Cetacean Observations and Survey Effort During the TEMPO IN2021_V01 Voyage

This record describes cetacean line-transect observations collected during the Marine National Facility (MNF) RV Investigator research voyage IN2021_V01, titled “Quantifying krill abundance for krill monitoring and management off the Australian Antarctic Territory.” The voyage occurred from Hobart (TAS) to Hobart between 29 January and 24 March 2021 (AEST) as part of the 2021 TEMPO (Trends in Euphausiids off Mawson, Predators, and Oceanography) survey. While TEMPO’s primary objective was to estimate krill biomass and understand predator–krill overlap, dedicated cetacean observations were undertaken throughout the voyage to support monitoring of cetacean distribution and abundance.Four trained observers conducted line-transect distance sampling from Deck 05 using naked eye and binoculars (Fujinon 7×50 and 25×150), with a data recorder on the bridge logging effort, weather, and sightings in PAMGUARD. Observations were maintained during daylight with sea state ≤6, and continued from the bridge when conditions were poor.Combined effort included 3,612 km of formal line-transects, 153 km of informal Deck 05 effort, and 1,115 km of bridge-only effort, yielding 621 sightings of approximately 1,609 cetaceans. Humpback whales were the most frequently observed species, followed by fin whales. Non-cetacean sightings (e.g., seabirds, pinnipeds) were recorded opportunistically.