Changes in cetacean occurrence in Faxaflói Bay, Iceland, as observed from whale watching vessels

The distribution of animal species is shaped by environmental conditions and their ecological niches. The understanding of these niches is essential for conservation, especially for cetaceans, as cetacean species may adjust their geographical range in response to ecological changes. Long-term data is vital to monitor these shifts and guide conservation efforts. While environmental changes are occurring globally, localised effects on specific species and habitats, particularly marine ecosystems, remain understudied. This gap in knowledge is evident in Artic regions. As key trophic species, cetaceans can act as indicators of potential significance and contribute significantly to the economy of local communities via the practice of whale watching. Iceland, a biodiversity hotspot, has experienced significant warming as part of global climate change, possibly affecting the abundance of prey species. Cetaceans such as humpback whales, minke whales, white-beaked dolphins, and harbour porpoises inhabit these waters year-round and may be affected by such changes. This paper focuses on the bay of Faxaflói in southwest Iceland, utilising semi long-term data (2016-2023) from whale watching tours to discern potential changes in the occurrence of these four species. Sightings Per Unit Effort (SPUE) for the four targeted species was calculated for each month and year. ANOVA test (p<.005) and Tukey HSD test were conducted for humpback whales revealing significant differences in Spue in the years 2022-2017 (p=0.006), 2023-2017 (p=0.003), 2023-2018 (p=0.04), 2022-2019 (p=0.02), and 2023-2019 (p=0.009). Seasonal analysis suggests shifts in SPUE, with increased observations during non-touristic periods after 2021. Results indicate intriguing trends in species occurrence, with a significant increase in humpback whale sightings and a steady decline in mine whale sightings since 2018. The inverse relationship between minke and humpback whales suggests possible competition or distributional shifts. Acknowledging limitations and biases from tourism-centric data collection his study highlights the importance of whale watching records as a year-round monitoring tool. Collaborative efforts between operators and researchers are crucial to enhance data quality. Understanding and addressing the observational changes in cetaceans in Faxaflói is imperative for effective conservation measures in this ecologically significant region.