MONICET: The Azores whale watching contribution to cetacean monitoring.

The MONICET platform has been running continuously since 2009 as a collaborative instrument to collect, store, organise and disseminate cetacean data voluntarily collected by whale watching companies in the Azores. In the period covered by this dataset (2009-2020), 11 whale watching companies have voluntarily provided data from the four islands of the archipelago where whale watching takes place. The dataset contains more than 37,000 sightings of 25 species (22 cetaceans and three turtles). This manuscript presents the first long-term whale watching cetacean occurrence dataset openly available for the Azores. We explain the methodology used for data collection and address the potential biases and limitations inherent to the opportunistic nature of the dataset to maximise its usability by external users.