In this work, we propose a non-invasive acoustic technique using ultrasound for the monitoring and control of larval development of gilthead seabream (Sparus aurata) in tanks. Biological measurements and target strength (TS) measurements have been carried out using a EK60 Simrad echosounder working at 200 kHz. The experiments have been carried out for three consecutive years in the marine aquaculture plant that Spanish Institute of Oceanography (IEO) has at Mazarron (Murcia, Spain). For the interpretation of the results, backscatter models were considered using the finite element method. The target strength values were evidenced with and without the presence of the developed swimbladder, showing a statistically significant relationship with the standard length, the area of the swimbladder and the percentage of larvae with a swimbladder
