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.
San Francisco Bay Area (left) with study area in the Central Bay (right) indicated by the solid black line. Locations of major ports, marinas, protected areas (California Department of Fish and Wildlife [CDFW], 2008), and ferry terminals (Golden Gate Bridge, Highway and Transportation District, 2017; San Francisco Bay Ferry, 2018) are also shown. San Francisco Bay Regulated Navigation Areas (RNAs) were digitized according to 33 CFR 165.1181. Those lying within study area boundaries are the North Ship Channel RNA and the Richmond Harbor RNA.
(a-f) Spatial distribution of trips per day and median speed for cargo (a), tanker (b), tug (c), ferry (d), motorized recreational (e), and sailing vessels (f). Cells colored blue indicate an average speed less than 10 kn, the voluntary speed restriction used in National Marine Sanctuaries outside SFB (United States Coast Guard [USCG], 2017). Locations of major ports, marinas, protected areas (California Department of Fish and Wildlife [CDFW], 2008), and ferry terminals (Golden Gate Bridge, Highway and Transportation District, 2017; San Francisco Bay Ferry, 2018) are also shown. San Francisco Bay Regulated Navigation Areas (RNAs) were digitized according to 33 CFR 165.1181.