 The total number of sperm whales in the world is unknown , but is thought to be in the hundreds of thousands . The conservation outlook is brighter than for many other whales . Commercial whaling has ceased , and the species is protected almost worldwide , though records indicate that in the eleven @-@ year period starting from 2000 , Japan has caught 51 sperm whales . Fishermen do not target the creatures sperm whales eat , but long @-@ line fishing operations in the Gulf of Alaska have complained about sperm whales stealing fish from their lines . 
