The dorsal fin, on the top of a fish’s body ... The lateral lines are the final section in our guide to basic fish anatomy.

Fins: Help a fish move. The top fins are called dorsal fins. If there are two dorsal fins, the one nearest the head is called the first dorsal fin and the one behind it is the second dorsal fin.

Evidence for this function first came from studies of the organ's anatomy and its nerves as well ... Its teeth are designed not so much to grab or slice fish but to prevent them from escaping ...