[Zbrafish] Sex-Bias & low production

[dmerlo At deakin.edu.au]

Hi Judy,
As Jason mentioned, I have also seen a drop in egg production due to a  
dominant female(s) in breeding tanks in different facilities. It can  
help to jumble the fish about, or even just adding a few different  
females and/or removing a few can usually reinstate breeding. The age  
of the breeders and the regularity of their use can also affect their  
laying capacity. Fish that are crossed regularly (ie more than once or  
twice a week) will generally cease reliable egg production earlier  
than those who are bred less often, ie once or twice a week. How old  
are your breeding fish? I've found that fish used for regular egg  
production stop producing consistent and reliable numbers of eggs  
after around 12 to 14 months (although may produce some eggs long  
after this time). It may be worth checking.

Hope this is of some help

Daniel Merlo
Deakin University, Burwood.


Quoting Judy Bennett <jbennett At bio.umass.edu>:

> Hi All,
>
> We've been experiencing decreased egg production in one of our fish
> facilities.  It has stalled some experiments and we're looking for ways
> to get the fish back on track.  We do use a mass mating system for our
> WT lines and those tanks have been producing consistently, although we
> don't know how many of the males are doing the fertilization.
>
> I have not seen any problems with our water quality, and two other
> facilities using the same feed have been doing fine (ZIRC recipe).  At
> the moment I have increased the water exchange, am going to try a new
> dry feed and have increased the amount of brine shrimp we feed out
> (although I'm worried about overfeeding at the same time).  The PI
> thinks it correlates to the female sex bias in the facility- leaving us
> with fewer males that may not be potent.  He is interested in bringing
> in a male bias line to see if it will help the problem.
>
> -Could bringing in a male-bias line help and/or does anyone have fish
> they could possibly send?
> -Is there a guideline for the amount of brine shrimp to feed per a
> certain number of adult fish
> (X mls/1000fish)?
> -I also suspect a certain amount of inbreeding, but haven't found any
> information about when it could start to affect gonad
> development/spawning.
>
> Thanks for any help/information you can offer.
>
> Judy Bennett
> UMass Amherst
>
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