Sharrac Teeth

You obtain it from the Murkray fish.

Murkray can be found by the coast and sea, south-west and south-east of the cetus gate and require peppered bait or twilight bait, which can be obtained from fisher hai-luk, by reaching the rank visitor and costs 500/2000 standing.

It is still possible to fish a Murkray with peppered bait, which can be obtained for 500 standing. In that case, the spawn is not guaranteed but still more affordable.