2023_programme: Acoustic discrimination of juvenile yellowfin tuna (Thunnus albacares) in an offshore cage
- Session: 09. New frontiers in fisheries acoustics: applications- analysis- decision and management tools
Organiser(s): Victor Espinosa
- Lecture: Acoustic discrimination of juvenile yellowfin tuna (Thunnus albacares) in an offshore cage
Paper ID: 2083
Author(s): Sobradillo Bea, Boyra Guillermo, Uranga Jon, Moreno Gala Martínez Udane
Presenter: Sobradillo Bea
Abstract: Tuna fisheries support one of the most valuable markets worldwide, with over 50% of the catches obtained from drifting fish aggregating devices (dFADs). To locate and quantify tunas at FADs, acoustic technologies are mostly used by fishermen and scientists, considerably reducing the nominal effort, particularly in tropical purse seine fisheries. However, up to date, discrimination between species using purely acoustic methods has not yet been refined, lacking information on the acoustic response of each species at multiple frequencies. Three tuna species can be found simultaneously at FADs: skipjack (Katsuwanus pelamis), bigeye (Thunnus obesus) and yellowfin (Thunnus albacares) tuna, of which, only the acoustic frequency responses of SKJ and BET have been published. In this study, we present the results obtained from ex situ measurements of YFT, recorded at 38, 70, 120 and 200 kHz. Records were divided into two sets of data based on the type of analysis conducted: live tuna were used to describe the acoustic signal or target strength (TS; dB re 1m2) relationship with fish length across frequencies, and a dead specimen to study the TS variations with depth and tilt angle, under controlled conditions. Basically, a flat response across frequency was described for YFT, which, compared to the increasing and decreasing responses published for SKJ and BET, respectively, offered big potential for developing a discrimination algorithm for these 3 species.
- Corresponding author: Dr Beatriz Sobradillo
Affiliation: AZTI
Country: Spain
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