Howies Scuba

 Marine Life Identification Perth WA

Shore Diving


Crustaceans (Crustacea) form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to the Japanese spider crab with a leg span of up to 12.5 ft (3.8 m) and a mass of 44 lb (20 kg). Like other arthropods, crustaceans have an exoskeleton, which they moult to grow... (Wikipedia) 


Red Bait Crab aka Red Rock Crab

(Plagusia chabrus)

The Red Bait Crab likes to hide on the jetty pylons at Ammo, they seem quite shy little crabs, get too close and they will move away and keep their distance.

In my experience you wont see these moving along the sea bed very often, but if you do and you disturb one, they can move pretty fast.

Generally you will find they are inconspicuous on the pylons and its usually not until you are right on top of them you notice them, usually when they move.

 Blue Manna Crab aka Blue Swimmer Crab

(Portunus pelagicus)

Happy friendly little crabs the Blue Swimmer Crabs... I joke.

They can be quite aggressive, get too close and they will jump up and hold their own.

I have duelled with one of these at Robbs Jetty, it was a big thing, maybe 40 - 60 cms across, and it came right at me.

I am unsure if my Buddy Stevie G had disturbed it or something but it flew at me and I had to use the camera to shoo it away.

They move fast and swim even faster, at first I did not realise what it was, just this dark shadow hammering it through the water. It only lasted for about 5 seconds and with hindsight it was all very amusing..... once my heart stopped pounding.


  Large Male




Carrying Eggs

Photograph taken on a night dive at Ammo Jetty, hard to truly find out what was attached to this Blue Swimmer because as soon as you got close enough it darted off however, it looks like a large Isopod.

Three-Spotted Crab aka Red Spotted Crab
(Portunus sanguinolentus)

A HUGE "Thank You" to Christian D'Abrera for correctly identifying this little beauty.

Photographed on a night at Robbs Jetty, in a couple of meters of water on exiting the dive.

 Pink Swimmer Crab

(Portunus Tenuipes)

I have only seen Pink Swimmer Crabs during night dives, I am unsure if they are nocturnal crabs or not. They are quite small and tiny compared to the Blue Swimmers. These photographs taken at Ammo Jetty 

Sea Toads

Red Sea Toad
(Schizophrys aspera)

Pronghorn Decorator Crab
(Schizophrys dama)

NOTE" Originally I had these following crabs as Schizophrys aspera, however after further investigation I have found out that S. aspera has an evil twin.......not really evil or a twin, actually a very similar looking cousin. Apparently the only way to distinguish these two is to check out  the rostral horns...... in a nutshell I didn't so I cant be 100% certain if its one or both covered here.

Again Ammo Jetty appears to have an abundance of Crustaceans. The Sea Toad in the top column was seen there, difficult at first to notice due to the sponge covering over its carapace.

In two years of diving I had only seen this crab on one dive and that was at Ammo Jetty, then completed a night dive at Boy in a Boat Reef and this stunning example was clinging on to the reef, third row.

If I remember correctly would of been approx. twice the size of the one seen at Ammo Jetty. You can see in the photograph on the right, my finger just poking into the shot so as to give some scale to this perfect example of a Sea Toad.

In late 2013 early 2014 saw a lot of these crabs at varying dive sites around Perth, the central set photographed in the river at The Coombes Reserve.

Paranaxia serpulifera

Next two crabs photographed at Robbs Jetty, so well disguised.

Another member of the same family as the Sea Toads (previous). These are a lot larger than the previous two, massive in fact by comparison.

When I first saw these I thought they were larger version of the Schizophrys aspera, and actually for a while added them under this.

This thing is tiny, I am thinking juvenile Paranaxia serpulifera, but I could be wrong. Mel Turner, Swan River.


Decorator Crab (unknown type)
I am not 100% sure which type of Decorator Crab these are.

I had never seen these type of crabs in 5 years of diving as I write.

I was talking to a friend who showed me her photos of one she saw down under the Busselton Jetty as I was due to dive there in a couple of days.

Anyway that night I completed a night dive at Ammo Jetty and what do you know, I stumble into my own Decorator Crab.

Then dived Busselton Jetty the day after and bumped in to the one my friend was talking about.

These things are weird looking, very menacing, freaky.
Ammo Jetty

Busselton Jetty

Again another unknown type of Decorator Crab, this is purely due to the shear amount of covering this little dude has piled on over its body. Photographed on a night dive @ Ammo Jetty.

Wilsons Sponge Crab
(Dromia wilsoni)

This little orange ball of Jetty Octocoral caught my eye when I saw it moving oddly to the direction of the current or surge flow, so I had to take a second look and, to my amazement under it was a tiny pair of eyes and lots of legs scrambling for cover.

Couldn't believe it when I got home and reviewed the days photographs that I had forgotten to check the camera settings and all I had was blurred images.

Luckily for me I was down at Ammo Jetty the following day and managed to find me another.

How cool are these.

 Bristled Sponge Crab
(Austrodromidia octodentata)

Photographed @ Ammo Jetty.

I have to say I am a little bit gutted I didn't take a moment to check this out properly, vis was a bit poor and we where on our way out from the site and I just swam past and hit the shutter button a couple of times as I thought it was some debris, which is more obvious from other photos I have.

Possibly Xanthoidea Family

Smooth Pebble Crab
(Bellidilia laevis)

Tiny and well camouflaged are Smooth Pebble Crabs. Taken on night dive at Ammo Jetty, I nearly missed it, my light just caught the corner of it and I had to double check just make sure. If I remember correctly as soon as I approached, it buried itself in the sand.

You can see in the left hand photograph my hand which gives some scale to the smallness of these crabs.

This one was photographed at Ammo Jetty.

Granulated Pebble Crab
(Leucosia pubescens)

How lovely are these..... I hope they are making love and not war.

Great photos from my great buddy Mel Turner, taken on a night dive at Robbs Jetty.

My contribution, photographed on a night dive @ Waikiki Beach.
Swift-Footed Crab
(Leptograpsus variegatus)

Photographs taken at Ammo & Bulk Jetty.

A very funny moment at Bird Isl @ Cape Peron. The cave was pitch black and all I could see was these luminous legs crawling across the darkness. So It sees me and decides to hide behind the thinnest piece of rock it could.... "You glow in the dark for crying out loud".

Technically not a shore dive but wanted to include this due to colour variation and a great little story.

Possibly Surf Crab
 (Ovalipes australiensis)

I was not so much concerned with the naming of this crab as I was with what happened with it.

The first photograph was taken at Bulk Jetty and the others where taken at Ammo Jetty, where this event happened.

I was completing a Solo Dive and really getting into all the nooks and crannies when I noticed this little guy buried and hiding away in the corner.

I moved in, took a photograph, and as I tried to get in even closer it was at this point something strange happened, the crab pushed this white mass half way out of its mouth. At first I wasn't too sure what was happening, but it dawned on me that it appeared to be baring its eggs.

I know some crabs will brood their young in their mouths but I am unsure this one of them.

I don't know if this sounds silly or not but I felt it was done with a sense of fear and desperation, as if to let me know it was carrying young, it was very strange and again as weird as it sounds it kind of touched me, so at this point I just left it to its own devices and swam away feeling some how very connected to this tiny little thing.

Knowing my luck someone in the know will inform me it was about to abandon its eggs as a sacrafice and selfishly save its own skin.

Australian Craylet
(Galathea australiensis)

The Craylet was not purposely photographed and was only noticed at home when reviewing the days dive. 

 Rhinoceros Crab
(Hyastenus elatus)

Rhinoceros Crab was a little gem of a find, at the end of Ammo Jetty sadly my photographing skills weren't and this is a poor substitute to how brilliantly decorated this crab was.

4 years later I thought I had achieved it.... thought I had the perfect picture... just looks like a pile of sponge. Even the video didn't turn out....... bloody rubbish.

Taken at Woodmans Point Groin.

Finally some nicer shots or this crab.... I do sometimes look at these things and understandably scratch my head and question I am I identifying these correctly as some of them are so encrusted with so much stuff anything could be under there!!!..... the beauty of that though is who is going to argue about it hahaha......

Purple Antenna Hermit Crab
(Paguristes purpureantennatus)

Photographed on night dive (1&2) and day dive (3&4) at Ammo Jetty.

The first Hermit Crab I believed was making a tapping/rattling sound prior to me approaching it.

I originally had these down as Southern Hermit Crab, almost identical to the Purple Antenna Hermit Crab.

Love the colour variation in these photos. Kindly donated by Mel Turner.

Ah my funny little story.... saw this shell lying on the floor at Ammo Jetty, and thought to myself, "that's a bit unusual.... I will have that one".... so I picked it up, checked it was empty and went on about my dive..... then all of a sudden felt this needle or pin prick sensation in my finger..... checked to see what it was and there was this little fella nipping away at my hand..... very amusing.... obviously I put him back home and all and hopefully no worse for wear...

Western Rock Lobster

(Panulirus cygnus)

Western Rock Lobster..

Small Hermit Crab

(Uknown Type) 

These little guys are tiny and are usually not so obvious when diving.

However they get into absolutely everywhere, once you have noticed one and know what to look for you will see them on every dive.

Photographed at Point Peron Robbs & Ammo Jetty, but I am sure if you take the time you will see them at pretty much every dive site.

I haven't been able to identify which particular hermit crabs these are. I think there are two different types here from the Diogenidae species or left handed crabs.

As always if you have some additional information, dont be shy passing it along.

I have noticed this mass herding of small Hermit crabs a couple of times during night dives, but never during the day,  these taken @ Ammo Jetty, and it just wasn't this one mound, there were a few of these gatherings around the jetty this day. I have no idea whats going on.
Commonsal Shrimp
Photographed at the Kwinana Grain terminal. These are common amongst the Pink Tipped Sand Anemone.

Photographed by Mel T.
Pistol Shrimp
Taken @ Bicton Baths, Swan river, on a night dive.

(Unkown type) 

This photographs was not taken purposely but noticed later on reviewing the photographs.

Slender Shrimp
(Chlorotocella spinicaudus)

These little Shrimp are mad, giving you the firmest of stares and the widest of berths. The moment you try and get close they shoot off like they are on springs, very amusing.

Photographed at Jervoise Bay Woodmans Point.

Southern Mantis Shrimp
(Belosquilla laevis)

Photographed on night dive at Rockingham DT.

Taken @ Bicton Baths on a night dive.
Unknown Mantis Shrimp
Mel T, Swan River.
Western King Prawn
(Penaeus latisulcatus)

I did not realise how fast these things moved, I may even consider taking up prawning, not to eat them but just for fun and exercise, unbelievably fast.

Photographed on night dive at Rockingham DT.

Donated by Mel T after her river dive..... not to eat, just the photos...

Not so fast this one...... just taken straight out of the sand, obviously not awake yet. Photographed on a day dive at Gareenup Wreck North Mole.

Series of photos as it buried itself back into the sand to continue its morning nap.

See some video of the same below.


Little bit of video of a Western King Prawn swimming and then burying itself.

Mysids aka Opossum Shrimps

These Mysids (unknown type) photographed at MAAC.

These are tiny up to 15 mm in length, they are like little flies that swam around you, yet never let you get close enough to swat (photograph).

So I just stuck my camera out as far as I could and snapped away...... thankfully we have plenty of zoom.


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