Using anti-theft tracking devices to infer fishing vessel activity at sea

Quantifying accurately human impacts on marine ecosystems is key to healthy oceans. While fish production from wild stocks has plateaued since the 1980 s, those estimates are primarily drawn from large-scale commercial fisheries, whose boats are routinely monitored using a suite of sophisticated equipment to ensure compliance. Smaller vessels, however, especially in developing countries, have not been so rigorously scrutinised due to their sheer number and the associated high surveillance cost. This study investigated the viability of using low-cost anti-theft devices to detect spatio-temporal patterns of fishing activity in the small- to medium-scale snapper fishery of Indonesia. SPOT Trace® GPS tracking units (SPOT, LLC) were deployed on a voluntary, participatory basis, on 130 deep water fishing boats ranging from 1.5 to 29 m in length. GPS data were subsequently analysed through a port identification and trip segmentation algorithm, before using spatial clustering to automatically identify positions likely associated with fishing events. Through this procedure, we identified a total of 2650 fishing trips, whose durations ranged from 4.3 h to 55.3 days. Fishing occurred primarily near vessels’ home ports, but also offshore in the Jawa Timur province, and in the Timor and Arafura Sea near the Australian Economic Exclusion Zone (EEZ). Adopting this technology as a low-cost alternative to traditional VMS could greatly empower monitoring agencies through surveillance of a previously poorly documented stratum of the commercial fishing sector, and result in better long-term management of fish stocks and marine resources.