question about zebrafish breeding

Dr Peter Cattin p.cattin at auckland.ac.nz
Mon Nov 5 10:49:44 EST 2001


Hi Dallas,

Thanks for the very interesting summary.  The biokinetics of a 
biofilter are certainly more than "2 dimensional".  Chemical stress 
on any high density biological "factory" would be extremely subtle 
and hugely complex as your comments below infer.  Apart from the 
metabolic wastes, there are also the chemical biproducts of the 
breakdown of the uneaten feed - so it ends up being a fairly soupy 
porridge of which, as you quite rightly point out, we only monitor a 
few of the more toxic components.  

It would be great to read the article on the goldfish also.

Cheers and regards,


Peter

--
Peter Cattin PhD
Division of Molecular Medicine
Faculty of Medical and Health Sciences
University of Auckland
Park Road, Grafton, Auckland.
Private bag 92019, Auckland,
New Zealand.

Tel: +64-9-373-7599 xtn. 6373
Fax: +64-9-373-7492

"Dallas Weaver, Ph.D." wrote:

> in article 9qfign$alm$1 at mercury.hgmp.mrc.ac.uk, Dr Peter Cattin at
> p.cattin at auckland.ac.nz wrote on 10/15/01 1:55 PM:
>
> Peter,
>
> The goldfish pheromone work was done  at Oak Ridge National Lab in
> the 70's and I can't find my copy of the report.  I seem to remember
> that it was part of a MS Thesis.  He used a crude extract
> (eliminating ammonia and the other common waste products) from high
> density fish water and showed impact on respiration, heart rate,
> metabolisms rate, etc.
>
> The point about the bacterial habitat specifications(ie filter
> surface area and mass transfer requirements) becomes very complex
> when you start trying to understand what is happening to the waste
> components other than the ones that you can easily measure (ie.
> ammonia, nitrite).  With pure ammonia feed and only enough P, K, and
> Fe for the bacteria, you can get ammonia oxidation rates in the 1 to
> 2 gm/m2 day range, on most thick film media.  However, with real
> fish waste (that contains a lot more that just ammonia) the rates
> are down by a factor of 5 to 10 on the same media at the same
> substrate concentrations.  This is related to competitive exclusion
> and related problems where the faster growing bacterial species
> (using either more degradable substrates and/or higher concentration
> substrates) out compete the slower growing bacterial species for
> habitat in the biofilms.  This same phenomenon occurs in industrial
> waste treatment where you have something easy like benzene mixed
> with water with something that is more refractory like MTBE (methyl
> tert butyl ether -- a gasoline additive that contaminates
> groundwater).
>
>
> This subject get into the details of the system design and whether
> the biomass and/or the water are operating plug flow or a mixed
> reactor.  We have a indication from some species of animals that
> reproduction is better when we have enough internal surface area to
> eliminate competitive exclusion problems.  We also have some
> indications that some either very low concentration or refractory
> components with bacterial kinetics slower than ammonia/nitrite may
> be relevant the the animals performance in tightly closed systems.
>
> Pheromone and other trace waste products are a relevant questions
> after ammonia is not an issue.  I assume that any well designed
> research system will not have any ammonia problems.  Even in
> commercial systems, ammonia should not be a problem.  Our recycled
> water is normally < 0.1 ppm ammonia (N) (ie ND on our equipment) at
> all times.  We also expect nitrite to be < 0.02 and if it isn't it
> is time to check out the system (a management action set point).
>
> I did the growth experiment at 28 C only because one of my customers
> was using 28 C.  I also did an experiment at 22 to 24 C (variable
> ambient) with an egg to egg time of 65 days.  I know 22 C is a bit
> on the low end of the growth curve.  You only get the advantage of
> 28 C growth rate if you have the food (bioenergetic aquaculture
> models provide some useful concepts relative to this problem -- at
> high enough temperature the animal can have maximum feed rate with
> no growth).  With the less than ideal feeds, lower temperature in
> the 25 C range with give adequate growth rates with fewer problems
> and it will be more comfortable for the staff.  My commercial zebra
> production runs an egg to egg time of about 90 to 100 days at 22 to
> 24 C with most of the growth being on dry feed at densities >
> 75/liter.
>
> Dallas
>
> Dallas E. Weaver, Ph.D.  <deweaver at get.net>
> Scientific Hatcheries
> 5542 Engineer Dr.
> Huntington Beach, Ca 92649 USA
> 714-890-0138
> Fax 714-890-2778
>
> > A point in your comment, Dallas, that I think is non-sequitur. 
> > There is no doubt that maximum growth requires optimal water
> > quality, and that an important part of this process is the
> > provision of an adequate substrate (space) for the bacteria 
> > required to remove metabolic wastes etc.  It would be reasonable
> > to assume that an inadequate supply of these bacteria will
> > negatively impact on the growth rate and general health of the
> > fish.   I would suggest though, that the relationship between an
> > inadequate supply of denitrifying bacteria and goldfish producing
> > growth inhibiting pheromones is pretty tenuous.  A single fish in
> > a large volume of poor quality water will not grow well without
> > pheromones.
> >
> > Do you have references on the goldfish pheromone phenomena as I
> > would like to read about it?
> >
> > Finally, you have remarked on the "why 28oC temperature" for
> > growing zebra fish - which is a point that was puzzling me, yet
> > there does seem to be some truth in the excellent growth rate of
> > zebra fish at this temperature.  Any ideas as to why?
> >
> > Thanks and regards,
> >
> > Peter Cattin
> > --
> > Peter Cattin PhD
> > Division of Molecular Medicine
> > Faculty of Medical and Health Sciences
> > University of Auckland
> > Park Road, Grafton, Auckland.
> > Private bag 92019, Auckland,
> > New Zealand.
> >
> > Tel: +64-9-373-7599 xtn. 6373
> > Fax: +64-9-373-7492
> >
> > "Dallas Weaver, Ph.D." wrote:
> >



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