[Zbrafish] In vitro Fertilization

[lionel.aubergat from laposte.net]

Hello,

I'm a French Master student (of research)  and I work in a laboratory
of uranium toxicology. I'm working with zebrafish and I would like to
fertilize eggs with an in vitro method. In the website "zfin.org" it
was explained this fertilization.
I have tried to do this fertilization but it did not work.
When I gently squeeze female, I only get 4 eggs and for the male, I
have never get sperm. So I have killed the fish and removed gonads. I
have put them in a hank saline solution and I have dissociated testes
with pestle. But when I have put the sperm on the eggs, I have added
water to activate the sperm but I have never seen fertilization (after
1 hour).
Can somebody know how to fertilize eggs with this method ?

Best regards

Lionel