HELP! They stopped breeding!

[Paul Z. Myers]

In article <D2LtJ2.CI4 at murdoch.acc.Virginia.EDU> Lisa Lynn Cunningham,
llc4q at galen.med.Virginia.EDU writes:
>I have a breeder colony of about 60 zebrafish who have been
>giving me nice clutches of eggs pretty much whenever I needed
>them.  Suddenly yesterday and today, no eggs! Is this common?
>Are they possibly being over or underfed? I give them TetraMin
>flake food once or twice a day and a few brine shrimp once every
>day or so.  Their tanks are always clean, temperature is 28C.
>I did have a power failure day before yesterday which caused
>their lights to be about half an hour late coming on -- would
>this cause them to stop laying eggs? What can I do to get them
>to breed again? I siphoned the bottoms of their tanks, and
>there were 24- and 48- hour embryos in there, as well as lots
>of young fry, so I know they've been laying eggs in the past
>several days.  Any suggestions would be appreciated! I need
>those embryos!
>

Are you collecting eggs from all your tanks, all the time? 
The fish can get exhausted if you've got them on marbles
all the time -- it's a good idea to have them on a rotating
schedule.

The fish can be finicky about the light cycle. Flashing a light 
on them in the middle of their night can mess up their 
schedules pretty thoroughly, but I wouldn't think a half-hour
delay in their dawn would be that traumatic.

I do get these annoying dry spells in egg production as well.
My solution has been to pull the marbles from the low fecundity
tanks to give them a rest, and to swap around males and females.
A bit of variety in their partners seems to spark up a little
more romance :-)

------------------------------------------------------------
Paul Z. Myers                    myers at astro.ocis.temple.edu
Dept. of Biology                              (215) 204-8848
Temple University
Philadelphia, PA 19122