The importance of a coastal embayment for migrating humpback whale mother-calf groups: characterising movement patterns using geospatial methods

• Main Author: Jones, Alexandra
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Sydney 2023
• Subjects: humpback whale; thermal imaging; resting ground; automated detection; Humpback Whale
• Online Access: https://hdl.handle.net/2123/31781

Humpback whale populations that migrate along Australian coastlines each year have rapidly increased in population size since modern whaling. This population growth has been associated with increased presence and activity of humpback whales in coastal embayments along the Australian coastlines, particularly mother-calf groups who use the sheltered waters to conserve energy. However, growing numbers in nearshore areas also increases the potential for disturbance from Defence, recreational and commercial activities. The disturbance of resting mothers and calves may have longer term implications for calf growth during key development stages. Jervis Bay is a coastal embayment in which increased numbers of mother-calf groups have been observed in the last two decades and is also an area of significant anthropogenic activity. This thesis aims to assess the significance of Jervis Bay to humpback whale groups using novel survey methods. The movement patterns in the Bay are characterised and compared with that observed for humpback whales migrating south offshore. During the peak timing for humpback whales passing Jervis Bay in 2018, 2019, and 2021, land-based, boat-based, and unoccupied aerial vehicle (UAV) survey methods were conducted. Results showed that a disproportionately high percentage of groups entering the Bay contained a calf and that travel of mother-calf groups in the Bay was significantly slower and less directed than movements of these groups offshore. Resting and nurturing behaviour was observed in aerial footage. These findings support the argument for identifying Jervis Bay as a resting ground for mother-calf humpback whale groups of the east Australia (substock E1) population. With improved understanding of their behaviour and movement in the Bay, there is a need to monitor and manage increased anthropogenic activities during the southern migration season.