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STANDARDISATION OF HYDROACOUSTIC TECHNIQUES FOR FISH IN FRESH WATERS
Jon Hateley, Peter Clabburn, Vladislav Drastik, Malgorzata Godlewska, Jean Guillard, Jan Kubecka, Emma Morrissey, Stephen Thackeray, Ian Winfield
To cite this version:
Jon Hateley, Peter Clabburn, Vladislav Drastik, Malgorzata Godlewska, Jean Guillard, et al.. STAN- DARDISATION OF HYDROACOUSTIC TECHNIQUES FOR FISH IN FRESH WATERS. John S.
Papadakis; Leif Bjørnø. 1st Underwater Acoustics Conference and Exhibition Proceedings, pp.1595-
1600, 2013, 978-618-80725-0-3. �hal-03043781�
STANDARDISATION OF HYDROACOUSTIC TECHNIQUES FOR FISH IN FRESH WATERS
Jon Hateley
a, Peter Clabburn
b, Vladislav Drastik
c, Maágorzata Godlewska
d, Jean Guillard
e, Jan Kubecka
c, Emma Morrissey
f, Stephen J. Thackeray
gand Ian J. Winfield
ga
Environment Agency, U.K.
b
Natural Resources Wales, U.K.
c
Biology Centre of the Academy of Sciences of the Czech Republic, Czech Republic
d
Inland Fisheries Institute, Poland
e
INRA - UMR CARRTEL France
f
Inland Fisheries Ireland, R.O.I.
g
Centre for Ecology & Hydrology, U.K.
Maágorzata Godlewska, Inland Fisheries Institute, Oczapowskiego 10, 10-719 Olsztyn, Poland, margogod@wp.pl
Abstract: The European Union Water Framework Directive requires monitoring of biological quality elements to assess the ecological status of aquatic ecosystems and assure their good quality. Hydroacoustics could provide an effective tool for monitoring certain aspects of fish populations in fresh waters, but to ensure the comparability of datasets between lakes and reservoirs across Europe standardisation is required for equipment, survey design, data acquisition, data analysis, and data reporting. In the present paper we investigate the repeatability and precision of hydroacoustic fish surveys in a deep lake comprising two basins (mesotrophic and eutrophic) conducted in accordance with a provisional CEN standard. Results are presented from an international hydroacoustic intercalibration that included six systems comprising hardware from three manufacturers using four sound frequencies (70, 120, 200 and 400 kHz), together with analysis software from three manufacturers. The findings are very encouraging and demonstrate a considerable degree of similarity in the measures of fish biomass and fish abundance produced by these six diverse hydroacoustic systems operated under the mesotrophic and eutrophic conditions of this deep lake.
Keywords: hydroacoustics, fish biomass, Water Framework Directive, intercalibration
1. INTRODUCTION
The use of hydroacoustic systems for the assessment and monitoring of lake fish populations offers a non-destructive means of conducting rapid surveys. These methods have become increasingly popular over the last two decades, primarily as a result of advances in both hardware and software [1, 2, 3], but also in recognition of their potential for monitoring aquatic systems for the European Union Water Framework Directive [4, 5, 6, 7, 8]. Moreover, hydroacoustics provides information on lake fish distribution, abundance and size structure which complements more established, but invasive and labour-intensive, methods of biological sampling such as gill netting [9]. In Europe, particular efforts have been made in recent years to develop a standardised approach for this technique and a provisional standard has been developed under the auspices of the Comité Européen de Normalisation CEN [10]. These advances now require inter- laboratory comparisons of different hydroacoustic systems deployed by independent operators, which have been undertaken in the present work.
The specific objective of the present work was to demonstrate the repeatability and precision of hydroacoustic fish surveys in a deep lake when such are conducted in accordance with the provisional hydroacoustics standard described by [10].
2. METHODS
All field and analysis activities were conducted independently by a team of international hydroacoustic experts, each with an associated hydroacoustic system (tab. 1), that together comprised hardware from three manufacturers (BioSonics, HTI and Simrad) using four sound frequencies (70, 120, 200 and 400 kHz), together with analysis software from three manufacturers (Myriax, Lindem Data Acquisition and BioSonics).
System name
Model Sound frequency
(kHz)
Beam angle (°)
Pulse rate (pulses s
-1)
Pulse length (ms)
Vessel
EM Simrad EK 60 120 7.0 5 0.256 A
IJW BioSonics DTX 200 6.5 5 0.400 A
JG Simrad EK 60 70 11.0 5 0.256 A
JH HTI 241 200 6.0 5 0.200 B
JK Simrad EK 60 400 6.6 5 0.128 B
MG Simrad EK 60 200 7.0 5 0.256 A
Table 1. Key data collection attributes of six hydroacoustic systems used in the study.
Measurements were performed in the north (mesotrophic) and south (eutrophic) basins of the deep lake of Windermere, U.K., from 21 to 25 November 2012 during the day and night. Two vessels were deployed in a ‘leader’ and ‘follower’ configuration on the same pre-planned zig-zag transects (Fig. 1), incorporating a total of 20 transects, each approximately 500 m in length. More than one system was run simultaneously on each vessel.
Within the scope of the provisional standard, the fish biomass (as volume backscattering strength, S
v) and fish abundance (as areal densities of small (target strength
1st International Conference and Exhibition on Underwater Acoustics
-52 to -45 dB), medium (-45 to -37 dB), large (>-37 dB) and total fish) were estimated for each hydroacoustic system. Results were subsequently pooled to allow statistical comparisons to be made between the systems. In addition, in order to assess the degree of change in fish abundance over the course of the 3 days of fieldwork, day and night surveys were repeated for one system on the first and last survey dates.
Fig. 1. Locations of 20 hydroacoustic transects comprising the survey routes used in the north and south basins of the Windermere (NT = north transects, ST = south transects,
FH Ferry House peninsula.
3. RESULTS
At the level of individual transects within the entire dataset, the fish volume
backscattering coefficient sv ranged from -120.0 to -60.0 dB, small fish abundance from 0
to 970.4 fish ha
-1, medium fish abundance from 0 to 248.6 fish ha
-1, large fish abundance from 0 to 53.2 fish ha
-1, and total fish abundance from 0 to 1085.9 fish ha
-1.
Repeated observations on the first and last survey dates by the reference system, corresponding respectively to calm and very windy conditions, revealed that during the day fish biomass was significantly higher in both basins on the later date, as was small fish abundance in the south basin only. During the night, the only significant difference was observed in large fish abundance being lower in the south basin on the later date, although the statistical robustness of this finding was weakened by a high prevalence of zero values in the large fish data set. Thus, depending on the weather conditions natural variability of estimated fish abundance appeared to be quite high.
Between-systems comparisons indicated some differences for both day and night surveys. For the north basin, boxplots of the measures of fish biomass and fish abundance (Fig. 2) indicated that system JG tended to produce significantly higher values than those produced by other systems (all p <0.05). For the south basin, boxplots of the measures of fish biomass and fish abundance (Fig. 3) suggested some differences between systems, with the most obvious being systems IJW and JG tending to produce some relatively higher values. There was also a significant effect of system on total fish abundance, with the values produced by systems EM, MG and JH being significantly lower than those produced by systems IJW, JG and JK (all p <0.05).
Fig. 2 Boxplots of volume backscattering strength Sv and the total fish abundance during day and night in the north mesotrophic basin of Windermere
EM IJW JG JH JK MG
-120-100-80-70-60
NBAS day, Sv
EM IJW JG JH JK MG
050100150
NBAS day, Total
EM IJW JG JH JK MG
-90-85-80-75-70-65
NBAS night, Sv
EM IJW JG JH JK MG
050150250350
NBAS night, Total
1st International Conference and Exhibition on Underwater Acoustics
Fig. 3 Boxplots of volume backscattering strength Sv and the total fish abundance during day and night in the south eutrophic basin of Windermere
In summary, considerable and encouraging degrees of similarity in the measures of fish biomass and fish abundance were produced by the six independent hydroacoustic systems. However, there was a significant effect of system on almost all of the sets of comparisons, with the three exceptions being large fish in the north basin day surveys, large fish in the north basin night surveys, and large fish in the south basin night surveys.
In the future it is planned to investigate in detail the separate impacts on acoustic estimates of fish abundance of different acquisition and analysis parameters, such as sound frequency, pulse duration, SED criteria, thresholds etc. to identify which, if any, of these parameters need further standardisation.
4. ACKNOWLEDGEMENTS
We are grateful to Helge Balk, who provided invaluable software developments, and to numerous staff of the Freshwater Biological Association for the flexibility shown in their provision of some of the facilities and services used in this project.
REFERENCES
[1] Simmonds, J. & MacLennan, D., Fisheries Acoustics: Theory and Practice, 2
ndedition, Blackwell Science, Oxford, 437 pp., 2005.
EM IJW JG JH JK MG
-100-90-80-70
SBAS day, Sv
EM IJW JG JH JK MG
0100200300400500
SBAS day, Total
EM IJW JG JH JK MG
-85-80-75-70-65
SBAS night, Sv
EM IJW JG JH JK MG
0200400600800
