The Swan River at night has a certain mystique; it’s hard to tell were land and sky meet, the river is so still and the twinkle of the Milky Way is reflected perfectly on the quite surface.


A dog’s bark, the gentle pinging of yacht stays and the indistinct thumping of music and party sounds reach my ears. Standing on a dark bank on the brink of entering the water never fails to sharpen the mind with anticipation. The water is as black and fathomless as outer space.


Whilst others pursue more mundane entertainment and stay rapped in the shroud of everyday affairs, I am about to enter another world, right on their doorstep.


Sound travels a long way over water and the music of another party boat drifts in on a warm easterly wind. Blues if I’m not mistaken, a good omen I decide pulling my mask into place.


However it’s not a melancholy melody that is my focus this night but a tasty crustacean of the same name. Call them Blue Swimmers or Blue Manna or just plain Blues it doesn’t matter; they all taste the same and are a worthy opponent. Armed with long serrated nippers and cranky dispositions these delicious crabs arise from their vampiric sleep as the sun goes down and start to hunt.


None come any larger or tastier than the Swan River variety.


Portunus Pelagicus is a carnivorous, robust swimming crab with a distinct pair of paddles attached to its last set of legs. They have been known to swim up to 20km in a day. The males are a mottled royal blue on top and a lovely china white on their belly. They have a long set of fighting nippers that are a fantastic shade of blue, white and vibrant purple.


The females are more mundane mottled brown topside with a dark triangle on their underside. Smaller nippers and a more chunky body make them distinct from the “Peacock” male.


The female matures at about 1 year of age and is around 97mm across the carapace, spawning takes place in late summer. The male can mate with multiple partners and will “ride” the female for up to 10 days!


The female can then store the sperm package for up to 12 months until water temp and favorable environmental factors trigger fertilization. The eggs will be bright orange in the early stages then turn a dark grey before being scattered to the ocean currants and prevailing winds.


She will usually lay her eggs at the mouth of estuarys so the eggs are carried out to sea were there is abundant food.


 Mature Blue Mannas feed on a variety of items; however their diet consists of manly sassile slow moving invertebrates, bivalve mollusks, polychaete worms, brittle stars and aquatic carrion.  Interestingly the life span may be as little as 3-4 years for the Blue Manna.


The largest spread across the nippers I have heard of was around 90cm for a male.


That is truly impressive and would make me think twice about tackling a crab of that size without a pair of stout gloves. Typically the size we normally encounter is around 60-76cm across the nippers for big males.


Slipping into the Swan River I notice the water is deliciously warm and I relax for a moment getting a feel for the current and tidal movement. Flicking the on switch my torch sends a Smokey beam of light stabbing into the gloomy depths. The rocky slope falls away quickly and my light is ineffective in going any further than 3-4 meters.


It must be said that if diving at night a float with dive flag and red flashing LED is a basic requirement. I use a modified bike light that I have siliconed up to make water proof. This attaches to my ronstan float and works a treat. Also a lumo stick on the snorkel is a must as it makes you easy to spot on top and under the water. Keep a sharp lookout for boats and ferries and stay out of boating channels and yacht clubs.


 Following our dive plan we kicked steadily out into the river, making our way towards deeper water and some good structure. It’s important to have a dive plan before entering the water, especially at night as you can lose sight of each other in seconds.


It was almost a race out to the best ground, no time to relax and breath up, just a deep breath and down into stygian blackness, the seconds and meters tick by until the silty bottom is revealed at about 7meters.


Cocooned by my wetsuit and the darkness I scan the bottom, the narrow beam of light my only focus. The landscape is undulating and alien, strange looking tube worms flaccidly dangle in the current, their mouths crowded with a ring of anemone tentacles blindly searching for food. Black star fish hug the bottom as if devouring the silt with their spider like arms and bloated toad fish hang suspended over the murk, green eyes glowing dastardly in the glow of the torch.



A big Blue appears astride a female, nippers full extended and looking very pissed off. (As you would be).


They separate at the last moment, my gloved hand pinning the Blue right between the eyes. His nippers flail about and constantly smash and grab my arm until they find purchase on one of my knuckles, ouch!


All around me the hazy light of torch beams flicker and dance, the hunt is on in earnest.


In my opinion the only way to catch Blue Mannas is with a long pair of stout welding gloves fitted snugly over your dive gloves, layer upon layer upon layer. (Didn’t Miss Maud say that?)

A small but bright torch lackey banded to your wrist works well as you can go hands free and catch 2 crabs in one dive. Having a backup torch on a belt clip is recommended.


You can either tow or clip a catch bag onto the float or belt clip. I use my home made catch bag for crabs as well as Lobster.


The technique is fairly simple, spot the crab in your torch light and grab him. Go slow until your well within range and then ‘POW’ grasp him firmly by the body. If he takes off then chase him hard as he will turn on you and have a go, when he comes at you with his nippers flashing like propeller blades just take him on. (Wearing a pair of manly welding gloves makes you feel invincible)


One other technique is to use a length of wood about 2 ft long that fits well into the palm of your hand. When a crab is spotted you deftly hold the crab down with said wood while grasping him from behind. This works but isn’t nearly as quick or effective as gloves.


The three best secrets for finding Big Blues.



Cooking crabs is easy and as a general rule 12minutes sees them done.

Bring your water to the boil and add salt and vinegar to taste.


Drown your crabs in fresh water or put them to sleep in the freezer before popping them in the pot. The minute they go in start the timer, when ready drain them off and pop them in icy cold water for 2-3min to stop them cooking. Every one has their own theory but when you consider prawns take about 5min and Lobster about 15-17min then naturally Crabs fit somewhere in the middle.


How do I know? I am a seafood specialist with Kailis Bros and have 20 years experience in seafood. I have cooked thousands of Crabs and Lobster as well as prawns.


Eating crabs is just as much fun as catching them, simply use the end of a leg to pry open the V shape hatch on their under belly and flip the top of the crab off. Remove the ‘dead mans fingers’ or gills and give a quick rinse. Snap the body in two and place on draining board. Crack the nippers just behind the elbow and pile all the pieces onto a huge plate.

Place onto the table with finger bowls, vinegar, salt and pepper.

Get stuck in.


It’s a tradition with the gang to drop by the bottle shop and purchase a couple of King Browns, one each, and to enjoy them whilst devouring the Crabs.


Bon apperteat and happy hunting.


Paul Mckeown