How about we do that but allow Shade's suggestion: summoning them in air and lighting them? Since they're not aquatic, they probably don't have to be summoned in the water.
Ok, I don't even need the summoning bit if we write in that they can burn like alchemists fire. I guess really like a flask of oil, taking a full round action to light.
I now have this mental image of some PCs fighting trolls or ogre magi, running out of fire weapons but recognizing all the "fish" swimming around near them.
Ok, then, just take Cleon's basic stats and add
Flammable (Ex): A black burner (alive or dead for no more than 1 week?) burns easily due to the special oils in its flesh. If lit carefully, a black burner body corpse can be kept burning as a small fire for up to X hours. If lit quickly, a live or dead black burner can be lit and thrown as a splash weapon as a full-round action, following the rules for alchemist's fire otherwise.