Dwarf pangasius sharks!?

[Moontanman]

I am currently planning a large tank (750 gallons or so) and I plan to put lots of small fish like Cardinals in it as well as lots of non aggressive catfish.

There in lies the crux of my issue, like most people when I begin to set up an aquarium I do as much research as possible by scanning online fish "porn" you dudes and dudettes know what I mean and I do have some great catfish picked out. I intent for most of the fish to be catfish by species number if not by individual numbers.

On to the chase, about 20 years ago I had a Pangasius shark that never grew more than some place around 10" or so. A pet shop owner gave him to me, he had obtained him in a trade with the person who raised him in a 20l. He was the calmest Pangasius shark i had ever seen, no scars or missing eyes like they usually get from running around in a tank and baging into the decor. He would eat from my hand and allow me to touch him. He was a great fish! Despite living in an outdoor pond in the summer, we have very long hot summers here and i can often keep fish in outdoor ponds for 8 months out of the year. When I got him he was the same length, 10", and over five years he never grew at all. He was a great feeder and ate almost anything. He seemed particularly fond of daphnia magna that i culture.

He was the perfect aquarium fish, I kept him and his tankmates in a 125 during the winter and he lived with fish as small as cardinal tetras and never seemed to even notice them. The only problem was he didn't get along with the elephant nose fish very well.

The question is that I am starting to see ads for dwarf Pangasius sharks, they look the same as the regular ones and the one I had as well. Is someone breeding dwarf pangasius sharks? Is it possible i had one of the dwarf ones?

Thoughts?

[Jools]

I've seen balloon forms, which might be what they are. Or they could just be regular ones being mis-sold.

Jools

[Moontanman]

I've seen balloon forms, which might be what they are. Or they could just be regular ones being mis-sold.

Jools

They weren't the balloon ones for sure, I know the one I had wasn't, I would still have him if not for a heron I hates me some heron

[Viktor Jarikov]

My experience and my take on this is that there appears to be two large groups of IDS in the trade, ones that grow big and quick (~1.5' in the first year, 2'+ in 2 years) and ones that grow slow and to a small size, usually 8"-10". These I think are the dinks and runts, just as your paddlefish were, Michael, culled from the fish farms that produce tonnes of IDS for food.

This may elaborate more http://www.monsterfishkeepers.com/forum ... es.505668/

[Moontanman]

My experience and my take on this is that there appears to be two large groups of IDS in the trade, ones that grow big and quick (~1.5' in the first year, 2'+ in 2 years) and ones that grow slow and to a small size, usually 8"-10". These I think are the dinks and runts, just as your paddlefish were, Michael, culled from the fish farms that produce tonnes of IDS for food.

This may elaborate more http://www.monsterfishkeepers.com/forum ... es.505668/

You could very well be correct, my experience and some other anecdotal evidence points to the possibility of "dinks". Here is the thread I posted in MFK, it was an old thread but maybe it will stir up some responses.

I know this resurrecting a dead thread but I would like to discuss this idea of stunted vs possible species.

I to have kept a pangasius shark that stayed small no matter what i did. A pet shop owner gave him to me when the fish was about 10 to 11 inches long. Supposedly he had been kept in a ten gallon tank for several years and had outgrown it. I took him home and after a few days of quarantine I put him in my 125. He ate like a pig, didn't bother even small fish like cardinals.

He drew the wrath of an elephant nose fish for some reason and it harassed him incessantly , seeming to give him a slight electric shock when they encountered each other.

I had the pangasius shark for several years, he never grew perceptively and stayed around 11" long.

I live where I can put my fish outside for 8 months a year in my yard pond so the pangasius got to vacation every summer in a several hundred gallon yard pond. He was easy to catch, wasn't nervous or skittish like most pangasius sharks are. In fact he would take food from my hand.

Most of the time i fed the fish in the 125 daphnia that I raise, trout worms, opened clams and Hikari pellets, the micro pellets if I remember correctly.

He spent at least three summers in the pond but one day I came home from work to hear my neighbor tell me how a huge bird was in my pond, she thought it was beautiful but that bird/Heron pretty much cleaned out my pond including the pangasius shark.

I tried to compare him to other pangasius sharks in the pet shop hoping to find one just like the one that became bird food but I couldn't find one that was any different than the rest of them...

I have honestly given some thought to seeing if I could reproduce the stunting, maybe buy 12 and put them in a 40 breeder tank and see if any of them stop growing at around 10" or so.

The one I had made a striking display swimming around among tetras and other small fish. The only other fish close to his size was an elephant nose fish and three 12" hog chokers i raised from larvae.

[Viktor Jarikov]

I doubt you'd find anybody, at least on here or MFK, who would support or at least be indifferent to an intentional stunting of a fish. Many people do it unintentionally left and right and then get unpleasant comments for it. Intentionally doing so is considered probably by most or all an animal cruelty.

One advice I can give is that when you go to an LFS and see a bunch of IDS, pick the smallest. In general, they come in at 2"-3". If you see a 4"-5" and larger IDS, that's likely a normal one that should grow quick and big.

Sometimes, I keep visiting the same LFS and seeing the same IDS group for weeks or months, when the sales are slow. At the end of this period it may become clear which ones have a higher chance to stay smaller and which ones do not.

[Moontanman]

I doubt you'd find anybody, at least on here or MFK, who would support or at least be indifferent to an intentional stunting of a fish. Many people do it unintentionally left and right and then get unpleasant comments for it. Intentionally doing so is considered probably by most or all an animal cruelty.

One advice I can give is that when you go to an LFS and see a bunch of IDS, pick the smallest. In general, they come in at 2"-3". If you see a 4"-5" and larger IDS, that's likely a normal one that should grow quick and big.

Sometimes, I keep visiting the same LFS and seeing the same IDS group for weeks or months, when the sales are slow. At the end of this period it may become clear which ones have a higher chance to stay smaller and which ones do not.

I understand what you mean, it was just a thought, I have much more pressing things to spend my money on than 12 IDS just see how fast they grow.

But the mechanism for the small size might be something other than environmental. The one I had most certainly wasn't stunted by me, he was one of my favs and got the best of everything including consistently changing water. I let my well water run into the tank all the time and it exited by an overflow into the sewer in my garage. I have been told many times the fish would have continued it's growth if i had treated it right... I am sure we all know people who think they know everything about keeping fish and love to criticize others. I don't do many forums due to the trolls but I do wonder about the mechanism behind some fish growing large and others not.

I do not agree that a stunted fish is somehow being abused and fisheries scientists agree with me. In fact we are causing wild fish populations to down size via the methods we use to decide which fish to keep and which ones to release.

I live in the southern USA and fish that northerners expect to be big simply do not get that big here. A case in point is yellow perch. Up north they catch really big ones, here they breed at around 4 or 5 inches and I have never seen one more than 7 or 8 inches long. I do know people who claim to have caught 12" yellow perch but it the exception rather than the rule.

I participate in population studies of native fish, we get to seine and use electro shockers, we often catch some odd stuff! A good friend of mine literally wrote the book on native fish of this region. Things get strange in some areas where fish are not what they are in other places. I blame epigenetics, I can catch a siren 4 feet long and big around as my upper arm but bullfrogs seem stunted compared to the ones i used to catch in the mountains.

Large mouth bass get huge as do some sunfish but others do not grow big enough to even catch. I would love to know the how and why of the stunted fish, actually I don't think it's fair to call them stunted, some might be, but some seem to be something else and i would love to know the what and why.

I've caught some bowfin that would make you think twice about going swimming... lol

I've been keeping fish for 50 years, I still learn something new on a regular basis...

[Viktor Jarikov]

You likely know lots more on stunting than I do, but just in case I've put together several good links on stunting, about mid-page here Thu Mar 20, 2014 10:07 pm (I wish our posts had #s, it'd be much easier to point) http://www.planetcatfish.com/forum/view ... ilit=thumb

IDK if selectively disposing of underperformers (releasing them back in the wild or redirecting them into the ornamental fish trade) would fall under a stunting definition. It may. I am just ignorant. When I think of stunting, the first thing that comes to mind are the studies on growth hormones released by fishes into their water, which, ironically, that is, as opposed to growth, actually inhibit the growth of their own and their tank mates.

Too small quarters would not only exacerbate the hormone effect but also would lead to other things like the brown blood disease which causes internal organ damage long-term, so such fish are unlikely to reach their potential. People tend to think, it appears, it is that the fish has not much room to swim, which is a factor, but primarily, I'd think it is biochemical - hormones and toxins poisoning them.

From my patchy understanding, the tank+sump volume should hold enough water to instantly dilute ammonia and nitrite to safe levels before it is taken care of by the filter bacteria. When this does not happen, perpetual low-intensity but long term exposure to ammonia and nitrite will wear fish out. Especially nitrite, because it robs blood cells and fish have no bone marrow to quickly replace them.

[Moontanman]

I know little to nothing about why fish don't grow to their potential, I do know that expecting a fish to grow to it's maximum recorded adult size is unrealistic. I'm not sure how big we should expect a fish to get, the variability is difficult to pin down.


I have been considering the possibility that stunting happens when the fish is very small or that some of the fish are indeed "dinks" Maybe I'll find another IDS or two that have been taken back to the pet store after they out grow their 10 gallon aquarium!

The possibility that the small size is not stunting but a natural occurrence when fish over populate their environment. I know it happens in the wild, occasionally a pond or small lake with become populated with huge numbers of normally large fish but the lake will contain no large individuals.

Epigenes could be the controlling factor or it could be the species is more variable than we think or a hidden new species that mimics the IDS but doesn't get as big. I am doing a study right now on a suspected "shadow" species but that will take several more months to even show proof of concept...

[Viktor Jarikov]

MM: I know little to nothing about why fish don't grow to their potential, I do know that expecting a fish to grow to it's maximum recorded adult size is unrealistic.
VJ: I'd agree but in practice the main reason appears to be that we are not able to keep a large-growing fish successfully for the times needed for them to reach the max size or the vicinity thereof. Take RTC for instance. If we kept them for 25-50+ years, they might have grown to 5'+. Vast majority of them that make it into adulthood die early - 5-10 years old - and relatively small - 2.5'-3.5'. I only know of one that hit 4', that Arapaimag aka Michael Bryce reported that lived in his 52,000 gal tank. Taksan had a pair for 27 years in 15,000 gal pond, they died not reaching 4' but this does not mean others could not. Too few occurrences.

MM: I'm not sure how big we should expect a fish to get, the variability is difficult to pin down.
VJ: For some fish we know better, for some / most we know worse but I'd agree that being sure is out of the question most usually.

...

MM: The possibility that the small size is not stunting but a natural occurrence when fish over populate their environment. I know it happens in the wild, occasionally a pond or small lake with become populated with huge numbers of normally large fish but the lake will contain no large individuals.
VJ: I've read such articles too. I think it is precisely stunting via hormones in their water as well as undernourishment. Are you counterposing stunting and natural? I mean is stunting always something artificial?

MM: Epigenes could be the controlling factor or it could be the species is more variable than we think or a hidden new species that mimics the IDS but doesn't get as big. I am doing a study right now on a suspected "shadow" species but that will take several more months to even show proof of concept...
VJ: This is way above my head I had to look this up - http://www.whatisepigenetics.com/what-is-epigenetics/ :

In simplified terms, epigenetics is the study of biological mechanisms that will switch genes on and off. What does that mean? Well, if you are new to this whole thing, we first need a quick crash course in biochemistry and genetics:

Cells are fundamental working units of every human being. All the instructions required to direct their activities are contained within the chemical deoxyribonucleic acid, also known as DNA.

DNA from humans is made up of approximately 3 billion nucleotide bases. There are four fundamental types of bases that comprise DNA – adenine, cytosine, guanine, and thymine, commonly abbreviated as A, C, G, and T, respectively.

The sequence, or the order, of the bases is what determines our life instructions. Interestingly enough, our DNA sequence is mostly similar to that of a chimpanzee. Only a fraction of distinctively different sequences makes us human.

Within the 3 billion bases, there are about 20,000+ genes. Genes are specific sequences of bases that provide instructions on how to make important proteins – complex molecules that trigger various biological actions to carry out life functions.


Now that you understand genetics, let’s learn about epigenetics. Epigenetics, essentially, affects how genes are read by cells, and subsequently how they produce proteins. Here are a few important points about epigenetics:

Epigenetics Controls Genes. Certain circumstances in life can cause genes to be silenced or expressed over time. In other words, they can be turned off (becoming dormant) or turned on (becoming active).

Epigenetics Is Everywhere. What you eat, where you live, who you interact with, when you sleep, how you exercise, even aging – all of these can eventually cause chemical modifications around the genes that will turn those genes on or off over time. Additionally, in certain diseases such as cancer or Alzheimer’s, various genes will be switched into the opposite state, away from the normal/healthy state.

Epigenetics Makes Us Unique. Even though we are all human, why do some of us have blonde hair or darker skin? Why do some of us hate the taste of mushrooms or eggplants? Why are some of us more sociable than others? The different combinations of genes that are turned on or off are what makes each one of us unique. Furthermore, these epigenetic changes can be inherited.

Epigenetics Is Reversible. With 20,000+ genes, what will be the result of the different combinations of genes being turned on or off? The possible permutations are enormous! But if we could map every single cause and effect of the different combinations, and if we could reverse the gene’s state to keep the good while eliminating the bad… then we could theoretically cure cancer, slow aging, stop obesity, and so much more.


Here’s an analogy that might further help you to understand epigenetics. Think of the human life span as a very long movie. The cells would be the actors and actresses, essential units that make up the movie. DNA, in turn, would be the script — instructions for all the participants of the movie to perform their roles. Subsequently, the DNA sequence would be the words on the script, and certain blocks of these words that instruct key actions or events to take place would be the genes. The concept of genetics would be like screenwriting. Follow the analogy so far? Good. The concept of epigenetics, then, would be like directing. The script can be the same, but the director can choose to eliminate certain scenes or dialogue, altering the movie for better or worse. After all, Steven Spielberg’s finished product would be drastically different than Woody Allen’s for the same movie script, wouldn’t it?

[Moontanman]

Epigenes can do some odd things like make your grandchildren more susceptible to obesity if you grow up with less food than you need... or something like that!

It would be interesting to see the process of breeding these fish and compare captive bred with wild populations. I would like to see what they do with dinks or even if that is a thing with IDS. One more thing, if you could get some actual dinks would they breed true? I had that thought with my paddlefish but life events prevented that from happening...

I know the dinks thing actually happens with some fish, I visited a trout hatchery and they had dinks in a large aquarium in the lobby. They told me the dinks were several years old and it happened at a rate that could be predicted.