Ya don’t want it to run away? ARK mobile players can use a pteranodon, or anything else that can carry the otter, to pick it up and bring it to an enclosed space in your base. There, you can feed it fish.
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
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.