Sperm whale individual exposure to whale-watching vessels in the Azores, using photo-identification

Abstract

Sperm whales are one of the major targets of the whale-watching industry in the Azores archipelago. Under the scope of a major project (Watch It) that aims to determine the effects of this activity on this large-sized odontocete, the present work studied the individual exposure of sperm whales to whale-watching vessels. A total of 2603 photographs were provided by whale-watching companies from Faial and Pico islands (collected in 2017 and 2018). Using photo-identification programmes the referred photographs were analyzed and, from their total, 2467 photographs turned into 750 distinct identifications. The summer months were the periods with highest identifications (both new and resighted individuals). About 78% of the identified sperm whales were only seen once and, within the resighted individuals, a great majority was re-observed with an interval of 1-3 weeks (along one year period). Furthermore, the 6 more frequently resighted individuals were mostly observed in the highest whalewatching intensity area, possibly being members of the same groups or social units. These individuals may be the ones under highest whale-watching pressure and it is essential to investigate further the effects of this activity on them.