You'll need to stand ON the boat to have Feren reply to your hailing him.
After asking him "who is razortooth" I would jump off the boat and do "F8" under the boat , usually facing just to the right of the island (stay away from island ; tigers aggro into water and dont hit tigers back or the kerrans will also aggro-just try to zone.) Anyway if you target Razortooth or a spikefish, DONT lose the target! use your range weapon or cast a long range damage spell to pull. I just keep trying to cast untill the fish is in range. Spikefish spawn every eight minute or so.
Ive killed at most three spikefish before Razortooth spawns. I dont know Razortooth respawn time because I never stick around afterward but spikefish spawn one at a time and seem to be place-holder for Razortooth. After killing a spikefish, med up and go kill that rat INSIDE the hut for the fish-bone necklace quest(good exp for low to mid teens - it hits hard though). Med up some more and look for Razortooth again.Razortooth is mid-teens and spikefish are easier. I have done the fishingpole quest three times for my characters (it is FAST and good in duels with casters my strength is at 87 and I strike with consistant 8pt hits)Of course it isnt a great weapon , but I think its a must have. good luck!