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Blue Whale Study aerial surveys, southern Australia, 2007-2012
Citation
Gill P. 2015. Blue Whale Study aerial surveys, southern Australia, 2007-2012. Data downloaded from OBIS-SEAMAP (http://seamap.env.duke.edu/dataset/1281) on yyyy-mm-dd.
Contact: Gill, Peter

Access data
Archived data
Availability: Creative Commons License This dataset is licensed under a Creative Commons Attribution 4.0 International License.

Description
Wind-forced cold water upwelling occurs seasonally along the continental shelf of south-east Australia, where pygmy blue whales aggregate to forage. Seasonality and variability are apparent for both blue whale encounter rates and upwelling, within and between seasons. Here we quantify upwelling variability over 11 seasons (2001/02 to 2011/12) and relate it to blue whale encounter rates. more

Two indices, cumulative wind stress (Intensity) quantifying physical forcing, and surface chlorophyll-a (chl-a) quantifying the ocean’s biological response, revealed variability in upwelling at a variety of temporal scales. Within seasons, upwelling Intensity peaked during February, and chl-a during February–March. Blue whale encounter rate from 52 aerial surveys was modelled against upwelling indices and the climate signal SAM (Southern Annular Mode), at individual survey- and aggregated season-levels, using General Additive Models (GAMs). Survey-level GAMs showed that encounter rate increased with increasing chl-a, and with increasing upwelling Intensity to a point beyond which further increases in Intensity resulted in declining encounter rates. This indicated the importance of productivity, as well as relaxation of upwelling, in producing optimal blue whale foraging conditions. In exploratory season-level models, a strong influence of SAM was apparent, with higher encounter rates associated with positive SAM during the preceding 12 months. Including chl-a improved the model, indicating that both broad-scale climatic signals inherently incorporating environmental variability and uncertainty, as well as more proximal regional factors may influence blue whale occurrence in the study area. Measuring the complex relationships between whale occurrence and upwelling is complicated by the fact that the population of blue whales using the Bonney Upwelling is open, and moves between alternate foraging areas. The findings were interpreted in the context of blue whale foraging ecology in this system.

Scope
Themes:
Biology > Mammals
Keywords:
Marine, Aerial surveys, ISW, Australia, South Australia, Balaenoptera musculus brevicauda Ichihara, 1966

Geographical coverage
ISW, Australia, South Australia [Marine Regions]

Temporal coverage
9 September 2007 - 28 March 2012

Taxonomic coverage
Balaenoptera musculus brevicauda Ichihara, 1966 [WoRMS]

Parameters
Animal sightings, Occurrence of biota

Contributors
Blue Whale Study Inc, moredata creator

Related datasets
Published in:
OBIS-SEAMAP: Spatial Ecological Analysis of Megavertebrate Populations, more

Dataset status: Completed
Data type: Data
Data origin: Monitoring: field survey
Metadatarecord created: 2016-05-26
Information last updated: 2016-05-31
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