Spatial and temporal variability in shipping traffic around San Francisco Bay

Shipping traffic poses a worldwide threat to many large whale species. Risk assessments are\ud being used to mitigate the problem of ships striking whales. Most of these analyses use static\ud representations of shipping traffic. This study looks at shipping around San Francisco Bay\ud (SFB) at three temporal resolutions: 1) before and after implementation of the California Air\ud Resources Board???s Ocean-Going Vessels Fuel Rule (CARB rule), 2) between seasons, and 3)\ud day vs. night. I assessed spatial and temporal variability in cargo shipping traffic in the\ud Traffic Separation Scheme (TSS) using Automatic Identification System (AIS) data. I used\ud the nonparametric Mood???s Median test to compare median daily distances (MDD) because\ud the data were not normally distributed and did not have homogeneity of variance. While\ud differences between seasons were overall not significant, I found that day traffic was\ud generally higher than night traffic. Also, my Pre- and Post-CARB analyses showed\ud significantly less traffic in the alongshore Northern Outbound and Southern Inbound lanes\ud and more traffic in the offshore Western Inbound and Outbound lanes after the CARB rule\ud was imposed. I believe the CARB rule was largely responsible for these major shifts and\ud provides an example of how a regulation can strongly impact shipping traffic