Leafy Sea DragonLeafy Sea Dragon

Jenni and I had a few days R and R at Port Lincoln this week so I took my gear, hoping to get a few dives.

The shore/jetty dive prospects and viz at Whyalla, Cowell, Port Neill and Arno Bay varied from poor to “possibly just o.k. but let’s try the next town.”

Finally at Tumby Bay, the last town before Port Lincoln, both the viz and the jetty access looked adequate so in I went, complete with a ‘Seachange’ Shark Shield electronic device kindly loaned to me by Mike Wescombe-Down of the Coastal Waters Dive Club. (I wore this shark repellant on all the three dives on this trip and whether wearing a dry-suit or wetsuit I found it simple to wear, very light and compact. It is a vast improvement on the old POD version and I especially valued the reassurance it provided while diving solo in what was for me new territory, at Tumby Bay at any rate.)

Right under the very convenient entry/exit platform midway along Tumby Bay jetty I almost landed on a very beautiful Leafy Seadragon!

(If you were surprised then I bet the Leafy had a few unprintable thoughts!! – Ed.) This was a good omen as the site turned out to be surprisingly interesting. The water was clear, there was comparatively little rubbish on the bottom, and minimal surge made photography easy. Most of the bottom was heavily carpeted with very healthy seagrass; mainly Posidonia australis, with only a few patches of sand, old pylons/crossbeams and clumps of green and brown algae.

The Leafy hung around a big clump of brown algae, which included scaberia, cystophora and sargassum, whereas only two metres away two Shortsnout (short-headed) Seahorses (Hippocampus breviceps) resided in some Caulerpa obscura.

Well, at least one did – and it was only because its pale brown body was so obvious against the rich green of this algae that I spotted it at all. After taking pictures of this female for some minutes I belatedly discovered its larger male mate resting in more typical cryptic fashion among ‘matching’ brown algae nearby.

This reminded me of an experience by Thierry Laparousaz (Collection Manager, Marine Invertebrates, SA Museum) on our March’02 collecting expedition at Western River Conservation Park, KI with Jim Thiselton, Karen Gowlett-Holmes et al.

Thierry was surprised to see a pair of Shortsnout Seahorses riding in a detached clump of brown algae drifting past as he did his safety stop at 3 metres depth. Luckily for these cute little syngnathids, being true fishes they did not warrant collection, as this was a dedicated marine invertebrates collecting trip!

Now, back to Tumby Bay – what else did I see?

Some lovely little light-green leatheries, species uncertain, foraged over the posidonia and I hope to get an ‘ID’ on these when I collect the slide images this week. (possibly juvenile bridled leatherjackets?) Some very approachable pencil weed whiting displayed an attractive lime-green colouration as evidence of their ability to change colour to suit their background, and a very inquisitive yet typically shy blue rock whiting (Haletta semifasciata) repeatedly slipped surreptitiously beneath the seagrass canopy so as to get in close for a good look at this bubbling, noisy and clumsy monstrosity.

The pylons had a reasonable variety of benthic organisms, but nothing to really excite a veteran jetty diver.

This jetty will live in my mind specifically as a great spot to experience, in comfort and good viz, the remarkable biodiversity of its very healthy, indeed positively luxuriant posidonia seagrass ecosystem.

I was not surprised to learn from the foreshore Port Lincoln dive shop that their instructors often take students to Tumby Bay Jetty.

When I get time, in another Newsletter I will tell you a bit about my following two dives under Port Lincoln Jetty – where I took lots of piccies of amphipods, three species of shrimp, anemones, octopi, ascidia, gobies and . . . . . wait for it . . . . . Pentacta anceps! Yes I found two of these gaudy holothurians, sometimes called the Candy-striped Sea Cucumber, and although they have a well-documented distribution from subtropical W.A. around to western S.A. I hadn’t seen them before so I got quite excited.

But, as MLSSA members well know, there’s always something new to get the juices flowing under any S.A. jetty.

Oh, and after one of these Port Lincoln dives, who should rock up for a friendly chat but one Barry Davis, a colleague of Mike Wescombe-down from the Coastal Waters Dive Club.

It’s a small world, eh? – especially as he recognised Mike’s Shark Shield. Just as well it really was borrowed, not misappropriated! Hmmmm. . . .

By David Muirhead

David is a long-serving member of the Marine Life Society of South Australia. He has dived and snorkeled in South Australian waters for around five decades and has a particular interest in bony fishes. David has made the greatest single contribution to the society's Photo Index of local marine species.

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