What would the result be when identifying a fish with a single dorsal fin, no fin on its back near the tail, and a tail that is asymmetrical?

The characteristics show that the given fish is a sturgeon.

Sturgeon is a general name for the twenty-seven fish species belonging to the family Acipenseridae. Their origination dates back to the Triassic, that is, about 245 to 208 mya.  

The sturgeons are late developing, and long-lived fishes with different features like a heterocercal caudal fin identical to that of sharks, and an elongated spindle-like body, which is scaleless, smooth-skinned, and armored with five lateral rows of bony plates known as scutes.