Humpback Whales in the GBR – spatial habitat modelling

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Researcher:

Joshua Smith PhD

Humpback whales in the Great Barrier Reef

Humpback whales off the east coast of Australia can be sighted throughout the entire Great Barrier Reef from June through to October and yet their breeding area/s have been poorly defined. We have a very good understanding of the migration timing of the whales along the coast, although have a poor understanding of whether there are clearly defined wintering areas for breeding and calving. The large size of the GBR has prohibited dedicated surveys of humpback whales to understand their distribution at a regional scale. Consequently a GBR humpback whale research plan was developed to address this problem.

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MAJOR COMPONENTS OF THE RESEARCH PLAN

Component 1: Review of existing data of humpback whales in the GBR and development of a spatial habitat model

Component 2: Validation of a spatial habitat model using aerial surveys

Component 3: Quantitative assessment of human interactions with breeding humpback whales in the GBRWHA

Component 4: Social behaviour of breeding humpback whales in the GBRWHA

 

Why is this Important?

The population of humpback whales off the east Australian coast (IWC substock E(i)) were hunted to near extinction in the 1950’s and early 1960’s, but since the early 1980’s has been undergoing a rapid rate of increase in population size of approximately 10.9% per year. There has also been a recently rapid increase in port development and associated shipping activity due to mining and industrial activity along the Queensland coast. The rapid increase of both the humpback whale population and human activities within the GBRMP means an increase in human interactions with breeding humpback whales is inevitable. It is critical to know the distribution and habitat use of humpback whales on their breeding ground in the GBRMP to effectively manage these interactions during the important breeding activities of mating and calving.

 

Habitat Modelling of Humpback Whale Breeding Grounds

Collaborators:

Professor Ken Pollock
Dr Sharon Hedley

Background

The migratory corridor of Breeding Stock E(i) (Eastern Australia) humpback whales is well known and has been regularly surveyed since 1981, however, the breeding grounds of this population has been poorly defined. The breeding ground is generally considered to occur within the Great Barrier Reef World Heritage Area, predominantly south of latitude 21°S. Identification of their mating and calving area/s is crucial for appropriate management and regulation, particularly considering the increase in port and coastal development within the Marine Park. Determination of the breeding grounds within the GBRMP, however, has been difficult due to the large size of the area, effectively prohibiting broad scale aerial surveys. This project collated and analysed existing sighting data from various sources to assess the distribution and relative abundance of humpback whales in the GBRMP and develop a predictive presence-only spatial habitat model to identify important areas

breach2

 

This project had three objectives:
  1. Collate contemporary data on areas of high concentrations of humpback whales in the GBR,
  2. Develop predictive spatial habitat models to identify potential reproductively important habitat within the GBR, and
  3. Assess whether using incidental sighting data and spatial modelling are effective and accurate decision support tools for identifying important breeding habitat areas and can help to direct future survey effort to identify critical breeding habitat for humpback whale Breeding Stock E(i).

 

Outcomes

Predictive spatial habitat models were derived using topographic, geophysical and remote sensed data along with occurrence data of incidental sightings of humpback whales from three independent datasets; 1) Border Protection Command (BPC) aerial surveillance program sighting data (1982-1996 & 2003-2009) 2) GBRMPA Eye on the Reef Monitoring Program (2007-2008) and 3) Dwarf Minke Whale Tourism Monitoring Program (2003-2008). The BPC sightings were derived from a systematic aerial surveillance program whereas the two other datasets consisted of incidental sightings from boat-based reef tourism dive operators and were strongly spatially biased. The BPC data (systematic incidental sightings) had adequate spatial coverage throughout the GBRMP and produced a more reliable predictive spatial habitat model for humpback whales than those derived from the two other datasets and was used to produce the final model. Nevertheless, the two other datasets were important in developing the model by informing on the most suitable time periods for which to develop the models.habitat models

The resulting predictive spatial habitat model identified suitable breeding habitat at an ecosystem scale. The model indicates that most of the suitable breeding habitat (> 0.5 environmental suitability value) occurs south of 19°S. Two main areas in particular have been identified: 1) approximately east of Bowen south to Mackay and 2) the Capricorn and Bunker Groups of islands and reefs approximately 100km east of Gladstone. That habitat model was validated using the movements of humpback whales satellite tagged in 2009 by the Australian Antarctic Division and supports the output of the habitat model. It was recommended that a dedicated aerial survey of humpback whales should be designed based on the areas identified in the model for further model validation and to refine our understanding of the extent of the breeding grounds of humpback whales off the east coast of Australia.

Maxent model

Relevant publication

Smith, J.N., Grantham, H.S., Gales, N., Double, M.C., Noad, M.J., Paton, D. (2012) Identification of humpback whale breeding habitat in the Great Barrier Reef. Marine Ecology Progress Series 447:259-272 doi:10.3354/meps09462

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