Hello.
We are currently trying to get a little experience with various zebrafish protocols. Our goal at the moment is to maintain a zebrafish population capable of producing a modest number of embryos ( about 500/week). Most husbandry protocols recommend keeping 1 male in the female tanks to stimulate reproductive hormones; this implies the other males are usually kept separate.
Is it ok to house a stock of 20 fish (10 males + 10 females) in a 40 liter tank, or will this lead to uncontrolled overspawning and exhaustion?
We used to keep males and females together all the time and got good reproductive outcomes.
Good luck!
Jo
We also keep males and females together, and they produce a great quantity of embryos.
Best!
i've been in labs that do either options and with both setups we got good egg production (comparing WT crosses here)
i don't know how much experience you have with zebrafish, but one advantage if you keep males and females separate is that it might be easier to recognize the sexes (better for inexperienced students), although you have to cross them regularly so the females don't get too big.
We keep males and females together, but what I see as problem is the volume of water in which you keep animals: 40l tank is too much for only 20 fish! Zebrafish are social animals and having low density population will affect their behaviour (including the breeding). There are 2 main way of thinking in the zebrafish community: the 'american' one, by which the density is 10 adults/l and the 'european' one, by which the density is 5 adults/l.
There are multiple issues to consider in response to your question, some of which the others have already eluded to.
keeping your animals housed together will result in uncontrolled, natural spawning in your tank. This is normal and healthy, and generally doesn't cause reproductive issues unless you are running your fish hard. As you state an interest in only harvesting about 500 embryos per week, then you shouldn't have any problems, if even only 2 pairs lay each week, you should still get ample eggs spawned.
i wouldn't worry too much about your light stocking density, Castranova et al. (2011) suggest that density has a negligible effect on reproductive success.
Given that you are running a small colony in a single tank, I suspect your colony will be made up of sibling fish, particularly if you have sourced your animals from a pet shop, or from another facility if you didn't specify specifically against related animals. Zebrafish are a highly olfactory dependent species, and while preferring the security of sibling presence during larval development, often actively avoid sibling courtship if they can.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3180766/
According to the experience we had, you can keep both sex together, and also isolate males. What you can`t do, is to isolate females because they migh stop spawn eggs....
I think 20 fish equal gender ratio is fine. Similar to nature. I do not know your tank setup but bigger tank volume generaly means less problems with spoiled water if you happen not to have flow thru system. I saw colecting around thousands embryos every second day from similar systems. Food and water quality might be more important than sex ratio and water volume.
@Solange Ibarra what do you mean by dont isolate the females? Do you mean dont have a tank of soley female zebrafish or dont house one individual female fish by herself?
- thank you