Implications of low temporal resolution of vessel tracking systems

Abstract

Spatial and temporal fishing effort (FE) estimates are crucial for informing scientific-based decisions in fisheries management, spatial planning, and conservation. Lower temporal resolution (longer intervals between vessel position registrations) reduces FE accuracy, thus calling for a balance between precision and feasibility for large-scale mapping, such as in European waters. Effective marine management is critically dependent on this kind of accurate, comprehensive, and appropriate data. New EU legislation mandates tracking all fishing vessels, including small-scale fisheries (SSF) (LOA <= 12 m), implying a reassessment of optimal polling intervals. While experts recommend high-frequency polling (1 poll/30 s) for SSF, large-scale fisheries (LSF) have been mapped with up to 2-h polling intervals. Here, our study evaluates how polling frequency affects fishing activity characterization and FE estimation across fleets. We found that low temporal resolution critically affects (1) FE by underestimation, (2) misclassification of fishing behaviour, (3) compliance challenges, (4) marine spatial planning conflicts, (5) seafloor impact assessment (6) inaccurate bycatch risk analysis, (7) geographic projection biases, and (8) CPUE-based abundance indices, affecting stock and mortality estimates. These results highlight a central problem: low-resolution tracking compromises the scientific and management of outputs. The promise of high-resolution tracking to improve accuracy, is affected by the trade-offs between cost and data processing capacity, and the burden on vessel operators. Thus, SSF and passive gears should be tracked with at least a 30-s polling frequency as a conservative approach. For LSF using active gears, further work is required to determine the optimal ping frequency, but overall, it should be on the scale of a few minutes, depending on the gear used. To address this, our work clearly supports a recommendation for future regulations to define minimum acceptable polling intervals, tailored by fleet segment, and that support mechanisms be implemented to ease adoption. These regulatory aspects should contemplate a close collaboration with the fishing industry to ensure practicality, compliance, and long-term success. Thus, our findings highlight the costs of low-resolution tracking, providing critical insights for decision-makers shaping future vessel monitoring policies.