Backyard Aquaponics
A place to discuss aquaponics

Blue Crab, that sounds interesting for a Texas AP system, so i started a thread...... are they cannibalistic...? what water temps...?

the fresh water prawns are very cannibalistic, and thus i don't have a good place for them ATM

I wasn't aware blue crabs could survive in fresh water, but doing a little research on the internet showed otherwise. Apparently they need saltwater to reproduce though. I couldn't find a source for baby blue crabs though. Do you know of a source?

Roy

No i dont, Shelger sp posted about it on the other thread, so i started this thread, and he has not replied yet.......

but sounds very interesting if they are not cannibalistic and if one can get babys......

I have been looking at some crabs for my sump. Our local crabs are easy to catch but I would never have thought about eating them but apparently they are quite good. Wish we has yabbies or similar in South Africa...

Unfortunately they are canabalistic, especially after a shell molt. In FW pond culture you usually get 10-20% survivability (20% considered good). I am in Florida and we can buy them by the bushell on the east or west coast for pretty darn cheap (they catch and sell them for bait). They do grow extremely quick though.

Sorry, late in replying! Thanks, RS_ for starting the thread, but at the time you did all of my blue crab had valiantly slain each other in aquatic fratricidal warfare.

Yesterday, however, I stopped by the "Super H Mart" in Carrollton, TX, and honestly I was not looking for blue crab since their fish department had previously told me that they never carry it, so imagine my surprise when they not only have a large bin full of them, but since it was early in the day they were all in pretty good shape! My previous attempt with crab had started with beat-up stock, but these guys looked great. So naturally I bought some (16).

I lost 4 overnight - one I was certain I was going to lose by late afternoon (I ended up cooking him to feed to the tilapia), and three others - two of which were a surprise, but I don't think they got enough water.

Here's what I threw together in a huge hurry yesterday as I was losing my light:

I took a 275 gallon IBC tote that was nearly full of water I'd been aging, threw a fountain pump into it that was hooked to a garden hose. I then placed on top of the IBC a clean old shower pan that a neighbor gave me when he was remodeling his bathroom. I ran the hose up through the drain, and through some 2-inch pipe fittings and a gasket so as to create a roughly 2.5 inch stand pipe. I then isolated each crab into an individual plastic bucket (having punched many, many holes in them for circulation) and placed them in the shower pan. That worked fine, but only gave me room for eight buckets.

I then took an old child's sand-tray / water play table thing (I don't know its proper name), that is this big rectangular thing made out of HDPE plastic and comes equipped with a drain, and set it on top of my first layer of buckets to create a second level. By now I'm working from atop a ladder because frankly I'm not a professional basketball player.

The sand-tray thing (I don't have sand in it, that's just what it is made for) comes equipped with a center umbrella holder molded into the plastic, so I stuck an umbrella in it, thinking they'd need the protection come the day, and I tied down the umbrella tines with hospital oxygen tubing (my wife's a nurse, so I get a bunch of that stuff for free, every time they change vendors they discard their remaining inventory).

I ran the hose through a sprinkler head, and have anchored it facing down into a black plastic planter so that aerated water flows out into the 2nd level, down the sand-tray drain into the shower pan, and through the stand pipe back into the IBC tote.

This morning the entire odd structure was still functioning fine. As I said, I am down a few crabs, but that's not a huge surprise. You'll notice that I have not included any filtration at all, so you can probably guess what I'll be rigging together this evening.

Please wish me luck, and any advice, tips, and/or pointers would be greatly appreciated.

If you want them to live, make some structures so they can hide. When one molts, he's a gonner unless he can hide for a bit and let his new shell harden.

I have each crab isolated so they can't get at each other.

However, I had a very high mortality rate today, and since these crabs started in much better shape than the last batch, but largely didn't last anywhere near as long, I suspect there's something wrong with the water in that IBC, or perhaps I didn't clean it as well as I thought.

I'll see if I have any remaining survivors in the morning, but alas - right now this experiment isn't going well.

Hey guys & gals... we don't mind signature links that are related to aquaponics....

But you two seem more like miserable spammers than genuine aquaponicists...

They dont seem to be with us anymore Rupe

I did some additional research and reading on the art and practice of farming blue crab. Everything looked good, so I went and got my third batch of crab - about a dozen or so this time - to try again.

I know the water quality I have is fine - right on the money, supplied with plenty of oxygen and already supporting bountiful and varied life - and I made sure that the crabs I picked out looked healthy and were all feisty fighters who had only been out of their shipping box for a few minutes.

It didn't matter.

Twelve hours after introducing them into their new habitat... all dead.

They didn't bother the tilapia or crawdads, nor were bothered by them in return, they just ceased living, one by one. They didn't even die in combat like my first batch. The final two seemed like they'd be OK, and were still moving around at roughly the 8 to 10 hour mark, but by 12 hours they too were gone.

I love blue crab. But I'm done with trying to raise them until I either have an astonishing (and verifiable) epiphany, or some hands-on tutoring by someone who's got their own ongoing and successful crab farm.

Shelgeyr,

I have not had the chance to try my hand at raising blue crabs as of yet, I have however been keeping and selling them for bait. From what I have researched blue crabs require a minimum of 0.3 ppt salinity to survive, you did not mention the salinity levels in your post I would check those first. It is also possible that they came from higher salinity waters (especially if they are females) and would need time to adjust to the near fresh water tanks they were going into. If it was me i would set up an aerated holding tank at near to seawater salt levels, around 30 ppt, and slowly add water from the system they are going into.

Best of luck.

Thanks for the info Pocketlint and welcome to the forum

Love seeing old threads being dug up.

Blue swimmer crabs.... I'am in heaven with a plate of them always bought already dead though.

It is entirely possible I did not have the proper salinity, however most of the crabs died in combat in their own blue crab civil war rather than simply expire on their own.

If I try blue crab again, however I will make certain the salinity is correct first. My main issue then becomes "what sort of plant that's worth cultivating can put up with and/or thrive in that salinity?"