Detecting anchored fish aggregating devices (FADs) and estimating use patterns from vessel tracking data in small scale tuna fisheries in Indonesia.

Supervisors: Britta D Hardesty, Chris Wilcox (Commonwealth Scientific and Industrial Research Organization, Tasmania).
Fishing demand is increasing linearly with the growth of the global human population. To respond to this increased demand, fishers have been looking for new fishing methods and technologies aimed to maximise fish extraction from the world’s oceans. The behaviour of fish, especially pelagic fish which aggregate underneath floating objects, has encouraged fishers to create artificial floating objects. These artificial objects that attract fish are called Fish Aggregative Devices (FADs) and they have helped the significant growth of world capture fisheries production by increasing fishing efficiency. However, the massive deployment of FADs in recent years has given rise to concern about the potential for negative consequences associated with FAD (over)fishing.

Fisheries authorities and regional fisheries management organizations (RFMO) have tried to manage the use of FADs in both coastal and high seas. However, due to illegal deployment and technical difficulties, FAD management is difficult. Moreover, due to the competitive nature of the fishing industry, fishing companies and individual fishers tend to avoid disclosing their FADs number and locations. This makes estimating the numbers of FADS as well as monitoring and managing FADs complex and difficult.

Regulatory changes in some parts of the world means that fishing vessels are required to have tracking devices to monitor their movements. However, in some regions, tracking of small-scale fishing vessels is voluntary. In three provinces in Indonesia, small-scale fishing vessels have opted to adopt a voluntary tracking program over the last two years. Based on their tracking data, we tried to detect the location and the use pattern of FADs and to estimate the catch rate and the number of FADs in use from the vessel movement.

A total of 48 FADs were detected as being visited by 34 fishing vessels from August 2016- January 2018. We learned that sharing FADs among vessels is common practice and that some FADs were visited multiple times in a year. We also identified that some FADs are visited over the course of more than one year, indicating that the lifetime of an individual FAD may exceed one year. Furthermore, results from the general additive model (GAM) showed that the length of the trip was more correlated to the total catch than was the number of FADs visited by a vessel in a single trip.