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Title: Variability in Mobile Acoustic Fish Community Assessment
Author: Hateley J
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1224, Representation ID: 395, Object ID: 2439; Environment Agency Project ID:EAPRJOUT_1245, Representation ID: 409, Object ID: 2456
Hydroacoustics is a cost-effective tool for surveying fish communities in large lowland rivers and lakes and will be a key element in providing temporal and spatial data for the national fisheries monitoring programme and the Water Framework Directive. In order to improve robustness of information obtained from horizontal hydroacoustic fisheries surveys, this project was commissioned to account for the observed sampling variability. Two potential sources of variability were examined: 1) Differences between echosounders in operation. 2) Variability due to key abiotic factors affecting fish behaviour. One dual-beam (BioSonics model 102) and two split-beam (HTI model 241, Simrad EY500) echosounders were tested for variability in reported target strength (TS) and fish density. The objectives of these comparisons were: - A recommended standard echosounder system for Environment Agency mobile horizontal surveys. - To validate cross-calibration of echosounder outputs, enabling comparisons between rivers surveyed using different gears. This study concluded that the variability in reported TS is of little significance in the context of mobile horizontal surveys. The HTI would be recommended as the standard Agency system for such surveys primarily based on single target reporting and user-definable ping-rates, however other systems must be gradually phased out with substantial (but undefined) overlap periods to enable cross-calibration of acoustic outputs. Finally, recommendations were made for the design of a future programme to determine the influences of abiotic factors on acoustic estimates. These included; use of a single echosounder system, studies on a number of sites and rivers with differing properties, multiple measurements of environmental parameters and combined mobile / fixed location studies.
Publisher: Environment Agency
Subject Keywords: Stock assessmentRiversAcousticsFreshwater fishesRiversLakesBiological surveysFishesEchosoundingMonitoringFreshwater ecology
Extent: 83
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