Knocking it out with a cannon is easier, but will cost you 30 taming effectiveness. Choose wisely. Also, only aim for the head/torso. Hitting it's limbs will NOT induce torpor, and may kill it if you hit them too many times.

My "trap" for a 140 consisted of 3 large bear traps, me running for my life, and a stone foundation with a cannon on it in front of them. Then I just adjusted it and it knocked on the first hit.

Chain Bolas and Nets can also immobilise Karkinos. You can also use catapults to knock it out. If you don't have any kibble, you can give it spoiled meat.