Estimation of fish biomass around the Sangihe Islands waters based on the acoustic data and numerical model of spatial ecosystem and population dynamics

Abstract

The Sangihe Islands is located in the Republic of Indonesia Fisheries Management Area (WPPNRI) 716, which has an area of about 52.5 million hectares. The potential productions for small and large pelagic fish in WPP NRI 716 are 332,635 tons/year and 181,491 tons/year, respectively, with utilization rates of 0.48 and 0.63. The dominant fish species caught were skipjack, mackerel, yellowfin tuna, and anchovies. In order to estimate fish biomass around the Sangihe Islands waters, acoustic data has been collected in several locations using a 120 kHz BIOSONIC DT-X echo sounder mounted on fishing vessels with purse seine gear. In addition, an analysis of the data from the results of the Spatial Ecosystem and Population Dynamics Model (SEAPODYM) from INDESO Project was also carried out. This model has a resolution of 1/12° and applied in Indonesian waters for 3 types of tuna, namely yellowfin, bigeye, and skipjack. Acoustic data showed that the largest fish biomass along the survey tracks was found at depths between 126 and 150 m, with a total biomass of 21,418 tons. Meanwhile, from the model results, it was found that skipjack biomass was the largest. The average biomass around the Sangihe Islands waters was around 1,340 tons.