THE BIOMASS ESTIMATION OF SARDINELLA LEMURU IN BALI STRAIT USING HYDROACOUSTIC METHOD

• Main Author: Gede Merta Yoga Pratama, I
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76063
• Institution: Institut Teknologi Bandung

<p align="justify"> The Bali Strait area contains various fishery resources, one of which is Sardinella lemuru (locally known as Lemuru). Nevertheless, the community struggles to apply technology to estimate the biomass of Lemuru below sea levels. This research aims to estimate the biomass of Lemuru using hydroacoustic method, and to elaborate the relation of the estimated biomass with oceanographic parameters in Bali Strait. The primary data for this research was collected by BlueRobotics Ping Sonar Altimeter and Echosounder, oceanographic parameters collected by CTD and from satellite imagery. The processed data were quantitatively analyzed by its Target Strength (TS) and the estimation of fish length, weight, and density. The data validation was done by comparing the acoustic data calculation result to the 120 fish samples measured after being caught. This research resulted that, from the 3 catching trips of Lemuru in Bali Strait area, the Target Strength (TS) being in the range of -49,5 dB to -40,5 dB; the estimated fish length (L) of 7,94 cm to 22,4 cm; and the estimated fish weight of 5 grams to 112 grams. There were 13.712 fishes detected by the sensor with the average density of 1.733 ind/1.000m3. The estimated fish biomass is 1.042 kg in the water area of 7,3 km2 or 142 kg/km2, with trip 2 resulting the largest amount i.e. 496 kg from its 3 catching coordinates of Lemuru; whilst trip 3 resulting the smallest amount i.e. 252 kg. Compared to the water temperature during Lemuru fishing season (September-December) within the range of 24°C-28°C, the water temperature found by this research is slightly higher, being in the range of 27,9-29,9°C. Meanwhile, the Chlorophyl-a concentration based on Gauss' equation model resulted in this research is 0.2-0.83 mg/m3--lower than its concentration on fishing season, i.e. 0,5-0,9 mg/m3. The water salinity found by this research is 34,3 – 34,6 PSU; the value is higher than it is on fishing season, within the range of 29,19-33,97 PSU.