Application of a new shore-based vessel traffic monitoring system within San Francisco Bay

Vessel traffic management systems can be employed for environmental management

where vessel activity may be of concern. One such location is in San Francisco Bay

where a variety of vessel types transit a highly developed urban estuary. We analyzed

vessel presence and speed across space and time using vessel data from the Marine

Monitor, a vessel tracking system that integrates data from the Automatic Identification

System and a marine-radar sensor linked to a high-definition camera. In doing so, we

provide data that can inform collision risk to cetaceans who show an increased presence

in the Bay and evaluation of the value in incorporating data from multiple sources when

observing vessel traffic. We found that ferries traveled the greatest distance of any

vessel type. Ferries and other commercial vessels (e.g., cargo and tanker ships and

tug boats) traveled consistently in distinct paths while recreational traffic (e.g., motorized

recreational craft and sailing vessels) was more dispersed. Large shipping vessels often

traveled at speeds greater than 10 kn when transiting the study area, and ferries traveled

at speeds greater than 30 kn. We found that distance traveled and speed varied by

season for tugs, motorized recreational and sailing vessels. Distance traveled varied

across day and night for cargo ships, tugs, and ferries while speed varied between day

and night only for ferries. Between weekdays and weekends, distance traveled varied

for cargo ships, ferries, and sailing vessels, while speed varied for ferries, motorized

recreational craft, and sailing vessels. Radar-detected vessel traffic accounted for 33.9%

of the total track distance observed, highlighting the need to include data from multiple

vessel tracking systems to fully assess and manage vessel traffic in a densely populated

urban estuary.