The otter will not gather pearls on aggressive you have to command it to attack 1 at a time. Also mine seems to be glitched after eating a fish it will follow a random tribe mate or try to run back to base idk if anybody else is having this problem but I'm getting tired of chasing it after every fish.
I once had an otter that I named harry otter , he was a great otter he got me all the silica and black pearls I needed, he once saved me from a megalodon , he kept me warm to, he was a great companion I took him almost everywhere,but one day I was farming pearls with him I threw him at a fish to get pearls from it but instead he disappeared I looked and looked for him only to not find him but uneven got a message that he was dead, he's still out there somewhere, I still look for him to this day. #prayforharryotter
Do not take it with you if you are in danger of getting knocked out as it will get thrown off your shoulder if you fall unconscious, leaving a squishy pet vulnerable to whatever is attacking you - in my case, eurypterids.