We don't imagine bears have ever spent a long time talking to humans, and so the nuances of the human voice are lost upon them. The fishermen did their best, though.
In the same way that a pet owner talks to a scared or distressed dog, the fishermen tried to calm the nerves of the bear by speaking to it in gentle tones. They were telling the bear that they were there to help, but did the bears understand? More importantly, did the mother understand?