Jumbo squid (Dosidicus gigas) in situ target strength measurements in northwest Mexico

In order to convert acoustic abundance indexes into biomass is essential to establish the relationship between squid size dorsal mantle length (DML) and acoustic Target Strength (TS). We had carried out in situ measurement in 2012 off Baja California on Dosidicus gigas. For both frequencies, we found significant differences between modes of measured and predicted TS distributions, 6 and 11 dB for 120 and 38 kHz, respectively. It is known that TS varies with several factors, including echosounder characteristics and transducer frequency and mainly the target orientation in the acoustic beam and many other biological variables. In relation to squid behavior, during the capture operation small fish schools were observed in the area, which may suggest that squid were feeding. Further observations and analysis are necessary in order to obtain reliable TS - DML relationship for jumbo squid before attempting acoustic biomass assessment methods to this important species.