Using aerial surveys to fill gaps in AIS vessel traffic data to inform threat assessments, vessel management and planning

Abstract

AIS (Automatic Identification System) is a widely used source of data to spatially and temporally characterize marine vessel traffic and to subsequently estimate the direct and indirect threats maritime activities pose to marine and coastal environments. However, AIS data do not capture all vessel traffic in an area because not all vessels (e.g., recreational vessels) are required to carry AIS transponders. The goal of this study is to quantify the proportion of vessel traffic not transmitting AIS data by employing dedicated aerial surveys that simultaneously capture AIS data and georeferenced imagery of non-AIS vessels on the Canadian Pacific coast. Results show that 70% of vessel traffic in the surveyed area do not transmit AIS. The majority of these non-AIS vessels are recreational, making up 53% of the total vessels sighted. Analysis of historical AIS data in the survey area shows a steady increase in the voluntary uptake of AIS in the last decade. Results of this study can be used to adjust vessel traffic estimates and associated threats that are exclusively based on AIS data. This information can also benefit managers and policy makers that rely on AIS data when developing vessel traffic management measures to mitigate threats and to inform regional marine spatial plans. Place-specific studies to quantify marine vessel traffic missed by AIS are encouraged in coastal areas with high density of small vessel traffic.