What Causes Stunting?

[rdd1952]

In looking around for information on stunting (another topic that comes up a lot), I found this and this artcile. I don't know whether I believe it or not but it would seem to make sense. I have always heard it said that the fish's body stops growing but the organs don't leading to an early death but have also seen statements that this is just a myth. Does anyone else have references on what actually causes stunting?

 

[andywg]

I seem to recall that as fish grow they release some hormones into the area around them. An accumulation of these hormones induces less growth, but can't think where I read it. This would explain why people who do regular water changes have their oscar outgrow their 10 gallon so quick, yet that fairground goldfish with no water changes stays small for so long.

The organs thing is almost certainly a myth. There would be no benefit to a skeleton staying small when the organs don't. What evolutionary purpose would it serve? I think the thing to do here is to request evidence of oversized organs in a stunted fish.

Beamish and Tandler (1990) noted that an un-ionized ammonia concentration of 198 micrograms per litre affected food uptake and growth of juvenile lake trout (Salvelinus namaycush). It further appears that Brett (1979) covers the effects of environmental factors on growth as presented by Fry (1971).

The papers above in the order mentioned are

Ambient ammonia, diet and growth in lake trout. Aquatic Toxicology 17:155-166

Environmental factors and growth Fish Physiology Vol. VIII, Bioenergetics and growth p. 599-675

The effect of environmental factors on the physiology of fish Fish Physiology Vol. VI p. 1-98

 

[rdd1952]

I seem to recall that as fish grow they release some hormones into the area around them. An accumulation of these hormones induces less growth, but can't think where I read it. This would explain why people who do regular water changes have their oscar outgrow their 10 gallon so quick, yet that fairground goldfish with no water changes stays small for so long.

So, do you think it would be a combination of the hormones in the water and poor water conditions in general or simply the growth hormones. I will have to try to find the books you mentioned but doubt I can find them online. A trip to the library would be in order. I would assume that overstocking could also result in stunting but that could be an indirect result going back to poor water conditions, excess hormones or competition for food.

 

[jayjay]

An interesting thread on stunting with some fairly good evidence provided by nmonks, here.

 

[andywg]

There is a lot of research into the growth of fish, it is just a matter of finding those that most apply. It would seem that growth is more likely to be controlled by chemicals than by the physical environment as a volume. Biology of Fishes by Bond notes that fish can grow in a serious of sigmoid curves to represent different stanzas of the creature's life (such as temperate fish not growing in winter, but then growing swiftly in summer).

 

[ArauraDiscus]

I agree with andy on the hormone accumulation and water changes or lack thereof. My grandmother had a 10 gallon tank that almost never had it's water changed. She had a common pleco and an angelfish. The angelfish died of ich and she gave me the pleco. The pleco was 5 inches then, and now 2 years later it is still 5 inches. The lack of water changes could theoretically lead to the accumulation of the hormones and the stunting of my pleco. It looks like he will remain this size forever now.

 

[Aphotic Phoenix]

I would suggest that in addition to hormones there could also be factors involving the "reassignment" of bodily energies towards maintaining a stable body system in an inadequate environment. For example, energy expended towards osmotic-regulation instead of bodily growth. Also, depending on the severity of conditions decreased enzymatic function on a cellular level could limit the uptake of nutrients, or the creation of new bodily proteins regardless of diet. This could explain why certain species of fish will once again increase in body size after being placed in a new environment, while others (like ArauraDiscus pleco) do not.

Please note that I'm just creating hypothesis out of my somewhat limited biological background.

 

[andywg]

I would suggest that in addition to hormones there could also be factors involving the "reassignment" of bodily energies towards maintaining a stable body system in an inadequate environment. For example, energy expended towards osmotic-regulation instead of bodily growth. Also, depending on the severity of conditions decreased enzymatic function on a cellular level could limit the uptake of nutrients, or the creation of new bodily proteins regardless of diet. This could explain why certain species of fish will once again increase in body size after being placed in a new environment, while others (like ArauraDiscus pleco) do not.

Please note that I'm just creating hypothesis out of my somewhat limited biological background.

osmoregulation can indeed play a part.

Kinne (in 1960) noted that the euryhaline desert pupfish grew faster at 35ppt salinity than more or less saline waters.

Brett (1979) noted that growth will decrease in response to increased maintenance energy requirements (due to sub-optimal conditions) where ingested food energy and energy excreted remain constant.

 

[rdd1952]

(such as temperate fish not growing in winter, but then growing swiftly in summer).

If he is speaking of fish in the wild which I assume he is since fish in our tanks don't experience seasons (or do they?), I would think that could be partly due to food availability. In the winter, with insects killed off by the colder weather, food would be in short supply. In the spring though with insects starting to come out and fish spawning (fry to eat) food would become plentyful again resulting in a growth spurt.

Also an interesting thread and posts from nmonks and Fella.

 

[andywg]

Not just the wild, per se. Most of the research is done for fisheries which could easily provide food in winter, but the slower metabolism will slow growth.

the point I am making is that growth is not linear. Fish can spurt in size once they have better conditions. I am fairly sure that CFC had a lot of fish in his 200 gallon before his move that had seemed to almost top out. Once he moved and split them across more tanks a number started to grow quite rapidly.

I would wager that a 10 gallon tank on a constant water change (say 50-100% per day) would allow an oscar to grow pretty large at the same rate as one in a 100 gallon tank with regular water changes (providing food and temperature and other variables are kept constant).

 

[Gremily]

I would wager that a 10 gallon tank on a constant water change (say 50-100% per day) would allow an oscar to grow pretty large at the same rate as one in a 100 gallon tank with regular water changes (providing food and temperature and other variables are kept constant).

This is quite interesting, so do you think artificially adding this hormone to a large capacity tank would cause a fish to be stunted as it would be in a small tank? Is it exclusively the hormone that causes stunting?

 

[OohFeeshy]

It's very hard to say. I haven't had a look at the papers posted earlier yet, but almost all papers on the subject refer to farmed fish like salmon. And I'd be willing to bet that you'd have a hard time isolating or even producing such hormones, let alone working out which does what and in what concentrations you need.

The problem with questions like this is the ethical side- while an easy solution (to at least parts of the problem) would be for somebody to buy several common goldfish and keep them in varied conditions (frequent water changes, chemical ammonia removal, multiple fish, diet, etc), there would almost certainly be backlash from others.

 

[Tokis-Phoenix]

I read an article ages ago (can't seem to find it at the moment), where they said that apparently nitrites can cause stunted growth in certain varieties of fish such as goldfish for example.
They were saying that the reason why poor water quality conditions cause stunted growth in some types of fish was because in the wild, such bad water quality conditions often indicate something else like a drought drying up the lake, and in such times it would be a bad idea for the fish to grow. So over time, some fish have evolved to have stunted growth when conditions in their habitat are not ideal- the problem with this in aquariums is that these conditions often last for ages and never get better like they might in the wild because the owner thinks that their goldfish bowl is fine for their goldfish to live permanently in etc, and this takes a toll on the fishes life expectancy in the long term etc.



Ultimately though, generally speaking, i have noticed that most people who put fish in tanks far too small for the fish tend to neglect a lot of other area's as far as caring for the fish is concerned, like a good varied diet feed on an appropriate/regular basis, and clean water quality conditions and appropriate habitat etc. I think all these factors probably contribute to poor growth/development in the fish one way or another, not just the lack of space.

 

[andywg]

I read an article ages ago (can't seem to find it at the moment), where they said that apparently nitrites can cause stunted growth in certain varieties of fish such as goldfish for example.

That would tie in with one of the papers mentioned in my first post, about quite small levels of ammonia affecting growth.

 

[jollysue]

Would the ability to get the appropriate excercise also affect the fishes growth?

I experienced the growth spurt, when I moved my blue Moba frontosa to the larger tank. The Bismarks stayed behind and have not had the same growth spurt. But the water quality in both tanks would be similar. I was doing lots of water and filter maintence changes (weekly and by weekly) before the change. Same now, the water quality is similar. I did no controlled studies. lol

I seem to remember that the hormone thing had not been applied to all fish as yet. Well last time I read on it. It also is a more recent area of research, I thought, so some things that were accepted explanations or theories could be outdated.