The adaptable fish myth?

[nerdyguy83]

All of these examples still go back to the point that we are talking about fish that have been in their environments for generations or, in the case of the ponds above, fish that were probably selected for size for each pond. None of this proves that if you take a fry from the wild or captivity that has parents that grew to 10" and put it in a 10 gallon tank, the fry would only grow to 4" or whatever would be healthy for that volume of water.

 

[Rowangel]

Are they stunted or otherwise not living a fulfilled life because they are in a small creek? I think not. they just grew to what there environment (size, food availability, etc) would allow.

Is it that the fish are growing to their environment or is it that the environment can’t sustain fish over a certain size? Big fish may not be able to out compete smaller, faster fish that require less food. There are far too many variables in nature to account for differences in size from location to location. It would be hard to prove with any accuracy one way or another if the fish are adapting or if something else is occurring.

I think it is hard to get past the point that adaptation, for whatever reason, occurs over time-not over one fishes life. An Oscar cannot be expected to stay small with less food and a smaller tank because it’s genetic make-up has been programmed to grow to a predetermined size. Any evidence of reduced size is due to an interruption of this natural growth. Better environment = faster, stronger growth, bad environment= slower, weaker growth, but it will still grow regardless. If this means stunted growth that effect the internal organs then death may interrupt this process before the fish reaches it's final size. Possibly another reason why you find smaller trout? *shrug*

 

[stingray4540]

All of these examples still go back to the point that we are talking about fish that have been in their environments for generations or, in the case of the ponds above, fish that were probably selected for size for each pond. None of this proves that if you take a fry from the wild or captivity that has parents that grew to 10" and put it in a 10 gallon tank, the fry would only grow to 4" or whatever would be healthy for that volume of water.

Not exactly. for my example of the trout, they are planters from the same hatchary, this isn't like comparing native fish that have been there for centuries. these are all the same generation.

Also, the pond example, I used to have a pond as well as all my neighbors and friends. I used to even help manage a few. Most ponds were stocked by the same hatchary. Most of the ponds were roughly the same size so I can't vouch for the other pond example, but I did notice that the ponds that were stocked lighter produced bigger fish. the heavier stocked ponds produced smaller fish, but better catch rate.
Obviously, these examples pertain to the size reached after adult size. for example, I would concider an adult trout at 12in. anything bigger would be a product of it's environment.
I don't think the question is whether an oscar can be kept in a ten gallon and only grow six inches, but rather, determining the minimum adult size and accomodating them to at least that. I stress the minimum adult size, because it seems that in the aquarium trade size of a fish varies by source, as well as it seems that the average size is given and not the size at which the fish reaches maturity.

 

[Rowangel]

I don't think the question is whether an oscar can be kept in a ten gallon and only grow six inches, but rather, determining the minimum adult size and accomodating them to at least that. I stress the minimum adult size, because it seems that in the aquarium trade size of a fish varies by source, as well as it seems that the average size is given and not the size at which the fish reaches maturity.

Bingo! : Heh, heh. With more room and more food, fish will take advantage and growth will increase. One Oscar given a large environment, varied food and no competition or predators will grow fast and big, well past its 'minimum adult size.' But this, of course, dose not mean that the same fish will stop growing to fit a smaller environment, growth will continue at a slower pace, but it will continue till the small environment kills it one way or another.

 

[daveedka]

O.k. I didn't read all of the information yet, but Tried to skim for content. You'll have to kick me in the teeth if I am repaeting someone elses thoughts.

Fish grow for their entire lifespan at some rate or another. In the wild Food type, food quantity and climate are the typical controlls. For instance Bass that have shad avaialable will grow larger than Bass that only get Crayfish. As long as the population of bass is small enough to leave plenty of Shad for the whole population the fish will grow large, if food runs out fish don't grow as large. Lastly, the warmer temps found further south increase the amount of time that fish will feed heavily and grow during the course of a year. They also increase the life span f the fish in most cases because Bass prefer warmer water to a degree. Cooler temps slow metabolism, limit feeding and therefore limit growth.

So those are the three primary factors that govern wild bass growth rates. Genetics is the only remaining factor and while genetics has some bearing it is not a lot when it comes to fish.


Now in our tanks, Stunting occurs when fish are put in Extremely crowded environments, Stunting is the effect of the fish growing internally nbuit not externally. organs are compressed, bodies are deformed to some extent, and fish die young.

Next is the effect of limiting Growth via food. I have done this with Oscars, and find them to be very healthy fish just not the 14" monsters that Folks are used to. I don't overfeed, and I don't starve my fish. I feed once or twice a week with good balanced meals and throw in some small treats such as snails or guppies so they get to hunt a little bit. I don't think My Oscars ever looked bloated or overstuffed. They grow to a very healthy 9-10" in most cases and take a couple of years to get to that point. If you feed the same fish heavily each day it will hit the 12-14" mark in ayear or so.

Discus breeders feed their fry very heavily to increase adult size and they get Big ugly dinner plate sized fish when IMO, and nice healthy 6" fish with good color would have been more desireable.


So in a nutshell, You can limit growth via food type and quantity without harming a fish, You cannot limit growth via tank size without harming a fish to some extent or another.


Dave

 

[Rowangel]

So in a nutshell, You can limit growth via food type and quantity without harming a fish, You cannot limit growth via tank size without harming a fish to some extent or another.

So, in response to the original question, would you say 'No, fish do not grow to the size of their enclosures?’ But that you can, for a short while, slow the HEALTHY growth of a fish through selective feeding? I would say this makes sense.

would you consider this adaptation? Size can only be slowed-not permanently changed...so is it 'adapting' or just being slowed down by limiting factors? I would say slowed down, not adapting...

 

[nerdyguy83]

I don't think it is an adaptation. It is a forced behavior that appears to be a natural adaptation because in nature a smaller environment will almost always mean less food. If you put a sizeable number of fish into a small pond and fed them all they could eat, they would have stunted growth. It is the same as putting an oscar in a 10 gallon tank and feeding it daily.

 

[gagaliya]

some put a pacu in a 10 gallon and end this discussion already. it's been argued to death many times.

a fish will adjust to their tank size by shrinking a REASONABLE percentage of their body size (btw that's not healthy for the fish). but that does not mean you can dump a pacu or arrowanna into a 10 gallon for their entire lifespan. guess what the fish will grow to be bigger than the tank.

 

[nerdyguy83]

If you don't want to read this discussion because you've seen it before, then don't. I have personally never had this discussion, and I am enjoying it. A pacu in a 10 gallon sounds like a bad idea to me even if you only feed it once a week, so I'm not sure if that comment was supposed to be sarcastic or just designed to incite the rest of us. It was definitely in bad taste. I did say an oscar fed every day, and that would definitely be a bad idea in a 10 gallon except for the first month of its life possibly.

 

[Toirtis]

One thing not yet touched on here is water quality....keep 5 fish in a 20 gallon tank, but have a constant water-change system running, so that the volume of the tank is replaced 2-3 times daily (along with good filtration), and you will see a very significant difference in growth over an identical 5 fish kept in an identical 20 gallon, but with once weekly 50% water changes. Even changing 30% of the water ever 2nd or 3rd day will make a difference over 50% once weekly.

Fresh water goes a long way to keeping nitrates (and other pollutants) at or close to nil, and may have an additional impact if some of the theories ( that fish release minute amounts of hormones/pheremones into the surrounding water that slow growth when they reach certain concentrations) are true.