Evaluating Risk of Ship Strike to Humpback Whales in San Francisco Bay

• Main Author: Rebekah Suzanne Lane
• Other Authors: Ellen Hines, Jerry Davis, Thomas J. Moore, Tim Markowitz
• Format: Master Thesis
• Language: English
• Published: San Francisco State University 2024
• Subjects: Humpback Whale; Megaptera novaeangliae
• Online Access: https://hdl.handle.net/20.500.12680/5x21tp913

Sightings of humpback whales (Megaptera novaeangliae) in the San Francisco Bay area were rare prior to 2016. Since then, humpback whales have been seen regularly entering the Bay between April and November, with an average of 167 sightings per year. The San Francisco-Pacifica Exclusion Area and adjacent waters are heavily transited by a variety of vessel types, including many recreational boats, high-speed ferries, and large ships. Considering the urbanized nature of the Bay, the potential for vessel strikes to humpback whales is high, as vessel traffic and whale habitat overlap in space and time. In this research, we used humpback whale sightings data from The Marine Mammal Center and vessel data obtained from Automatic Identification Systems for the years 2016 to 2019 to create a habitat risk assessment model for vessel interactions with humpback whales at the entrance to, and within, San Francisco Bay. We produced risk maps in a GIS analysis process for each season (spring, summer, fall) and vessel type (Cargo, Tanker, Tug/Tow, Passenger, Cruise, High-Speed Ferry, Pleasure) using the Habitat Risk Assessment toolbox from InVEST. This tool synthesizes spatiotemporal data for whales and vessels with expert ratings and literature reviews to assess risk. While vessel distribution, speed, and maximum risk remained consistent between seasonal delineations, patterns of vessel use varied between our seven vessel types. High-speed Ferry vessels had the highest maximum risk values of the vessel types listed, followed by Cargo vessels, though other vessel types covered larger portions of the study area with lower risk values. This is the first spatiotemporal risk assessment for vessel strike completed for humpback whales in the San Francisco Bay Exclusion Area and provides necessary information for targeted mitigation strategies for vessel strike of humpback whales in the San Francisco Bay area. https://doi.org/10.46569/5x21tp913