Tag Archives: starfish

Have the invading Seastars been discovered by a mortal enemy?

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

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”.

Northern Pacific Seastars

A couple of weeks ago, on some of the beaches in the northern section of the South Arm peninsula, I located some seastars (orange pronged starfish) and threw them up onto the dry sand so they could no longer breed and multiply. I recorded that these seastars had infected our Tasmanian waters and were a proliferating pest. Today’s Sunday Tasmanian newspaper has published an article about the seastars’ new enemy: the University of Tasmania’s Diving Club.  Recently members of the club have been conducting a clean out of the waters at Blackman’s Bay (located across the Derwent River from the South Arm peninsula) – and doing so in a more humane way than I was.  Apparently a species of spotted handfish used to be common in these waters but is now rarely seen.  The divers hope that this fish will return once they rid the area of the seastars.

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