For full Otter taming details, get the taming calculator app.
To tame an otter, kill some fish, approach the otter, and then use the action button to feed the fish to it. Level of fish does not impact taming. The Sabertooth Salmon is by far the most effective fish, followed by the Piranha and the Coelacanth. Please ignore timing and effectiveness as calculations are not yet complete.
It is tamed in the same way as the Hesperornis, where you have to carry a dead fish to it. Larger fish, and those caught by Ichthyornis, apparently work better. Piranha are better than coelacanths for taming, and salmon are better than piranha.
Their a rare/ uncommon spawn. They are mainly found down south in max of a pair of two. But their usually found alone. They are a passive non-agressive tame that wont flee. (They wear hats too). Have fun!
Just push this cute lil creature in front of a giga and it'll have an existential crisis. Realising the path of destruction it left in its wake and deteriorate in front of the otters blue sparkly marble eyes