Position, swimming direction and group size of fin whales (Balaenoptera physalus) in the presence of a fast-ferry in the Bay of Biscay

Abstract

We analyze group size, swimming direction and the orientation of fin whales relative to a fast ferry in the Bay of Biscay. Fin whale groups (≥3 individuals) were on average closer to the vessel than single individuals and pairs (F1,114 = 4.94, p = 0.028) and were more often observed within a high-risk angle ahead of the ferry (binomial probability: p = 7.60 × 10−11). Also, small groups tend to swim in the opposite direction (heading of 180°) of the ferry at the starboard side (binomial test: p = 6.86 × 10−5) and at the portside (binomial test: p = 0.0156). These findings provide valuable information to improve shipping management procedures in areas at high risk for collisions.