Myth Or Not?

[Truck]

well i have allways beliveid that this is true after reading an article, which states:

" as a fish starts to become a bit big for its home, there is a hormone produced which stops the fish's body growing but not the internal organs.

But in my opinion, why would you keep an oscar in a 30 gallon? when you know it wont be happy, in my honest opinion its an accident waiting to happen. their big mesy fish

 

[Colin_T]

When fish are young they produce a hormone to stop other fish growing around them. However they stop producing that when they are mature.
It would be unlikely that they could produce a hormone that stopped the body from growing but allowed the organs to continue. If the hormone was in the water it would affect the entire fish, inside and out, organs and muscle tissue.

 

[Truck]

i thought it would have been a bodily hormone

 

[andywg]

well i have allways beliveid that this is true after reading an article, which states:

" as a fish starts to become a bit big for its home, there is a hormone produced which stops the fish's body growing but not the internal organs.

But who wrote the article and what was their background, experience and evidence?

As a rebuttal, (previously found by Bignose) in Development and aging of the liver and pancreas in the domestic carp, Cyprinus carpio: From embryogenesis to 15-year-old fish" by Fishelson L and Becker K in ENVIRONMENTAL BIOLOGY OF FISHES Vol 61 Issume (1) pages 85-97, 2001 it was noted that:

"In 15-year-old experimentally stunted fish (110-120 mm TL) the liver and pancreas resemble those of juvenile fish appearing much healthier than those of 8-10 year old large carp from commercial ponds."

Rather than the internal organs being overgrown and misshapen it would appear they were healthier than those of younger fish allowed to reach a natural size. One caveat is that Fishbase gives a max SL size of 120cm for these fish, so they have been stunted by around 10% at most as far as I can see.

There is plenty of research (mostly on farmed fish for fishing or the food market) on how less than optimal conditions causes a reduction in growth rate which will often never be caught up. I don't recall reading this will definitely lead to a shorter life.

With regards to the effects of stunting, well it will depend on what causes it. It is believed that (at least) some fish have the stunting system as an evolutionary aid for when they find themselves in small bodies of water with lower amounts of food they don't grow too large too quick. Exactly how they do this is not entirely known and there have been a number of discussions towards a hormone or chemical of some kind given off by the fish.

One thing that goes against chemicals would be that with regular water changes we would water down anything of this nature and reduce its effect. Further, in a medium sized body of water it would take a lot to notice (but then a closed system (no water changes) found equal growth rate in fish over a year and in that time one would expect the chemical/hormone to build up even in the professional sized quarters_. Perhaps, therefore, any hormones are delivered internally. No one really seems to know for sure at this point.


For those with a short attention span:

tl;dr: there appears to be some support for a growth inhibiting chemical within fish but if it exists it restricts all growth, not everything but the organs and stunting may not be the most horrendous thing you can do for a fish.

 

[joshrm115]

I'm in college right now I got to UCSD and I study chem and physics and one thing we learned was with the common gold fish '' put in a small tank the fish will only grow a few inches,but if put in a big tank this fish can grow to be over ten times the average size'' they say Oscars get up to 12 inches, but there have been records of Oscars that where only 6inches and some that where 28 inches. All animals can adapted its easier for some then others but it is a proven fact that fish grow to the tank. I would however say you will at least need a 55 gallon tank for a Oscars but it would probably be ok in a 30g I have seen them in smaller....

 

[JustKia]

"In 15-year-old experimentally stunted fish (110-120 mm TL) the liver and pancreas resemble those of juvenile fish appearing much healthier than those of 8-10 year old large carp from commercial ponds."

Rather than the internal organs being overgrown and misshapen it would appear they were healthier than those of younger fish allowed to reach a natural size. One caveat is that Fishbase gives a max SL size of 120cm for these fish, so they have been stunted by around 10% at most as far as I can see.

Forgive me if I'm wrong but if a fish has a likely (normal) max size of 120cm and has been stunted to 120mm then it hasn't been stunted by 10%, rather it has been stunted to 10%

And I would then have to ask, if this is the case how come there are many instances of fish outgrowing the tanks they are put into - surely on this basis we could all go and stick a young pacu or redtail catfish into our 2ft aquarium and it's growth would be stunted and thus not out grow the aquarium?

 

[AdAndrews]

not a myth at all, the fish you keep will grow to the size of the tank, if goldfish can get to 30cm in a tank, then how can they grow that big in say a 10 cm tank, just an example, keeping fish in smaller tanks will sometimes kill or weeken them from their insides being messed about, however if you be sensible witht this rule and not put a goldfish in a 10cm tank then it will generally work, this is why i have rainbows in my 54 litre, i see no problem with it, it isnt cruel. well until they start to die it isnt!

NOT A MYTH

 

[andywg]

Forgive me if I'm wrong but if a fish has a likely (normal) max size of 120cm and has been stunted to 120mm then it hasn't been stunted by 10%, rather it has been stunted to 10%

Indeed it has. My mistake on the units (that's what I get for posting so late, I guess). I did think at the time that the difference seemed strange. In fact it will be slightly smaller as as the 120mm is Total length (including the caudal or tail fin) whereas the 120cm is total length. One should be careful, however, on using max size as this is the largest recorded and most fish would never get to this size.

And I would then have to ask, if this is the case how come there are many instances of fish outgrowing the tanks they are put into - surely on this basis we could all go and stick a young pacu or redtail catfish into our 2ft aquarium and it's growth would be stunted and thus not out grow the aquarium?

Because these fish probably cannot stunt themselves to the level that the fish above did. Some fish may be able to curtail growth better than others. RTC live in competitive environment with many predators of smaller fish. Their survival trait is to have a huge growth rate up to around 2-3 feet from where they tend to slow down as by this point there are far fewer predators of them and they can eat far more of what is around them.

While fish can be stunted, many fish will still reach large sizes, the RTC is a good example of this.

 

[shroob]

I'm in college right now I got to UCSD and I study chem and physics and one thing we learned was with the common gold fish '' put in a small tank the fish will only grow a few inches,but if put in a big tank this fish can grow to be over ten times the average size'' they say Oscars get up to 12 inches, but there have been records of Oscars that where only 6inches and some that where 28 inches. All animals can adapted its easier for some then others but it is a proven fact that fish grow to the tank. I would however say you will at least need a 55 gallon tank for a Oscars but it would probably be ok in a 30g I have seen them in smaller....

Where can I see the records for this 28" oscar 30 Gallons isn't big enough for an oscar by any stretch.

Re internal organs. Seems I was wrong, you learn something new on this site everyday

 

[raptorrex]

not a myth at all, the fish you keep will grow to the size of the tank, if goldfish can get to 30cm in a tank, then how can they grow that big in say a 10 cm tank, just an example, keeping fish in smaller tanks will sometimes kill or weeken them from their insides being messed about, however if you be sensible witht this rule and not put a goldfish in a 10cm tank then it will generally work, this is why i have rainbows in my 54 litre, i see no problem with it, it isnt cruel. well until they start to die it isnt!

NOT A MYTH

presumably them someone with a marine tank can get a baby great white shark, put it in a 6 foot tank and it will not out grow it? or from tropical fish, a Redtailed cat fish would only grow a few inches if it were kept in a 10g tank? carp/goldfish, do exhibit the ability to adjust growth according to their environment. but it is not a trait shared by all fish, and even of those who do, many don't seem to have it to the same extent.

do fish grow to the size of the tank they are in? without doubt, NO. do fish have the ability to control growth, according to environment and food, YES. all animals do, some more than others.

 

[petertr]

yes nice info there colin t but remember a lot of the time tank sizes are given not because the fish will grow to a large size but because the fish needs a large amount of swimming space to be happy, an unhappy fish will be stressed and disease prone and they often die prematurely as an indirect consequence of the tank.

Exactly. And it's very obvious when you think of it like this:


Would you put a baby in a cage, and leave it to grow - safe in the knowledge that it will "only grow to the size of the tank".

Even if true, its horribly cruel.

 

[prankster705]

28" oscar... now that's just ridiculous... photo please

 

[OohFeeshy]

not a myth at all, the fish you keep will grow to the size of the tank, if goldfish can get to 30cm in a tank, then how can they grow that big in say a 10 cm tank, just an example, keeping fish in smaller tanks will sometimes kill or weeken them from their insides being messed about, however if you be sensible witht this rule and not put a goldfish in a 10cm tank then it will generally work, this is why i have rainbows in my 54 litre, i see no problem with it, it isnt cruel. well until they start to die it isnt!

NOT A MYTH

Urm, you appear to have missed an important point that is, generally speaking, the crux of the entire debate. Coming up with a somewhat more realistic example, let's assume you have a 1" common goldfish, and it's genetically identical twin. One goes in a 6'x2'x2', the other in a 12"x8"x8". Obviously, the former will have plenty of space for it's entire life, so will grow to full potential, healthy yadda yadda. The other one, however, will not think 'hrm, I'm currently at the optimum size for this tank in regards to swimming room, so this size will do me nicely'. While it won't grow to the same size as the one in the larger tank, it will grow to 3/4" or so. Which gives it nowhere near enough space to move properly.

For instance,
http/www.bodiless.org/pets/Goldfish-Tank.jpg
According to the website, these fish are feeder goldfish that have always lived in a 29g. Seems like plenty of room, but looking at the picture, can you honestly say they have enough space? Not really. The same story is true for practically every tank of this sort of situation.

 

[Jazzzz]

how about someone does an experiment with the fish kilss them humanly and measures organ size etc

 

[raptorrex]

how about someone does an experiment with the fish kilss them humanly and measures organ size etc

how about we just keep the fish in an, appropriate size tank? must be simpler and better for the fish.