Acoustic identification of krill (Nyctiphanes couchii & Nematoscelis megalops) in the Spanish Mediterranean Sea

Abstract

During the 2015 routine acoustic survey for stock assessment carried out in the Spanish Mediterranean continental shelf, krill swarms were localized in two different places using an EK60 scientific echosounder, operating at multiple frequencies. Biological identification was performed by mean of a plankton net (bongo 90) equipped with two different mesh sizes (500 to 2000 microns). Although krill frequency response was similar in both localizations, samples analysis revealed the presence of two different species: Nyctiphanes couchii (Bell, 1853) and Nematoscelis megalops (Sars, 1883).