Southern right whale movements, dive behaviour and threat exposure in southern Australia (NESP MaC 3.15)

Full description

Southern right whales (Eubalaena australis) in Australia are endangered following severe depletion by commercial whaling. Australian southern right whales comprise two partially differentiated populations, a smaller eastern population and a larger western population. Encounter Bay (SA) lies near the geographic boundary between these populations and is a re-emerging calving and aggregation area. However, the population identity of whales using Encounter Bay, their subsequent coastal and offshore movements, and their exposure to anthropogenic threats is poorly understood.

Four southern right whales were satellite tagged in Encounter Bay in June 2024 to investigate migratory movements, connectivity, behaviour and exposure to anthropogenic and environmental threats. The data are provided as (1) raw tracking data containing Argos satellite-tag locations; and (2) locations predicted at six-hour intervals using a state-space model, together with dive metrics summarised for the three hours before and after each modelled location.

Spatial risk-exposure data are provided as rasters representing exposure of the tagged whales to climate change, entanglement, chronic underwater noise, pollution and ship strike, together with cumulative exposure across these threats. Exposure was derived by combining spatial patterns of whale occurrence with normalised threat intensity and is expressed from 0 (no exposure) to 1 (maximum exposure).

Together, these data describe the coastal and offshore movements of southern right whales, and their spatial exposure to anthropogenic and environmental threats across southern Australian waters.

***EMBARGO NOTE*** This data is embargoed until June 2027. Please contact the MaC Hub Data Manager ([email protected]) for access enquiries prior to this date.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: ---Tracking data--- Satellite telemetry data was collected by four non-retrievable SPLASH10-TDR10 satellite tags deployed on southern right whales in nearshore waters of Encounter Bay, South Australia, between 17 and 22 June 2024. Satellite tags recorded Argos locations and dive information during subsequent coastal and offshore movements. For movement analyses, raw Argos locations were quality controlled by removing invalid Argos location codes ("Z"), duplicate timestamps and locations producing implausible swimming speeds. Tracks were divided into continuous segments where transmission gaps exceeded 24 hours, and segments containing fewer than 10 locations were excluded. The resulting filtered dataset contained 6,715 locations. Because Argos locations were irregularly spaced in time, a state-space model (SSM) was applied to the filtered tracks to estimate whale positions at regular six-hour intervals. This produced 1,807 modelled locations across the four tagged individuals. Dive events were defined as submergences to at least 5 m depth lasting more than 15 seconds. Dive were aggregated into six-hour periods centred on each modelled location, representing the three hours before and three hours after that position. Summary metrics included mean maximum dive depth, maximum dive depth, mean post-dive surface interval, mean dive duration and dive count. AllRawTracks_SRW_MollerWouters2026.csv - DeployID: the unique Argos identifier assigned to each satellite tag - Datetime: the date and time in utc with the format 'dd-mm-yyyy hh:mm'. For predicted tracks, locations have been modelled every six hours - Longitude - Latitude - Quality: the Argos assigned location class (see paper for details) AllPredictedTracks_SRW_MollerWouters2026.csv - DeployID: the unique Argos identifier assigned to each satellite tag - stepTime: the date and time with the format 'dd-mm-yyyy hh:mm', locations have been modelled every six hours for the state space model - Longitude - Latitude - Binned Dive data columns contain cumulative dive data from the three hours before and after a modelled location - Dives_MeanMaxDepth: mean maximum depth across all dives - Dives_MaxDepth: deepest dive within the period - Dives_AvePost DiveSurface_Min: mean post-dive surface interval within the period in minutes - Dives_MeanDuration: mean dive duration within the period in minutes - Dives_Count: total dives recorded within the period ---Spatial threats--- Spatial threat layers representing ship strike, chronic underwater noise, pollution, entanglement and climate change were compiled from existing spatial datasets and standardised to a 10 × 10 km grid. Each threat layer was normalised from 0 (no threat) to 1 (maximum threat intensity). Exposure was calculated by combining the occurrence of the four tagged whales within each grid cell with the corresponding threat intensity. Cumulative exposure was derived by combining the individual threat layers and normalising the resulting values. The final raster products contain the five individual threat-exposure surfaces and a cumulative threat-exposure surface, with values ranging from 0 to 1.

Notes

Credit
The data collections described in this record are funded by the Australian Government Department of Climate Change, Energy, the Environment and Water (DCCEEW) through the NESP Marine and Coastal Hub. In addition to NESP (DCCEEW) funding, this project is matched by an equivalent amount of in-kind support and co-investment from project partners and collaborators.