We’re using statistics and observation data of whale numbers from ships and aerial surveys to better estimate Southern Ocean whale populations for conservation management.

The challenge

Assessing impacts on whale populations

It is essential that we gather accurate data about whale populations, so that we can assess the impact on whale populations of factors such as human activities and climate change.

Our response

Surveys and statistics

Our statisticians are working with the Australian Antarctic Division on ways to use observations from ships and fixed wing aircraft to estimate the numbers of whales in the Southern Ocean.

This research is aimed at estimating the abundance and population structure of minke whales and other whale species for the International Whaling Commission.

Ship surveys

Statisticians use the results obtained when whales are counted from research vessels travelling along predetermined lines.

It is inevitable that some whales will be overlooked. This could be because they are far from the ship, travelling in smaller groups or if conditions are rough.

Our researchers have developed new statistical tools for the best estimate of the total population by working out how many whales were missed in the survey, both near the ship and further away.

Aerial surveys

Antarctic minke whale numbers seem to have declined over the past few decades. This could be explained by the number of whales that have been overlooked in ship-based surveys. One theory suggests minke whales may be moving further into sea ice, areas where whale research vessels can’t follow.

To test this, a pilot aerial survey program was conducted in collaboration with the Australian Antarctic Division in December 2008.

Having tested and validated the aerial survey methods used in 2008, the team returned to Antarctica for a two-month period over December 2009 to February 2010 for a full scale aerial survey.

The CASA-212 fixed-wing aircraft used for the study carried five observers and was fitted with video and digital still camera equipment mounted under the aircraft. The team surveyed 55 559 nautical miles of ocean and pack-ice off Australia's Casey station, covering approximately three times the area of the previous survey in 2008.

Over 211 hours of video and 531 000 digital still photos of ocean and sea ice were collected from the 2009-10 survey.

Only 47 minke whales were spotted in 2009-10, compared to 76 in the pilot survey. The decrease in the number of whales sighted, despite a threefold increase in the survey area, could have something to do with thick pack-ice conditions preventing the whales coming deeper into the ice.

This variability also highlights the huge changes that can occur in population surveys in just one year, so it's important that this work is carried on over a long period of time.

The team have analysed the data from both surveys and hope to combine this with ship based surveys to provide a more accurate estimate of minke numbers and find out if the decline is real.

Other species sighted during the survey included killer whales, southern right whales, sperm whales and southern bottlenose whales.

The results

Reliable estimations of whale numbers

By improving the methods used to collect and analyse the survey data, CSIRO and Australian Antarctic Division researchers are providing more reliable ways of estimating whale numbers.

The aerial surveys are also helping scientists better understand the importance of pack-ice habitat to whales, and how a changing climate may lead to substantial changes in the nature and declines in the extent of sea ice into the future.

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