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Resource Issues: Vessel Traffic

thumb nail of recommended IMO shipping lanes
Current IMO recommended tracks (the San Francisco Traffic Separation Scheme (TSS) was updated June 1st, 2013)

Overview of the issue

There are approximately 4000 transits of the Sanctuary each year by large shipping vessels (greater than 300 gross tons), including container ships, bulk freighters, hazardous materials carries, and tankers. Vessel traffic within the Sanctuary was a major issue of concern raised during the designation process due to potential impacts from a large spill should one of these vessels ground along the coastline. For example, an oil spill could severely impact the sea otter population. The Sanctuary also hosts an abundance of whales and the National Marine Fisheries Service has identified vessel strikes as one of the threats that could impede the recovery of endangered whales so it is vital to understand vessel traffic in the Sanctuary, for more information on ship strikes see whale strikes.

How is the Sanctuary involved?

In 1997, the United States Coast Guard (USCG) and the National Oceanic and Atmospheric Administration (NOAA) established a workgroup of key stakeholders in the issue of vessel traffic, including representatives from federal, state and local governments, environmental groups and industry to review existing practices and risks, and recommend a package of strategies which would maximize protection of Sanctuary resources while allowing for the continuation of safe, efficient and environmentally sound transportation. The group's recommendations included alteration of the Traffic Separation Scheme (TSS) off San Francisco to move vessels away from the sensitive San Mateo shoreline. Most importantly, container ships, bulk freighters, and vessels carrying hazardous materials were moved offshore to reduce the risk of groundings, and organized into north-south lanes to reduce the risk of collision. These recommendations were ultimately approved by the International Maritime Organization (IMO), and implementation began in 2000. For details of the historic track changes please see the Vessel Traffic Management Plan Executive Summary.

figure 1: Previous Patterns of Vessel Traffic
Cargo vessel densities through MBNMS for May 2010. The color bar indicates the total number of minutes vessels spent in one square arc-minute of area over the course of the month. Figure from Christopher Miller at Naval Postgraduate School (NPS) from “Monthly distributions of shipping vessels within MBNMS for Jan-Dec2010."

In 2012, the Sanctuary staff provided input to the IMO to reduce ship strikes of whales on approaches to the San Francisco Bay ports and improve navigational safety. The San Francisco TSS lanes will be extended in 2013 due to the input from NOAA. For more information see the 2012 press release.


In 2013, Sanctuary staff collaborated with Southwest Fisheries Science Center (SWFSC) and Naval Postgraduate School (NPS) staff to analyze the use of the recommended tracks by cargo vessels and tankers to help determine if any additional management implementations are necessary to protect the Sanctuary's resources. SWFSC staff developed 2009 density maps for tankers and cargo vessels based on Automatic Identification System (AIS) data from MarineCadastre. NPS staff developed a Matlab code to detail daily deviations of the recommended tracks by cargo vessels and tankers for AIS data from September 2009 to 2012. Sanctuary staff reviewed AIS data daily to note any deviations and are working with United States Coast Guard staff to follow up with vessels traveling more than three nautical miles inside the recommended track for vessels 300 gross tons and above. The report, "Monterey Bay National Marine Sanctuary (MBNMS) Vessel Traffic Analysis: 2009-2012" (3.5M PDF), details how these three AIS data analyses do indicate that a great majority of the vessels that transit through the MBNMS are complying with the IMO recommended tracks.

Reviewed: April 11, 2024
Web Site Owner: National Ocean Service

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