Characteristics of skipjack tuna fisheries using FAD and non-FAD methods: an important step for fisheries management in The Gulf of Bone and Flores Sea, Indonesia

Skipjack tuna (Katsuwonus pelamis) is an important commodity from the global perspective. Skipjack tuna are caught using various fishing methods, either with or without the use of fish aggregating devices (FADs). In this study, we investigated skipjack tuna fishing characteristics using FAD and non-FAD methods. We used fisheries data from five years (2015-2019), including catch per unit effort (CPUE) and fish size, together with several oceanographic parameters around the fishing grounds in the Gulf of Bone and Flores Sea. We used statistical and spatial analyses to evaluate the differences in characteristics between the two fishing methods. The results showed that both the size at capture and the CPUE were significantly different between non-FAD and FAD fisheries. The size (fork length) of skipjack tuna caught using non-FAD methods ranged from 29 to 79 cm (average 55.3±9.4 cm) and was greater than for the FAD fisheries with a range of 18 to 58 cm (average 41.7±7.0 cm). Mean CPUE was also higher (85 fish/setting) for non-FAD compared to FAD fisheries (46 fish/setting). Skipjack tuna captured near non-FAD or free schooling areas showed a stronger association with relatively higher chlorophyll-a concentrations and deeper fishing areas than was the case in the FAD locations. This study suggests that to improve the potential catch, the proportion of fishing activities using non-FAD methods should be increased, implying that management of both FAD and non-FAD fisheries is vital for sustainable tuna fisheries and resource conservation.