Read this, it might help you:
1: The best place to encounter tuso is 90-91 lat and cover all longitude from red ob to the end of herb Island.
2: Don't solo search, make a party and cover full bottom of the map.
3: Don't search in shallow water and surface, go for mid and deep sea.
4: They need to grab your tame then only can they be tamed.(Take Carbonemys with health and speed pumped)
5: They take 50 black pearls per serving.
6: They only agro in deep sea.
7: Last and the most important, the server must be brutal or their chance of spawning is not that much. Put server to brutal and for one day atleast go killingspree in ocean to open spawn spots for tuso.
8: Pump only melee and health to tuso.
I tamed a mosa for the very specific reason of taming this bastard. Met one and almost shat my pants because it is so fast on mobile, at least. Do not engage without a plan to tame this bastard. Better get your scuba set and spare lazarus chowder, just in case the craplegs grab you too. Go fishing for black pearls, I am lucky enough for one to actually get a ton only by fishing and killing some ammonites ( exp grinder for my mosa). Trapping is not possible, and will follow you anywhere max speed, on mobile that is. These bastards have no invisible walls or whatnot, only go through every rock you know in hopes of trapping it, then here goes either taming or killing. Best thing to use is a ton of black pearls, and a soothing balm on mobile. Remember, don’t get caught or your dead meat, especially if near the world borders (as these bastards tend to spawn more near the border) and put some speed into your mosa. Plesiosaurs or mosas can outrun this thing, only problem if your stam ran out.
Don’t believe the comments saying you need 2 minimum tribe mates to tame this. It can be easily solo tamed i like to use two turtles one to sit on and one for bait. Let it grab the bait turtle then feed the tuso and jump back on your safe turtle and whistle the bait turtle back and just repeat.
You need two people, one for feeding the black pearls and the other to feed the turtle that is in the grasp of the Tusoteuthis, with sweet vegetable cake for the health and to feed it stimulates berries as well
I found a way to tame the beached ones on crystal isles that dont want to be tamed, I bit it and waited a minute and bit it again and it grabbed me that time allowing me to tame it. Sorry I dont have more info yet