The use of statistical models in identifying skipjack tuna habitat characteristics during the Southeast Monsoon in the Bone Gulf, Indonesia

Safruddin, Hidayat R, Farhum SA, Zainuddin M. 2022. The use of statistical models in identifying skipjack tuna habitat characteristics during the Southeast Monsoon in the Bone Gulf, Indonesia. Biodiversitas 23: 2231-2237. Skipjack tuna (Katsuwonus pelamis) is the main fishery product in the Bone Gulf, Indonesia, since it has high economic value and is widely accepted by the market. The migration of skipjack tuna can be described by oceanographic dynamics, influenced by seasonal changes. This study aimed to explore the relationship between the oceanographic factors and the distribution and abundance of skipjack tuna obtained by pole and line fishing in the Bone Gulf, Indonesia. The research was conducted during the southeast monsoon season (April-September) from 2015 until 2018. Three oceanographic parameters were used to understand this relationship, i.e., Sea Surface Temperature (SST), Sea Surface Chlorophyll-a (SSC), and water depth. Generalized Additive Models (GAMs) and Generalized Linear Models (GLMs) used to predict the spatial pattern of the skipjack tuna showed that all considered parameters significant influenced the distribution of skipjack tuna in the study area. The fish are mostly distributed from coastal to offshore areas, ranging between 50 to 2000 meters and even wider. The concentration tends to be high within the range of 29.5 to 30.5°C of SST, 0.25 to 0.35 mgm-3 of SSC, and 500 to 1500 meters of water depth. The research also found that the skipjack tuna migration to the Bone Gulf may have followed the current water interruption during the southeast monsoon, for preferred warmer temperatures and lower primary productivity waters in the offshore areas. This factor may represent the optimal habitat of skipjack tuna during the period and can be the basis for determining the skipjack fishing schedule in the Bone Gulf.