queensland Help with ID-ing crab - Brisbane River

[Philippp]

Hi everyone, first time posting 

I would like some help identifying a species of crab that keeps entering my crab pot in Hawthorne 

Photos attached below

When I use to catch mud crabs >10 years ago (exact same spot) they were the large with a greenish appearance, with a paddle like rear leg on either side, similar to the ones sold in all fish markets, but for the past two days I keep getting these ones, no paddle and white under the claw, dark black on the top side

So my question is

- What species are they, are they edible??, and whats the legal size for them? (Only kept catching small ones)
 

All crabs were released 

Thanks in advance

Philip

Edited January 24, 2022 by Philippp
Added extra photo on 3rd day - same type of crab

[ellicat]

Just looks like a juvenile muddie to me. Be interested what everyone else thinks.

[Kat]

I did some research on mud crabs a while ago and found out there were different species.  I will see if I can find the article again and post the link.

[ellicat]

PS  Welcome to the AFO forum.

[AUS-BNE-FISHO]

G'day @Philippp

If I am not mistaken, you should be very careful dealing with those crabs. They are a species of stone crabs that are poisonous to eat and have very strong claws.

I read this sometime ago when researching a few spots in the river. Taken from Brisbane Hooked on Fishing group on Facebook. 

Cheers Hamish

[Philippp]

4 minutes ago, AUS-BNE-FISHO said:

G'day @Philippp

If I am not mistaken, you should be very careful dealing with those crabs. They are a species of stone crabs that are poisonous to eat and have very strong claws.

I read this sometime ago when researching a few spots in the river. Taken from Brisbane Hooked on Fishing group on Facebook. 

Cheers Hamish

Wow! Thanks for sharing this, a bit of a shame that they have been the only crabs found crawling into my pots this past few days 

I hope they didn’t chase off all the edible muddies in the area

[GregN70]

Not all crabs are safe to eatand a few can carry lethal doses of toxins. Most of the toxic crabs belong to the family Xanthidae https://en.wikipedia.org/wiki/Xanthidae which is the most diverse family of crabs in Australia and notable for their black tipped claws. So far, only a small number of species of this family are known to be toxic, but it is a good idea to avoid eating them regardless. These crabs are not truly poisonous and the crabs do not produce the toxins themselves. Some species are not always toxic, so it is likely that the toxins are obtained through the crab’s diet or possibly by a symbiotic bacteria relationship. Crabs have no mechanism for delivering these toxins, such as through a bite or poisonous spines, so poisoning only occurs when people eat the crabs.

These xanthid crabs can accumulate two of the most lethal natural substances known - saxitoxin and tetrodotoxin - in their muscles and egg masses. Both saxitoxin and tretrodotoxin are so incredibly toxic, that as little as half of a milligram is capable of killing an average sized adult. The toxins are also heat stable and will persist in the tissues despite being cooked. Saxitoxin is the primary toxin involved in paralytic shellfish poisoning, which is often caused by people eating mussels or oysters that have consumed toxic algae. Intriguingly, saxitoxin is listed as a grade one chemical weapon under the UN Chemical Weapons Convention and was reputedly used by the CIA in suicide pills. Tetrodotoxin on the other hand is famously found in the Japanese puffer fish, a delicacy known as “fugu” which only the most skilled chefs are licensed to prepare. Both chemicals are neurotoxins, affecting the nervous system, resulting in paralysis by shutting down the nerve cells’ ability to transmit information.

There are a number of known Australian species that may be toxic if eaten, and while some do reach good sizes most are relatively small. While care should be taken for the preparation of all seafood, if you’re not sure what the species is, then the best possible advice is to not eat it.

[Old Scaley]

Scary stuff there. If you are crabbing the river from the bank, I wonder if the muddies might be down a little deeper to find more salt after all the rain recently? Do you get many at Hawthorne generally? Maybe they will come back once the fresh flushes through.