Disrupting the herd: Recreational boating alters group dispersion within beluga whale herds

Abstract There is limited knowledge about the presence and potential impacts of recreational boats in marine mammal habitats. While numerous studies have examined marine mammal responses to commercial vessels, icebreakers, or whale‐watching boats, the specific influence of private recreational boats remains understudied. This knowledge gap is particularly notable for the endangered St. Lawrence population of beluga whales ( Delphinapterus leucas ). In this study, we conducted land‐based observations of recreational boats and beluga whales along the Saguenay Fjord in Anse de Saint‐Etienne, Quebec, Canada, to investigate whether the number of belugas observed at the surface and herd configuration are influenced by the presence of recreational boats. We also examined the temporal and environmental factors influencing recreational boat presence. Our results indicate that recreational boat presence is associated with several temporal and environmental variables but not with beluga presence. The number of belugas observed at the surface did not systematically vary with the presence of recreational boats. However, the number of recreational boats was associated with an increased likelihood of observing changes in distances between groups (i.e., dispersion) within beluga herds. For each additional recreational boat present, the odds of a change in herd dispersion increased by 18%, rising from a predicted probability of 31% with no boats to 92% with 20 boats present. Such disruption, potentially driven by both the physical presence and acoustic disturbance of boats, may reduce communication efficiency among belugas and lead to the interruption or alteration of ongoing behaviors. These findings highlight the need to consider recreational boating activities in conservation strategies for the St. Lawrence population of belugas, particularly when managing human use of critical habitats during sensitive periods.