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AcousMed Harmonization of the acoustic data in the Mediterranean 2002-2006

AcousMed Harmonization of the acoustic data in the Mediterranean 2002-2006. WP3.1 Target strength equations for anchovy & sardine. Case Study: Aegean Sea. HCMR-IMBR. 3 rd AcousMed meeting, Heraklion Crete 13-16 December 2011. Protocol used…. Split beam method 2.

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AcousMed Harmonization of the acoustic data in the Mediterranean 2002-2006

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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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