found this in my wanderings thought it might be interesting to the group


Pheromones and Fish
Low stocking densities can help minimize bacterial and viral disease
problems. It is presumed that the fewer the fish in the water the less
the concentration of pheromone present that suppress the immune system.

Although the following essay demonstrates the effect of hormones on the
immune system, other hormones can have an effect on the growth of koi.
If a koi does not grow in your collection, experiment by removing it to
another pond, if possible. If it starts to grow then you know that the
hormones from the other fish were affecting the growth of that
particular fish. If it does not grow then one of two things has happened
- the genetics of the fish has dictated the size of the fish or the fish
is older than you know or realize. Just as in all creatures, growth
hormones stop after a certain age and the creature stops growing.

A study by Perimutter, Alfred, Daniel Sarot, Man-Lin Yu, Rocco Filazzoia
and Seely on the Effects of Crowding on the Immune Response of Fish
indicates that there are 'other' hidden factors at work than first meet
the eye.

These are not readily visible or apparent to most koi keepers. Sometimes
we simply notice that our koi die without explanation. Perhaps the study
by Perimutter et al. throw some light on this phenomena. Their study
may indicate that fish kept in overcrowded conditions suffer impaired
immune systems as a result of biochemical agents released into the water
by the other fish living in the pond. This may be natures way of
reducing a large population to more acceptable levels. The studies
suggest that fish can release immune suppressing pheromones (hormones)
in overcrowded conditions. This makes the other fish in the system less
able to fight disease.

To investigate their suspicions three separate experiments were set up.
These involved different treatment and control groups.

The first two experiments had 30, 15, 5 and 5 fish respectively. Four
similar control groups were set up. Fish were assigned randomly among
the groups. All ponds were the same size.

The water in the treatment groups had methylchloroform added to remove
organic substances. The control groups were not treated but simply
monitored.

Ammonia, nitrate, dissolved oxygen, carbon dioxide and pH were monitored
regularly.

The immune systems were challenged with infectious Pancreatic necrosis
virus. All fish in the treatment and control groups were injected with
the virus two weeks after the experiment began. Two week later they were
injected again.

The researchers made antibody tests. These antibody measurements showed
that maximum antibody reaction occurred three weeks after the second
injection of the virus.

Looking through the results shows that the fish from the experimental
groups had two to four times the antibody levels than the fish from the
control groups.

As the level of crowding increased so the difference between the groups
increased. The implication was that the methylchloroform was removing
something from the water that affected the fish immune response. This
unknown factor was directly proportional to the crowding level. The
greater the crowding level the greater the immune suppressing effect.
The evidence suggested an immune suppressing pheromone was present.

To check their findings the authors then decided to refine a third
experiment. This third experiment was run twice with each of the four
treatment and control groups. These being 30, 15, 5 and 5 fish again.

The results were as follows.

1. The groups of fish at low stocking densities had twice the antibody
level of the control groups.

2. The groups with slightly higher stocking densities had four times the
antibodies present.

3. However, as the stocking densities increased the effect of the immune
suppressing agent became more pronounced. There were less and less
antibodies recorded in the test groups.

4. It is worth noting that even at low stocking densities there was a
lower antibody count. This indicates that even at low stocking densities
there is immune response suppression.

Conclusions: Low stocking densities can help minimize bacterial and
viral disease problems. It is presumed that the fewer the fish in the
water the less the concentration of pheromone present that suppress the
immune system.

The lower the stocking density the lower the bacterial load on the pond.

The offending pheromone can be removed with proper chemical and physical
techniques.

The importance of water changes should NEVER be under estimated. Regular
water changes will dilute the biological 'soup' the fish swim in. To
save water, utilize the pond water for watering the garden then supply
the fish and pond with fresh water. Both will benefit as will your
pocket. You will have created a mini ecosystem on your property.

The use of activated carbon has been shown to remove organic agents such
as pheromones.

Skimming the frothy bubbles or scum that forms on the surface of the
pond (Dissolved Organic Compounds or DOC) from time to time will also
lower the level of pheromones. The DOC should be removed from the system
and not simply skimmed back into the filter. The amount of scum or DOC
is important when the fish load is high. This should be removed from the
system.

A last consideration. Perhaps we should select and remove koi from our
collections regularly. As they grow and as we add new ones to the system
voluntary removing the old ones which are not of good quality will have
positive results.

1. The collection will be continually up-graded and improved.

2. The collection will be selectively 'culled' by the owner and not by
mother nature taking things into her own hands when disease breaks out
in overcrowded pond.
--





John Rutz
Z5 New Mexico

good judgement comes from bad experience, and that comes from bad
judgement

see my pond at:

http://www.fuerjefe.com