Target strength of Nile tilapia (Oreochromis niloticus) from 200 kHz calibrated fish finder and scientific echosounder: laboratory measurement and modeling

Abstract

Target strength (TS) values from laboratory measurement and TS values from the model were measured and calculated from Nile tilapia (Oreochromis niloticus). Nile tilapia is one of the fastest growing aquaculture species, the fourth most produced fish globally, easily available in various sizes and lengths, and more importantly, it has a one-chambered swimbladder, which is suitable for TS measurement and modeling. The most common technique of measuring fish TS is utilizing a scientific echosounder. However, this instrument has a low implementation for small-scale fisheries due to its relatively high cost compared to the conventional fish finder. Thus, the objective of this study is to offer a solution that considers the instrument’s cost and usefulness using calibrated fish finder and scientific echosounder. TS values were produced by the two instruments that later being examined with TS from the Kirchhoff-ray mode (KRM) model to validate the result. Two single-beam echosounder instruments (Furuno FCV-628 fish finder and Simrad EK15 scientific echosounder) operated at a frequency of 200 kHz were used to assess the TS values for 30 samples of living Nile tilapia whose total length (TL) was in a range of 6 to 26 cm. In conclusion, statistically, the results showed no significant differences in TS measurement between the two instruments compared to TS values from the model. The TS values from the KRM model agreed well based on the regression analysis with the TS values from both instruments in the laboratory measurement.