Either a next generation HBG, or a Green Sunfish is my guess. It could also be one of the original HBG stockers that didn't grow too much??

I'm noting the blue lines near his eye, and the the yellow "anal" fin.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."