Fish larvae (and mostly also juveniles) are too small to draw blood. Can anyone point me to literature how to assess stress levels in fish larvae not involving RNA/DNA ratios?
I am not sure if this procedure (Ellis et al., 2004. A non-invasive stress assay based upon measurement of free cortisol released into the water by rainbow trout. Journal of Fish Biology, 65: 1233–1252) would work with larval fish but it might if water volumes were small enough.
You could probably do whole body cortisol. Of course its terminal, and you may need to pool several larvae to get enough tissue. If you google it you will get several references, especially on zebrafish. Good luck.
I'm not sure, but some statistical procedures can be useful. In this case look, please, our article: "Application of the " Ast " traps for study of some environmental factors' Effect on juvenile fish".