[Zbrafish] Fish/larvae/juveniles mortality!

David G. White via zbrafish%40net.bio.net (by dgw5079 from u.washington.edu)
Tue Aug 31 12:12:55 EST 2010

Hello, this is a unfortunate and odd situation, difficult to diagnose from a far. Given what you have told us I would lean towards an issue with the water. I am sure your keeping the fish water at known water quality parameters but is it fluctuating drastically with in those parameters or does your house/source water fluctuate particularly pH and conductivity/salinity? My first guess would be osmoregulatory stress, do the fish ever seem dizzy (disequilibrium)? On your multi-rack fish system does mortality seems to occur more on some racks versus others? Are you using a dosing system to control water parameters?   When your filling your nursery cups is the water the same, source and water quality? What is your typical dissolved oxygen readings? I would start testing water in different locations in a tank that recently died, in a tank that survived, in different sumps, your source water and your source water after its been conditioned for system water.

David G White
Research Coordinator
HSB Zebrafish Labs
University of Washington
Department of Biological Structure
HSB G520 Box 357420
1959 NE Pacific Street
Seattle, WA  98195-7420
Tel. 206-685-7512
FAX 206-543-1524

On Mon, 30 Aug 2010, Vishal wrote:

> Hi There.
> I would like to have your opinion about an incidence happening in our
> zebrafish facility. In last couple of months, we have been noticing
> that all adult fish or larvae/juveniles die in their tanks or nursery
> cups, respectively while fish/larvae/juveniles in adjacent tanks or
> cups stay perfectly fine. We have linked circulatory system with 10%
> water replacement everyday. We are puzzled to see why fish/larvae/
> juveniles die in some tanks and other tanks in the same system do
> fine. Also, it happens very quickly (within hours) without any
> symptoms of sickness. I am wondering if anyone has ever noticed
> something like this and could help us figuring out what might be going
> on. Is it related to some water parameter or some parasitic infection?
> Any help in this regard would be greatly appreciated.
> Thank you,
> Best regards,
> Vishal
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