Keith, the two carved pieces I've seen....out in California if memory serves me, were done in basswood and the translucent appearance of the fins was accomplished with the painting. Misting a light haze of buttermilk colored white over the base colors can work wonders withthe translucent appearance. You'll need an air brush for that, although I've seen some beautiful acrylic work done on canvas of fish that show the translucent fins, and these were done with brush work.

Here's a picture of a carved one I found on the internet.....I'll try to get the URL of this ite up for you. OK, here it is
http://www.einsteins-emporium.com/life/decor/lds12.htm
Don't ask me how they crank these out for the prices they are asking...must be done in Sri-Lanka or ???????
Good luck, and PLEASE, keep us up to date on your progress.
Al