Where are all these crabs from?

I'm sure you’ve notice either the large number of crab shells and carcasses on the beach this summer or more likely you've felt something nipping at your bare feet in the shallow surf. The culprit is the Sand Crab [Ovalipes australiensis]. They are common enough and a favorite food for the pacific gulls. But why so many this year?

Please leave a comment is you think you know why.


A word of warning for the keen surf fisherman from the Museum Victoria, Ovalipes are experts at removing bait from fishhooks!

A good day for a walk

I hope those that braved the walk out around Point Symthe area had a great day. One of the highlights was seeing a pair of hooded plovers possibly at a new nesting site and some oyster catchers resting on the beach.

The experiments with trying to directly observe sand drift, where not totally conclusive (steve may have photos) but overall seemed to show more movement to the north west than south east. This corresponds with the direction obtained by reading the sand bars, which where attached to the beach at the south eastern end.

Photographing the sunset

This time of year the sunsets at Venus Bay can be specular, plus we probably also have the time to sit and watch them. The beach at Venus Bay is actually oriented mainly north south and faces west so you can watch the sunset into the sea. You will be able to photography sunsets over the water equally as rich and warm as those from the famed cable beach in Western Australia (ok we don’t have camels)

Pointing your camera (especially automatic digital ones) straight at the sun however often leads to disappointing results. The main problem is the exposure (the light meter in cameras often get strong contrasty subjects wrong) and photos are bleached out or have a flared out overexposed fussy light burnt into a dark image). One trick is to half press the shutter button pointing while away from the sun (this will get the light meter to correctly read the average lighting) then keeping your finger on the button move back to looking directly at the sun and finally pushed you finger fully down. It may take a little practice but with a digital camera you can view what you just took. Another alternative is to use bracketting (I pretty well always do this now for sunsets). This is a feature on most digital cameras now that will take 3 or 5 pictures at once with different exposures. But there is plenty of other good advice on the net,such as digital photography school and wikiHOW. Sunsets make great personal screen savers/wallpaper on your computer

If you look at my photography blog you will see sunsets are a favourite subject. Here are a few sunsets already in the VBOP group on flickr, perhaps you would like to add more. Lets make Venus Bay as famous for sunsets as cable beach.

Alas the beach one surf life saving observation box is no longer

Surf Diatoms on Beach Four

A small Diatom bloom on Beach Four today (3/1/11) .
Beach Four has signs of undercutting of the foredune. The access path is very steep due to slumping of the dune it passes.
I noted one dead Little Penguin lying on the dunes.
We surveyed the Pipi shells on the beach for a chipped ratio of 10 out of 11 shells. The smallest shell being from a sexually immature juvenile individual approximately 8-9 months old.

Reading the sandbars

Most of the action on the beach at the moment is occurring down at the low tide line. If you look there is extensive development and changes in the sand bars. You can read the direction of the longshore drift of the sand by analysing the sand bars.

Look to find which end the bar is connected to the beach. If this is at the southern end of the sand bar the net longshore sand drift will be going to the north. If connected at the northern end the net longshore sand drift will the going south.

Note: Diagrammatic only & not to scale

The mechanism of longshore drift on a long sweeping beach like Venus Bay is fairly easy to explain. The wave hit the beach slightly obliquely (this depends of ocean currents and nearby coast and sea floor topography) and carry some sand particles up the beach in the same direction that the wave was travelling as it hit the shore. Then the wave receded but now the water runs down the gradient of the beach (ie at right angles to the beach) so some sand is again washed back but following this new flow direction. so the sand particles zig zag up and then down the beach moving them along the shore a little as each wave carries them up the beach.

Very much related to the development of sand bars along the Venus Bay beach are Rip currents. These are feed with water but the lagoons and depressions that form behind the sand bars water coming over the bars has to run along this hollow to get back out to sea. Sometimes it quickly erodes deep gutters (a favourite pace for surf fisherman at higher tides) or pot holes. Often the sand near the deeper pots holes is very loose and unconsolidated because it is recently transported there.

Over the past few years the longshore drift has been dominantly to the south but this year It would appear that the general sand drift has turned to the north. It would be nice if all those interested observed the sandbars and posted their observations of sand drift  as comments here or as messages  on Twitter using the either hashtag #VBOP or to @VBOP

Eg for twitter

@VBOP beach one sand bars show sand drift to north