sex ratio in zebrafish

Chi-Bin Chien chi-bin.chien at
Thu Nov 12 17:43:46 EST 1998

Dear Fangjun,

>In my lab, male zebrafish is predominant in the population.
>The sex ratio is about 4:1 (male : female), is it a normal
>result or something wrong happened in the breeding course?

This is (unfortunately) quite common in raising zebrafish, that's what you
get for working with an animal without sex chromosomes. Sex is apparently
determined by a mixture of environmental and genetic factors, but the sex
ratio distortion can become especially bad when the fish are inbred too
much. So you should try to maintain the genetic diversity of your wildtype
stocks, by keeping each generation relatively large, and mixing many (5-10)
clutches to go from one generation to the next. If it gets worse you should
try to get wildtypes from another lab and cross them into your stocks.

Good luck,
Chi-Bin Chien

< Dept. Neurobiology and Anatomy |       office: 1-801-585-1701 >
< Univ. Utah Med. Center         |          lab: 1-801-585-1702 >
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< Salt Lake City, UT  84132      |   chi-bin.chien at >

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