Move to conserve Bremer Canyon's orcas

November 28, 2016 by Geoff Vivian, Sciencenetwork Wa, Science Network WA
Move to conserve Bremer Canyon's orcas

The jury is still out as to why hundreds of killer whales (orcas) flock to a location above the continental shelf near Bremer Bay on WA's south coast.

A growing band of whale buffs and scientists from across the globe has been flying into Perth, taking connecting flights to Esperance, and chartering a boat to Bremer Canyon.

They go to see orcas congregate in huge numbers above the to feed.

Film maker and charter operator David Riggs discovered the population several years ago and says they are at the end of a that begins with petroleum leaking onto the ocean floor.

Bremer Canyon is long-submerged geological feature comprising the mouths of a river system that existed when sea levels were considerably lower and Australia's shoreline was further south.

While part of the canyon falls within a Commonwealth Marine Reserve the orcas' feeding ground is within an expired petroleum lease and therefore outside the Reserve.

Mr Riggs has been lobbying the Commonwealth to extend the boundaries of the Marine Reserve to include the orcas' feeding ground.

He says a pressurised petroleum reservoir is leaking out somewhere at the bottom of the Canyon and providing food for plankton.

According to his reasoning, larger organisms then feed on the plankton and become food for larger organisms and so on until orcas are attracted to this abundant source of prey.

Marine biologist Colin Buxton, who was part of an Expert Scientific Panel appointed to review Commonwealth Marine Reserves, says this hypothesis has not been tested.

Adjunct Professor Buxton says the review of Marine Reserves included a comprehensive review of existing ecological studies and the orcas' feeding ground has been documented but not studied in any detail.

"While it's not documented in our report we do note that hydrocarbon seepage has been documented elsewhere as being a source of primary productivity around the world," he says.

"There are several places around the world where hydrocarbon seepage is a natural phenomenon and it's a plausible hypothesis that it could lead to that sort of food chain dynamic."

He says an alternative explanation is nutrient-rich water forced up through the canyon by tides or currents.

"Cold water upwelling does drive some of our largest fisheries in the world," he says.

"Cold water is nutrient rich and once it reaches shallower water up onto the shelf it drives a very large productivity cycle which leads to huge numbers of fish."

Whatever the origin of the ' feeding ground, the Commonwealth Marine Reserves bioregional advisory panel recommended it be protected.

Explore further: Scientist: Breach dams to save orcas off Washington state

More information: Full details of the review are found here: www.parksaustralia.gov.au/mari … /review/reports.html

Related Stories

SeaWorld to stop breeding killer whales

March 17, 2016

Marine theme-park giant SeaWorld announced Thursday it will stop breeding orcas, also known as killer whales, and will no longer keep any of the giant sea creatures in captivity after its current generation dies.

Recommended for you

How quinoa plants shed excess salt and thrive in saline soils

September 21, 2018

Barely heard of a couple of years ago, quinoa today is common on European supermarket shelves. The hardy plant thrives even in saline soils. Researchers from the University of Würzburg have now determined how the plant gets ...

Basking sharks can jump as high and as fast as great whites

September 20, 2018

A collaborative team of marine biologists has discovered that basking sharks, hundreds of which are found off the shores of Ireland, Cornwall, the Isle of Man and Scotland, can jump as fast and as high out of the water as ...

Decoding the structure of an RNA-based CRISPR system

September 20, 2018

Over the past several years, CRISPR-Cas9 has moved beyond the lab bench and into the public zeitgeist. This gene-editing tool CRISPR-Cas9 holds promise for correcting defects inside individual cells and potentially healing ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.