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So, supposidly fish stunting comes from high nitrate levels. Well, other than high nitrate levels, and a tank that the fish will not be able to fit into, is there anything else that causes stunting?

Heated water and not enough food to balance out the faster growth........Poor water quality in general......
Improper diet can cause deformities........Overstocking can also stunt growth but thats kinda the same as tank size as your just not giving them enough room..........

Overstocking can also stunt growth but thats kinda the same as tank size as your just not giving them enough room..........

Overstocking can have a dual impact - many juvenile fish secrete growth-inhibiting (probably, but not necessarily, species-specific) hormones so as to glean an advantage over their brethren; in overcrowded conditions, or without frequent conduction of water changes for even a single captive specimen in a small setup, these compounds have the tendency to overaccumulate.

I don't feel this to be stunting in the conventional sense, but would like to note that marked morphological changes may be implemented, contingent on certain environmental cues, as a means of defense:

Crucian carp from populations that lack piscivores are extremely vulnerable to
predation. However, in the presence of piscivores these fish develop an inducible
morphological defence, a deep body. This switch from a vulnerable, shallow-bodied
morph to a morphologically defended morph makes this species very suitable for
investigations of anti-predator strategies, and trade-offs between morphological and
behavioural defences. To address these questions, we performed eight different
experiments. We found that crucian carp exhibited fright responses to chemical cues
from unfamiliar predators (northern pike, perch) when these were fed prey that
contained alarm substance (for northern pike: crucian carp, roach; for perch: crucian
carp). Cues from small pike that were fed prey that lacked alarm substance
(swordtails) caused no significant fright response whereas cues from larger pike with
the same diet did. Perch on a chironomid diet elicited weaker but significant fright
responses. Starved predators caused as strong fright reactions as recently fed ones
did, whereas no response was exhibited towards nonpredatory fish (roach, crucian
carp). Crucian carp were able to detect the presence of pike after cues had been
diluted to an equivalent of 21000 l, and larger predators elicited stronger fright
responses. Prior experience of predators decreased fright responses. In particular,
individuals from populations that coexisted with northern pike responded less to
chemical cues from northern pike than individuals without prior experience did.
Thus, crucian carp may use both alarm-substance related and predator-related cues
to identify predators. Further, they were able to discriminate between large and small
predators. Finally, individuals from populations that coexist with predators exhibit
less ounced fright responses. These fish have an induced morphological defence,
a deep body, which most likely decreases the need for strong antipredator behaviour.

From http://www.limnol.lu.se/limnologen/publikationer/159.pdf.



Last edited by Veneer at 24-Mar-2005 09:12

Tilapia are sexually mature at three years of age or less in favourable conditions. They are able to reach sexual maturity at small sizes in poor conditions or when they are overcrowded. This is known as 'stunting' and results in large populations of mature fish with small body sizes.

From http://www.dpi.qld.gov.au/fishweb/1406.html.

Therefore, in less-than-optimal conditions, the growth rate of tilapia (here, Oreochromis and Sarotherodon spp.) grinds to a standstill, yet population recruitment does not cease; thus, conspecific competition (for such resources as food) escalates exponentially with each new generation, and the stunting trend reinforces itself with a chain of, as it were, positive ("negative" from the perspective of the mariculturist) feedback.

While some sources state [as follows] that adult fish either "self-prescribe" or continuously release growth-inhibiting substances, others are inclined to dispute the validity of such a far-reaching claim.

The myth of the shrinking fish is based on the convoluted fact that fish are able to self induce growth stunting via a self prescribed growth stunting enzyme.
The triggers to release this substance are (i) exposure to poor water quality and (ii) over population (a condition which is replicated in small aquaria).

From http://www.perthaquarium.com.au/feature3.htm.

Look to "Growth-Inhibiting Substances of Fishes" for further insight.

Last edited by Veneer at 24-Mar-2005 09:41

UVB Radiation:

The proliferation of ozone-eating chemicals called chlorofluorocarbons (CFCs) has led to the thinning of the ozone layer above Britain by 10 per cent in Spring when fish spawn and when they are most vulnerable to the most damaging rays, known as UVBs. These rays blister the skin of young fish and cause it to thicken, slowing their oxygen intake, stunting their growth and leaving them more vulnerable to predators. The UVB rays also react with pollutants in the water to produce toxins up to 10,000 times more potent than normal.

From http://www.truehealth.org/climnw06.html.

A dissenting opinion:

Causes of "stunting" fish populations

"Stunting" is typically assumed to a result of overcrowding and intensified competition for limited food resources. However, available evidence does not support this supposition. I am exploring the possibility that stunting is instead an adaptive life history response to environmental conditions favoring high survival and growth rates of early history stages.

From http://www.bemidjistate.edu/dsiems/research.htm.

It's somewhat difficult to generalize across the full breadth of fish, so, while this premise may hold under certain circumstances, it is, in all probability, not necessarily exclusively complicit in all instances of "stunting".

According to http://www.drsfostersmith.com/pic/article.cfm?dept_id=0&aid=127:

Niacin (Nicotinic Acid): Aids greatly in growth. Lack of this vitamin causes stunting.

I don't know whether this conclusion was based on empirical experimentation with fish or was simply extrapolated from human physiological response.