Danio Dilemmas!

[eb0u81ab at liverpool.ac.uk]

I am a third year student at The University of Liverpool and currently 
undertaking my dissertation. The subject of this is mating patterns 
in wild-type Zebra Danios under differing sex ratios in a population. 
Still being at the planning stage of this project I have come across 
a problem to which I hope someone can give an answer or perhaps 
guide me on. 

Being wild-type danios I plan to have a population density and sex 
ratio in accordance with their native environment so as to not 
stress the fish into changing egg-laying potential and biasing 
result. So far this information, or even an estimate has eluded me.  
I wondered if anyone may be able to help at all.  

Jules Howard.