspect (side aspect angle), even for larger fish.…”

Section: Discussionmentioning

confidence: 97%

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Manual fish length measurement accuracy for adult river fish using an acoustic camera (DIDSON)

Daroux

Martignac

Nevoux

et al. 2019

Journal of Fish Biology

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Total lengths (LT) of 50 free‐swimming fish in a tank, silver carp Hypophthalmichthys molitrix and rainbow trout Oncorhynchus mykiss, were measured using a DIDSON (Dual‐frequency IDentification SONar) camera. Using Sound Metrics software, multiple measurements of each fish (LT, side aspect angle and distance from the camera) at different times were analysed by two experienced operators while a subset of data was analysed by two inexperienced operators. The main result showed high variability in intra‐fish LT measurements. The number of measurements required to minimise errors and to obtain robust fish measurements (true LT ± 3 cm) was estimated by a bootstrap method. Three to five measurements per fish were recommended for fish surveys in rivers. In this experimental study, aiming to reproduce river conditions, no evidence of fish position (side aspect angle and distance from the camera) effect was detected, but an operator effect (partially explained by training) was observed. General linear mixed models also showed that lengths of the smallest fish (LT < 57 cm) were overestimated and lengths of the largest fish (LT > 57 cm) were underestimated in comparison with their true lengths. In conclusion, we highlight that this technology, like any monitoring methods, returns imperfect observations. We advise DIDSON users to ensure that measurements are carried out correctly in order to draw accurate conclusion from this new technology.

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“…However, the TS-distribution pattern can help to distinguish between species of clearly different lengths. In the near future, acoustic cameras e.g., Didson will hopefully help to solve the problems in acoustic species identification (e.g., Lilja et al, 2013;Tuser et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

Fish density and target strength distribution of single fish echoes in varying light conditions with single and split beam echosounding and trawling

Jurvelius¹,

Marjomäki

Peltonen

et al. 2016

Hydrobiologia

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To evaluate the consistency of mobile and vertical echosounding results from the 1980s to the 2000s, fish density (fish ha -1 ) and target strength (TS, dB) estimates of single (70 and 200 kHz) and split (38 and 120 kHz) beam echo sounders were compared under varying light conditions. Acoustic estimates were compared with trawling results. During daytime hauls, the catch per swept area (CSA) of vendace and smelt were high at 10-15 m depth and low at 15-30 m depth. Around sunset, vendace and to some degree also smelt were concentrated at some meters above the thermocline. Around midnight, the CSA showed that smelt occupied higher water layers than vendace. Under different light conditions, both single and split beam echo sounders were in good agreement regarding the general level of fish density. In dusk and darkness, density estimates from echosounding and trawling as well as the TS-distribution between the single and split beam sounders were more consistent than those in daylight. We conclude that in boreal lakes single and split beam echosoundings outline, in comparable light conditions, consistent time series from the 1980s up to the year 2010. Darkness gives the best condition for estimating fish density and acoustic fish size.

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Evaluation of potential bias in observing fish with a DIDSON acoustic camera

Cited by 32 publications

References 6 publications

Measuring fish length and assessing behaviour in a high-biodiversity reach of the Upper Yangtze River using an acoustic camera and echo sounder

Measuring fish length and assessing behaviour in a high-biodiversity reach of the Upper Yangtze River using an acoustic camera and echo sounder

Manual fish length measurement accuracy for adult river fish using an acoustic camera (DIDSON)

Fish density and target strength distribution of single fish echoes in varying light conditions with single and split beam echosounding and trawling

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