The presence of vessels in the ocean has a significant impact on marine mammals, including highly cultural species such as northern resident killer whales (NRKWs). NRKW engage in beach rubbing, a unique social behaviour where individuals approach shallow pebble beaches to rub against the stones. During rubbing bouts, the whales are exposed and vulnerable to disturbance. To investigate the effects of vessel disturbance on this important cultural behaviour, the initiation of rubbing and rubbing bout length were examined in relation to vessel presence and proximity. In July and August, for years 2020 and 2021, data were collected from an elevated observatory platform on the north side of Johnstone Strait, which has a visual line of sight to three rubbing beaches. NRKW behaviour and vessel characteristics were recorded, and a theodolite was used to collect spatially precise locational data on NRKWs and vessels in the study area. Two of the rubbing beaches are within the Robson Bight Michael Bigg Ecological Reserve (RBMBER), a marine reserve in Johnstone Strait that excludes recreational vessel traffic and one rubbing beach is adjacent to this marine reserve. Beach preference in the absence of vessels was evaluated to develop a baseline and allow for a comparison of rubbing behaviour in the presence of vessels. Data were then compared from beaches inside the reserve (reduced vessel presence) to the behaviour on the rubbing beach located outside the reserve (increased vessel presence). This study provided an opportunity to evaluate the benefits of a reserve in protecting Killer Whales from vessel disturbance and can help inform future policies and guidelines in Marine Protected Areas. These important findings are part of an overall evaluation of measures to protect the endangered Southern Resident Killer Whale population in the Salish Sea
