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Acoustic Data Harmonization: Target Strength Equations for Aegean Anchovy and Sardine

Explore the harmonization of acoustic data in the Mediterranean region from 2002 to 2006. Case study focuses on Aegean Sea utilizing the split beam method and regression analysis for target strength equations. Acoustic parameters, filtering techniques, and data exclusion criteria are discussed in detail from the 3rd AcousMed meeting in Heraklion, Crete, December 2011. Additional methods, in situ estimations, sensitivity analysis, and future suggestions like organizing a seminar on Echoview are also highlighted.

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Acoustic Data Harmonization: Target Strength Equations for Aegean Anchovy and Sardine

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  1. AcousMedHarmonization of the acoustic data in the Mediterranean 2002-2006 WP3.1 Target strength equations for anchovy & sardine Case Study: Aegean Sea HCMR-IMBR 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

  2. Protocol used… Split beam method 2 2nd meeting suggestions • Night Hauls monospecific >80% • Echoview used for analysis • Echo acquisition threshold: -60dB • Single targets concerning the whole water column • Acoustic parameters for single targets as in WGACEGG 08 • Bin range TS: 0.1 dB • Bin range TL: 0.5 cm • Regressions were conducted for each data set • Filtering on • - Single targets major axis angle -1o- 1o • - Fish tracks min number of single targets in a track ~ 2 • tortuosity 3D <3 1) best-fit Comparison of regression lines (α=0.05) 2) with a slope forced to 20 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

  3. Additional Filtering … Virtual echogram module in Echoview not licensed, thus Mask Filtering could not be applied, so we… • used the echoview plots: a) TS – target depth, b) TS distribution in order to filter plankton or targets that cannot be considered as anchovy/sardine • excluded strong single targets from the bottom layer (at least 5 meters above the bottom) • excluded single targets 5 m (or more) from the surface when plankton aggregations appear • checked the echogram for existing non dispersed shoals and excluded these regions from the analysis • excluded discontinuities in the echogram due to problems with the transducer. 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

  4. Data used… • Period: 2004-2010 • Sampling time: 20.30 – 04.45 • Majority of hauls deriving from summer surveys • 19 hauls >90% anchovy • 4 hauls >90% sardine • Max. bottom depth: 100 m • Majority of hauls max. bottom depth: 80m Map of the study area with the distribution of the hauls used 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

  5. Data not used… Which hauls were excluded? • Hauls with many non dispersed shoals through the echogram • Hauls with a lot of plankton that affects the results significantly • Hauls with noisy echograms, due to glitch in the transducer 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

  6. In situ TS estimations… Sardine Anchovy Slopes p-value: 0.953, ns difference Slopes p-value: 0.499, ns difference 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

  7. Sensitivity analysis… 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

  8. For the future… Suggestion!!! Organize a seminar about echoview and invite an expert from the support team of the software??? 3rd AcousMed meeting, Heraklion Crete 13-16 December 2011

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