High female rate

christian lawrence clawrence at rics.bwh.harvard.edu
Tue Apr 5 11:31:00 EST 2005



What are your densities (fish/liter) when you are raising your fish?   In
some cases, zebrafish reared at lower densities often show a female bias
in the sex ratio.  If you are growing the fish up under these conditions,
you may be skewing the sex ratio towards females.  If this is the case,
you may be able to alleviate your problem to some degree by increasing the
density of fish in your rearing tanks.  It may take longer for the fish to
mature, but getting a greater proportion of males would be worth the wait.

Sex ratios can also be skewed in one direction or the other if the strains
are very inbred. However, if you are crossing fish from your facility with
fish from other facilities (and presumably different backgrounds) and you
are still seeing a consistent female bias, then it is likely an
environmental factor that is causing your sex ratio problems.

Christian Lawrence
Brigham and Women's Hospital
Karp Family Research Laboratories 06-004B
One Blackfan Circle
Boston, Massachusetts 02115
Tel: 617.355.9041
Fax: 617.355.9064

-----Original Message-----
From: owner-zbrafish at hgmp.mrc.ac.uk
[mailto:owner-zbrafish at hgmp.mrc.ac.uk]On Behalf Of Tohru
Sent: Tuesday, January 04, 2005 6:37 PM
To: zbrafish at net.bio.net
Subject: High female rate


Hello. We have high female rate from crossings (wild-type x wild-type,
mutant x wild-type, or any; our own crossings and embryos from other
facilities) like 0 - a few / 100 fish that makes it difficult to breed
fish. We raise babies with paramecia, brine shrimp and then flake
food. Any ideas? Thank you. -- Tohru


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