embryo decrease

Folks,

We had a student who was doing a project using Zebra fish embryo's
this summer.

At first he got pretty good embryo yields but as this semester
progressed he got less and less until we got almost none at the end of
this semester. The fish were fed well and we should have had fairly
good water so I am not sure what was the problem. Do the fish just
slow down over time and you have to start with fresh fish or fish that
are kept under different light conditions?

We had 14 light and 10 dark and put in a trap when we wanted to
collect embryo's and we had about 10 adults for each of two tanks.

I am a little worried because we have a student who will be doing this
again in the Fall and we would like to be sure that we get plenty of
embryo's. Any suggestions on how to keep the numbers of embryo's
high?

You can respond directly back to me at [Only registered users see links. ] or to the
list.

He used the following setup:

The test organism for my project was Danio rerio. The fish were
acquired from the Dordt College biology department who originally
obtained them from The Dog House Etc in Sheldon. The fish were housed
in two separate tanks to help increase embryo collection numbers. Each
tank was approximately 10 gallons and was maintained at around 28.5
degrees Celsius for optimum embryo production. The fish were fed a
rotation of fish flakes with brine shrimp or with blood worms. This
diet encouraged more vigorous embryo production. It was better for the
fish to be fed less food at more frequent intervals. The fish were
maintained and bred according to accepted methods in The Zebrafish
Book (Westerfield 2000). Frequent water cleaning (rotation) promoted
embryo production. I changed over half of the water on a weekly basis
(Westerfield 2000, Warolin 2002).