Help with crossing older fish.

Salvatore J.Sciascia sjsciasc at
Wed Dec 15 09:02:00 EST 2004


Hi Mark,

Older fish tend to become egg bound, so if you are not getting them to
breed  this could be your problem.  You may need to squeeze the blockage
from the  females before they will give you good eggs.  Also, if you are
not feeding  any source of live feeds you will want to do so.  Live feeds
such as Artemia  spp. will help with egg production and survival.  Plastic
plants are a good  stimulator for breeding behavior and may also help to
improve production.  As far as supplements, we used to use a small
concentration of potassium  iodide to help induce breeding, but there is
no evidence that it has any  effect.  One thing that does help increase
breeding behavior is giving fish  a shallow area to spawn.  We do this by
"tipping" our breeding cages at a  near 45 degree angle.  Males will then
try to entice females into the  shallow end for spawning.

Salvatore J. Sciascia
Zebrafish Facility Director
Molecular and Cellular Biology
Harvard University
16 Divinity Ave
Cambridge, MA 02138
sjsciasc at
p: (617) 496-8193
f: (617)496-3321
"marcuswrath" <rathmark at> wrote in message
news:cpklup$dr0$1 at
> --------------------------------------------------------------------------
> I'm having some difficulty spawning older brood fish, and I wanted to
ask this community if anyone has any ideas or suggestions to improve egg
production in aging zebrafish. These fish are between 2.5 and 3 years
old. Does anyone know of any effective suppliments or
> alternative feeds that could be used to help this situation? I'd also be
interested in any suggestions about the methods of handling and caring
for older brood fish. Thanks for any insight that you may have.
> Mark Rath
> Laboratory of Molecular Genetics
> National Institutes of Health/NICHD
> Bethesda, MD
> ---


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