The captain had the heaviest responsibilities of any member of the crew. He was responsible to the owners for the ship and all the goods aboard it, and although he kept up a correspondence with the agent while at sea, the length between communications meant the captain had to make most of the important decisions for his vessel on his own. The captain was in charge of charting a course for the ship. He used his knowledge of ocean currents and migration patterns to predict when and where he could find large groups of whales. He used maps, charts, and navigational instruments to steer a course, made decisions about when to lower the boats in pursuit of a whale, and when and where to stop to make repairs to the ship or take on fresh supplies of food, water, or building materials. The captain was responsible for keeping order and enforcing discipline aboard a ship. He acted as judge and jury in disputes between members of the crew. He also acted as the ship's doctor. Captains were typically but not always, white men of Yankee stock, who had served aboard a ship since the age of about 12. Captains often became owners, and many amassed substantial fortunes. Aboard the ship, he was often a lonely figure, who kept aloof from the rest of the crew in order to maintain his authority. Of all the crew, he got the largest percentage of the profits. His lay was between 1/8 and 1/16.