Is there an adhesive that could used for larval fish?
You could try methyl cellulose, which my lab and others use. It's not exactly an adhesive, but it is quite viscous. It's common enough that it's in the Zebrafish Book: https://wiki.zfin.org/display/prot/Methyl+Cellulose+Mounting . Obviously, be sure whatever you do is approved by your animal care and use committee.