Star Wars: Alien Invasion

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By May Saw

Inch by inch, one foot after another. The predator has found its next meal. Its prey senses the predator but makes no move. With one final lunge, the predator will feast. Suddenly something snatches it out of the water. Above the water, a young woman places the purple and yellow seastar into a bag and continues to search for more.

This is a war between an invasion of ‘alien’ Northern Pacific Seastars, the native Australian marine life, and humans who unwittingly started this war but have no immediate means of ending it.

A volunteer picking up a Northern Pacific Seastar with a grabber.

Scientifically known as asterias amurensis, the Northern Pacific Seastar is a native species of China, Korea, Russia and Japan. First found in Tasmanian waters more than 30 years ago, they have since established a population and multiplied exponentially.

When they were discovered to have spread to Port Phillip Bay in 1995 it was already too late. Presently the number of Northern Pacific Seastars in Port Phillip Bay are estimated to be over 100 million.

A 1998 CRIMP Technical Report describes the Northern Pacific Seastar as “a voracious predator and affects the viability of commercial shellfish industries.”

The numbers and alarming speed of breeding of the invasive Northern Pacific Seastars causes an unbalance in the Australian marine ecology. To these gluttonous invaders, Australian waters are like an all-you-can-eat buffet. They are winning the battle against the native seastars for food and habitat. But the primary victims are the prey.

“Studies have shown some local reef species fail to recognise asterias as a predator, as a result, they do not attempt to escape,” Mr John Ahern explained.

Commonwealth Scientific and Industrial Research Organisation’s (CSIRO) former Centre for Research on Introduced Marine Pests (CRIMP) has strived to find a solution to the Northern Pacific Seastar. Caroline Sutton is one of the marine biologists involved in those studies.

“In the ocean, like on land, introduced species can become a problem in their new environment because they no longer have the natural predators and diseases that normally keep their populations in balance. ” she commented in her research.

To combat this problem, several organisations have literally taken matters into their own hands. Earthcare St Kilda has been running seastar removal events around St Kilda pier monthly since 2001. Volunteers gather at the pier and remove all Northern Pacific Seastars they can find.

Julianne Stuart, a member of Earthcare, has been helping out with the seastar removals for about 5 years.

“On average we have around 10-12 volunteers … Once collected in bags, we take them back to our central location … where they are sorted via size … We count about 50 of each size, weigh them, then estimate how many we have removed,” she explained.

The plastic sheet used to measure the size of the Northern Pacific Seastar before they are weighed.

As the sun reaches its summit, volunteers head back to the pier to unload their spoils of war. Mounds of Northern Pacific Seastars are piled on a plastic sheet used for sorting the seastars by size. They are then weighed, recorded and unmercifully dumped into the nearest bin.

Volunteers refuse to admit defeat in the face of this insurmountable task. They continue to battle in this hopeless war.

“We see it as a thinning process, like weeding your garden at home, even though you know they will come back,” said Ms Stuart.

Amanda Molyneaux, another Earthcare volunteer, witnessed first-hand the sheer numbers of the Northern Pacific Seastar. She recalls how astonished she felt when she saw a myriad of themlined up on St Kilda beach last winter.

“There were Northern Pacific Seastars washed up all along the tide line. Some were trying to get back into the water and their tracks were visible in the wet sand.”

Acknowledging the significance of this problem, Port Phillip Ecocentre was awarded a grant of $20,000 from Caring for our Country for a pest seastar control project. Port Phillip Baykeeper, Neil Blake is in charge of this project beginning from April 2012.

“The objective of the project is to learn more about their (Northern Pacific Seastars) seasonal behaviour in comparable habitats in the south and north of the Bays,” said Mr Blake.

The project hopes to develop the “best practice guidelines for removal and disposal of Northern Pacific Seastars”.

“It would be great for future generations to see the same animals alive, not just in books,” she continued to stress.

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