First target strength measurement of Trachurus mediterraneus and Scomber colias in the Mediterranean Sea

Antonio Palermino; Andrea De Felice; Giovanni Canduci; Ilaria Biagiotti; Ilaria Costantini; Sara Malavolti; Iole Leonori;

Knowing the species-specific target strength (TS) allows converting volume backscattering strength to numerical abundance. Since the acoustic surveys conducted for biomass assessment in the Mediterranean Sea currently focus on the echoes of two or three target pelagic species, the TS of non-target species has seldom been investigated in this basin. This is the first study of the TS of two pelagic species – Mediterranean horse mackerel (Trachurus mediterraneus) and Atlantic chub mackerel (Scomber colias) – in the Mediterranean Sea. A pilot approach using tethered live fish but not involving hooks and anesthetic was tested in experiments using a split-beam scientific echosounder operating at 38, 120, and 200 kHz. The mean TS was estimated for 29 live fish. The relationship between TS and fish length was determined with a standard linear regression model; the conversion parameter was obtained with the slope forced to 20. was computed at all frequencies for both species. The key values at 38 kHz were -71.4 dB for T. mediterraneus and -71.6 dB for S. colias. Although these results differ from those obtained with in situ and ex situ experiments using Pacific chub mackerel and other species of the genus Trachurus, they have the potential to provide new reference values for T. mediterraneus and S. colias biomass assessment in the Mediterranean Sea. The proposed method removes some potential biases due to the unnatural behavior of anesthetized fish. Moreover, it provides an alternative to hooks, although the use of a piece of rope instead of the hook seems to increase the acoustic reflectivity of the tethering apparatus.

2021 - Journal article

Fisheries research 240 (2021). doi:10.1016/j.fishres.2021.105973

Keywords: Fisheries acoustics, Target strength, Ex situ experiments, Mediterranean horse mackerel, Atlantic chub mackerel

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The research activities of the Institute are carried out in the context of research, development and innovation projects, both national and international, based on regional funding programs (POR FEAMPA - Regional Operational Program of the European Maritime Affairs Fisheries Fund and Aquaculture and POR FESR - Regional Operational Program of the European Regional Development Fund) or ministerial (PRIN - Projects of relevant national interest, PNRA - National Research Program in Antarctica, PO FEAMPA - National Operational Program European Maritime Affairs Fisheries and Aquaculture Fund) , programs for European Territorial Cooperation (Interreg), direct funding programs of the European Commission (Horizon2020 and Horizon Europe, Life, JPI - Joint Programming Initiatives, ERA-NET Cofund) and thematic collaboration initiatives managed by international organizations such as, for example , the FAO - GFCM (General Fisheries Commission for the Mediterranean). The Institute also develops funded projects in the context of collaborations with private companies in the sectors of the blue economy as well as technology transfer and research results. Research projects, mainly of a collaborative nature, are developed through a wide network of partners that include major Italian and foreign research institutions and universities.

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