In situ target-strength measurement of Peruvian jack mackerel (Trachurusmurphyi) obtained in the October-December 2011 scientific survey

摘要

The target strength (TS) of a species is a variable used for the biomass estimation, this force is a measurement of the received echo or reflected energy of the species, given by the sound wave transmission generated by the echo sounder. The objective of this work is developing the TS of the Peruvian jack mackerel (Trachurusmurphyi), using the technique in situ, the data were taken from a scientific Split Beam Echo sounder EK60 Simrad, at emission frequencies of 38 and 120 kHz, installed in the scientific research vessel José Olaya Balandra of the Institute of the Sea of Peru. In-situ measurements were made in 4 zones, where positive catches of jack mackerel were recorded. In order to obtain more accuracy in the target strength calculations, the following steps were used, by depth range, off-axis angle, compensation of the TS with respect to its angular position, through the post-acoustic data processing, Echoview 5.2. The results obtained were that the average TS of jack mackerel was between -38.11 and -38.79 dB, for 38 and 120 kHz respectively for a range of sizes from 27 to 38 cm of total length. These results are similar to those published for the same genus (i.e. Trachurustrachuruscapensis, Trachurustrachurus and Trachurus japonicus) and will allow to increase the precision and accuracy of the acoustic estimates for their fishing regulation. Finally, we intend to validate these equations, using industrial purse seine vessels to make captures in order to compare the captured and the inferred by means of the equations).