Opinions on Marmorkrebs.. blessing or nightmare

Does anyone have any experience or comments on the mormorkreb crays currently for sale in the trading dock?? im thinkin these might make a sustainable food source for my sunfish, shadow bass, and warmouth.

Edited by Uland, 13 March 2009 - 07:47 AM.
Edited Title

Not much experience here, but I would like to comment on the seller's fast and professional shipping. I've only had my cray for a day, but she seems to have settled in well after a long journey. From what I've read they don't seem to be harder to keep than other crays (toss them an algae wafer from time to time, or just add a double handful of dry leaves every 4-6 months, and make sure their tank doesn't evaporate clear dry). I bought one with the intention of using them as feeders too, and it sounds like they should be good for that.

I just tried some small wild-caught crays as food, which I had never done before, and they seemed to go over well. Mummichogs are vicious! One ate a cray that was rather larger than its head.

The downside is that if you start with one it might take 6-8 months to have a really sustainable colony producing at a rate to make up a significant part of those fish's diet, and it may take a good amount of tank size. On the upside, crays are really pretty interesting critters to keep in their own right, so I'd say they're worth a display tank. Eventually you could just put a couple big ones in your main tank and watch them produce popcorn shrimps from time to time

Not much experience here, but I would like to comment on the seller's fast and professional shipping. I've only had my cray for a day, but she seems to have settled in well after a long journey. From what I've read they don't seem to be harder to keep than other crays (toss them an algae wafer from time to time, or just add a double handful of dry leaves every 4-6 months, and make sure their tank doesn't evaporate clear dry). I bought one with the intention of using them as feeders too, and it sounds like they should be good for that.

I just tried some small wild-caught crays as food, which I had never done before, and they seemed to go over well. Mummichogs are vicious! One ate a cray that was rather larger than its head.

The downside is that if you start with one it might take 6-8 months to have a really sustainable colony producing at a rate to make up a significant part of those fish's diet, and it may take a good amount of tank size. On the upside, crays are really pretty interesting critters to keep in their own right, so I'd say they're worth a display tank. Eventually you could just put a couple big ones in your main tank and watch them produce popcorn shrimps from time to time

Thanks , and when you said mummichog, i almost fell outta my chair laughing. a while back a friend of mine who travels to florida and in the south quite a bit saw a little goby in one of my tanks from a distance and asked if that was a mummichog, I said a WHAT, and the argument insued.. me laughing and telling him there aint no such thing as a mummichog . so finally he pulled them up on the internet to prove it, i almost messed myself. Anywho thanks for that second laugh, and if you ever become overrun with mummichog send me a couple

Does anyone have any experience or comments on the mormorkreb crays currently for sale in the trading dock?? im thinkin these might make a sustainable food source for my sunfish, shadow bass, and warmouth.

Honestly many will tell you they're positively frightened by this "cloning" creature for the same reasons you would consider it as a food source. It only takes one in a suitable environment and we're toast. The thought of a crayfish like this getting loose should send chills down your spine and for this reason we must ask ourselves to react before the law kicks in and makes sure we can't keep them. Unfortunately by the time any law kicks in to prevent possession of such a potentially harmful crayfish, it will almost certainly be too late.

I believe animals like this challenge ethics and law, and I would have preferred this thing had never darkened our door.

I have marmorkrebs and they reproduce quickly. I use extras as feeders. I think an ideal situation is a marmorkreb or two in with fish that won't bother the adult, but will eat the babies.

Hey Fish4fun...this title really should be more specific so other members can navigate the forum more easily. Mind if I change it? Do you want to title it yourself?

Hey Fish4fun...this title really should be more specific so other members can navigate the forum more easily. Mind if I change it? Do you want to title it yourself?

Please feel free at any time to change my posts as you deem necessary. I usually have to struggle to come up with somthing for that purpose. And while on the subject, I had the same thought as you did about the self cloning cray, beyond their obvious use as self renewing food source for my fish. Sometimes though the draw backs that you mentioned outweigh the advantages. I think for me at least, i will stick to pellets, so i dont have to feel bad when somebody lets one get loose and they show up everywhere. Maybe we should rename it... Marmokrebs, blessing or nightmare ???

Considering they've already proved themselves able invasives in Europe....I am quite worried about what they will do here. Esp. being sold as feeders it will only be a matter of time before some get dumped.

Yet, I can't help but be drawn to the idea of an easy feeder crayfish.

Exactly, i have always been a lazy hobbyist, lookin for some self sustaining source of food, like in the wild, but until someone like Uland, gives me a gentle jerk of the arm, i fail to see the potential damage that could be done. I think all we can do as individuals is make an informed decision, and as for me its back to prepared foods, because i want no part of maybe messing up our enviornment any more than it already is.

So here's a question right, wrong or indifferent... Someone want to explain to me how a parthenogenic crayfish can isolate a recessive allele? I thought they were clones?

Anyway, here's what Long Hair Phil has brewed up:

 blue_marmokrebs.jpg   21.36KB   3 downloads

Todd

Interesting... I've never really thought of mutationin parthenogenic creatures (even though that's how they got that way). I've always been a little shaky at the finer points of genetics (I like the big picture, and am not a huge fan of strerile labs), but it seems like a mutation would be more likely to express in a parthenogenic organism than one that's sexually reproducing since there is no male set of chromosomes to hide the mutation. Also, mutations might compound with asexual reproduction since there are no new sets of genes being introduced to blood lines to hide, and most likely eliminate in the long run, mutations that are popping up all the time. It's all a game of chance, and Phil was on the money, here. That's a cool looking crawdad.

I don't know about genetic differentiation in populations of Amazon Mollies, but have heard the theory that Amazon Silversides have evolved multiple times on the Gulf Coast between Veracruz and Florida. Now, I'm starting to question that to a degree. With all-female taxa, wouldn't mutations just compound in different, random directions that eventually will have very little resemblance to the ancestral form (in neutral genes, anyway)? Now I'm off topic and rambling, but I've been at Aquatic Biology Society seminars all evening and am all hopped up on coffee. Just too tired to get any real work done...

Anyway, once again, I do like the mudbug.

With parthenogenesis, diploid sets of chromosomes are passed from generation to generation without recombination. But it's true that copying errors by DNA polymerases could introduce changes, either in coding sequences or in regulatory elements. An allele could become relatively recessive by low or no expression through such errors. So strictly speaking "new" alleles can appear even without meiotic recombination. Given that, we then enter the fun world of modeling how such a mutation can spread through a parthenogenic population since we're looking at raw differential survival and reproduction (fitness). Bruce Turner looked at some of these questions with the mangrove killifish, but that species has at least a small percentage of true males appear.

Very interesting. I was talking with one of Stepien's student's today, he was pretty interested in the phenomena and explained this in a bit more detail. But yeah, pretty much what you said Bruce. Thanks!

Now to figure out if anyone else has isolated this, and what ol' Phil might charge on Aquabid if he decides to sell them lol.

Todd

I'd be interested to know what he charges as well.

Maybe on the upside the blue ones will be somehow less viable in the wild.

Very interesting. I was talking with one of Stepien's student's today, he was pretty interested in the phenomena and explained this in a bit more detail. But yeah, pretty much what you said Bruce. Thanks!

Now to figure out if anyone else has isolated this, and what ol' Phil might charge on Aquabid if he decides to sell them lol.

Todd

When he figures it out, let me know. I want one!

I took one of my marmorkrebs to visit the 6th grade science classes at school. I asked the teacher to talk about how important it is to not release animals into the wild. I think they enjoyed it.

Edited by schambers, 10 April 2009 - 04:19 PM.

I recieved this email late last night from a person on a tropical fish-keeping forum. He sent me a copy of this email to the Marmorkrebs website, and their response.
The email:

To whom it may concern,
I have seen a lot about the marbled crayfish on the internet and especially on Craigslist. I noticed that on those posts and on you site you have "Marbled Crayfish are easy to care for as aquarium pets, and are easy to raise in colonies to use as "feeders" for aggressive aquarium fishes, as well as for use as bait in sports fishing. Since one individual can create a colony, it is very easy to establish a limitless supply of feeders and bait animals in a few months time."
The blue part concerns me. As a concerned conservationist, I must tell you that you should NOT be promoting them being used as bait. Bait can survive and be released into our environment and could cause irreversible damage to our aquatic ecosystems. This is an exotic organism and it is illegal to release any exotic into our wild waters. This is how the rusty crayfish (P. rusticus) has spread through the US and is harming the native crayfish populations. Similar has been done with the release of aquarium pets - snakeheads, oscars, cichlids, pythons, etc, etc.

I ask of you, please remove the part about using them as bait. I feel that you should be promoting responsible crayfish-keeping. Please be a part of the effort to keep our native crays and critters safe.
Thank you very much.
-(name)

The response:

Yes we are familiar with hysterical reports in tabloid press that have little basis in fact. The reality is that new species are introduced all over the globe by birds and other natural causes, and any excess crays become a food source for fish, reptiles and more. It is NOT illegal in most states for a reason - there is no danger outside academia.
Nitey nite

The person who sent this copy of the email to me asked me my opinion, but I have yet to answer. And I am unsure how much research he did on the legality of using them as bait... so I don't know...
Anyway, I figured I'd just let yall see what this guy sent me. I am unsure how to respond to this guy.

Edited by UncleWillie, 28 June 2009 - 11:17 AM.

I've given up fighting these battles (although I'm not beyond muttering venomous sarcastic comments under my breath ).

At the regional and state scale, agencies make trouble for citizens, but ignore the shipping, channel "management" and CAFO industries. At the local scale, drainage adminstrators "dip out", introduce gambusia, and ignore livestock wandering on banks and in streams. At the virtual scale, web adminstrators and forum members at aquaria sites give snarky responses bathed in paranoia that invasion biology is only limited to the minds of academicians, and the grant money they're after. Etc ad nauseum. People are going to do whatever the hell they want.

Your energy may perhaps be better spent doing local programs with kids and adults, and any mixture therein. I've had no trouble whatsoever scheduling 5 or so programs per year interpreting WHY the former situations are troubling. In fact, I had to learn how to say "no" for the sake of sanity.

Or take some of those great pictures you're getting and put together a pdf Field Guide to the Fishes of the Little River and have Drew put it on the NANFA site (if you don't want to bother with your own website).

There are many more positive ways to utilize your creativity and energy than fighting with stubborn people. Once society is outraged, then change will come. If it doesn't, you'll have had a much more fluid life talking to people you enjoy talking to, rather than people that you're always fighting with.

That's my 2 Zen cents

Todd

You make a great point, Todd.
When receiving this email, I though to myself, "and what do you want me to do about it?" Yeah, life is incredibly busy right now as it is, and these kinds of things I am not going to deal with - at least not at the moment.

Or take some of those great pictures you're getting and put together a pdf Field Guide to the Fishes of the Little River

Hmm... I haven't though about that. I'd have to get some better pictures of those fast minnows, and have to get a lot more species. Maybe one day!
I am considering making a type of 'scrapbook' of my fish, herps and interesting invert findings from different areas (TN, NC, piedmont GA, coastal SC, FL Keys) just for personal use and showing family and friends.

You always have to remember that carp were introduced into this country with great energy and resources over a hundred years ago to improve fishing, the ecology, whatever. So sure, why not marmorkrebs? People will always believe whatever dumbass thing they want.

When receiving this email, I though to myself, "and what do you want me to do about it?" Yeah, life is incredibly busy right now as it is, and these kinds of things I am not going to deal with - at least not at the moment.


Hmm... I haven't though about that. I'd have to get some better pictures of those fast minnows, and have to get a lot more species. Maybe one day!
I am considering making a type of 'scrapbook' of my fish, herps and interesting invert findings from different areas (TN, NC, piedmont GA, coastal SC, FL Keys) just for personal use and showing family and friends.

Right now isn't always the best time, even to do the positive things. That's part of where I've had to learn to say "no". Sometimes it's hardest when some toolbox like this crosses paths, sometimes its when you see a bunch of urban little kids aching for a positive interaction with nature. I don't profess to have even come close to mastering this

Just keep taking pictures, man. At some point, you're going to go "Wow, I have a lot of pictures" and then it's a matter to just fill in the gaps.

And if you can spare an afternoon or a Saturday to take some kids snorkeling, that 1) what you might have wanted to do that day anyway, 2) a service to society and 3) is going to get you a job down the road where you can get paid to do it, so add it to your CV. NSF is huge right now on "Greater Impacts", my fellowship is first and foremost to teach me and the other fellows how to communicate science to citizens, that's going to propagate down into agencies and was already there in some of academia, whatever path you end up on.

You're on a noble path. Don't let this guy ruin your day

Todd