Tag Archives: Seastars

Have the invading Seastars been discovered by a mortal enemy?

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Today I watched a family of Dominican Gulls at Howrah Beach on the Derwent River.

When the temperature rose, I meandered off towards the Derwent River beckoned by the thought of a peaceful walk along a beach (albeit one that I walked on an earlier stage of my trek from the mouth to the source of the River). By the time I reached the end of Bellerive Beach I was feeling very good about the world and so I continued around the point and down onto the people-less Howrah Beach.

The only life was a pair of adult Dominican Gulls and their three immature offspring fishing.

Two surprised me.  From a distance I could see that one adult and one immature were active on the sand where the wash of gentle waves covered their feet from time to time. Each had food of some sort which they couldn’t seem to swallow.  How they tried!  When I walked closer, it was clear both birds were playing with exotic Seastars, with their five brightly orange-coloured arms.

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The immature bird played with a tiny starfish, while the adult focused on a much larger version.  While I watched, both birds battled with their prey, sometimes getting it into their mouth then usually it was disgorged immediately. The shape of bird throats and the shape of the food source were seemingly incompatible. Apart from the challenge of five thick arms which are not particularly pliable, the surface of the starfish is a little knobbly, so I could not believe the birds would have any success getting them ‘down the hatch’.

But then my mouth dropped open in amazement. The immature bird suddenly swallowed his Seastar.   Gulp.  And s/he waded off looking for more. Now that was a feat!

You can read more about these invading starfish in earlier postings at: https://walkingthederwent.com/2015/03/31/pacific-seastars-are-multiplying-in-kangaroo-bay/; https://walkingthederwent.com/2014/09/14/northern-pacific-seastars/; and https://walkingthederwent.com/2014/09/05/stage-2-on-492014-mitchells-beach-email-4-of-14/.

After today’s experience, I wonder whether the Dominican Gulls are finding these Seastars sufficiently tasty so that they will seek them out deliberately.  Perhaps these Gulls will become the natural predator to help reduce the Seastar plague on our native species.  But it looks like hard work to me. Not a comfortable swallow.

Pacific Seastars are multiplying in Kangaroo Bay

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Recently when I walked past the Marina at Bellerive, I looked down in horror to see hundreds of seastars foraging across the river bottom. The water was clear so their orange arms were spectularly visible.  Some of these starfish were larger than a dinner plate.

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The white lines in the photo above are the reflections of yacht masts.

I talked about these pests in two earlier postings; ‘Northern Pacific Seastars’ of 14 September 2014, and Stage 2 on 4/9/2014 Mitchell’s Beach of 5 September 2014. The Tasmanian government department responsible for parks (http://www.parks.tas.gov.au/file.aspx?id=6917)  provides information about Tasmania’s 3 unique starfish and acknowledges the damage that Northern Pacific Seastars are doing to our marine life.

Pretty some might say.  Perhaps that is why they are multiplying and limited collection and destruction actions are being taken.

For a split second I thought to throw off my clothes, jump in and start throwing these scavangers onto the jetty. Of course, common sense prevailed:  I could have been overcome with hypothermia.  In addition, I realised there were too many for one person to collect.  Their removal needs a devoted crowd of wet suit clad divers to be methodical and dedicated.  Of course the sadness is that thousands more are grazing out of eye shot.  And they continue to breed so well in these cool waters.

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You can read Louise Goggin’s story on these marauding seastars at http://www.abc.net.au/science/slab/starfish/.  ‘Enjoy’ the photo in this article “Community divers pulled 30,000 sea stars from the Derwent River in 1993 and hardly put a dent in the population”.

Stage 2 on 4/9/2014 Mitchell’s Beach Email 4 of 14

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The roadway above Opossum Bay beach being narrow and without public footpaths meant it was important not to day dream and for me to be vigilant for the occasional car.  But Opossum Bay is a relaxed seaside village and even cars seem to move sedately.

I continued walking on the road from Opossum Bay beach until I reached a 50Km hour sign for cars, then I moved left off the road onto a well-trodden narrow track through a clutch of Casuarina trees and walked down to the next beach – Mitchell’s Beach. When I checked my watch, only 20 minutes had passed since I had left the bus. Yet already my head was filled with ideas and new information, and my heart was open with joy. The pleasure of walking in clean clear environments cannot be underestimated.

The winding track from the road finished on the sandstone rocks. After an easy few movements and a short distance, I walked onto the sand of Mitchell’s Beach. As I padded along the beach, a gentle breeze whispered across my face while the water lapped quietly onto the sandy shore. Silver gulls wandered around. Opened mussel and oyster shells strewn along the beach, were blanching in the sunlight. I marvelled at the various seaweeds thrown up at high tide, at the decaying ribbons of sea grass and at the fish eggs collapsed like bizarre multi-shaped condoms. The air was rich with the sweet and salty smell of dying seaplants. The water a soft greeny grey. Blissful.

When I come across a few bright orange starfish on the edge of the tide, I cartwheeled them into the dry sand at the upper edges of the beach. I was simply doing my tiny bit to reduce the infestation of these seastars (http://www.abc.net.au/science/slab/starfish/) as devastating invaders of our local marine environment.

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From Mitchell’s Beach I looked directly across the Derwent River and could see the suburbs of Kingston and Taroona with the Alum Cliffs below Bonnet Hill between them. Strikingly, Taroona’s Shot Tower stood tall.  Stunning.

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A pair of footprints impressed in the sand let me know that someone had walked the beach earlier.

Mitchell’s Beach was edged with three to four metre high dunes with tussocky grass on top, which were gradually crumbling into the beach. Demarcations between dirt and sand strata were clearly visible. Towards the northern end of the beach, small seas of water smoothed grey stones provided a separation layer between the beach and the dunes.

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A lone Dominican gull with his pure white tail, pale grey legs and small yellow bill flew off leaving me in charge of his beach.

I reached the end of Mitchell’s beach 40 minutes or so after setting off from the Opossum Bay shop. Again a rocky headland stopped me continuing but I couldn’t see a defined track up the hill onto the land at the top.  Clearly people had found a way judging from a mishmash of bits of tracks.  I chose the least steep section and was surprised when after my first steps up I slid back down. The previous day’s rain had kept the ground lush and damp, and it was clear that the soil included slippery clay. By a more careful choice of foot placements, I eventually reached the top.

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