The coastal economy was largely based on fishing. Salmon, halibut, euchalon and herring were caught with nets, lines, spears, traps and weirs. The Nootka and Makah tribes also hunted the whale. Northern tribes used nets to catch deer and elk, while more southerly people hunted antelope and rabbit. The coastal climate was too foggy and wet for maize agriculture, but people gradually learned to practice such techniques as transplanting, seeding and field burning that improved the yields of indigenous plants. They also cultivated a modest amount of tobacco. Advanced tools were made from obsidian, jade, copper, amber, whalebone and shells. The adz, made of nephrite, was developed as a carving implement. In later years, resourceful natives used iron from Japanese ships that wrecked on American shores. Boxes and hats were carved from shell and slate; blankets, baskets and hats were woven on an upright loom from cedar bark and mountain goat hair. The people of the Pacific Northwest were involved in a great deal of trade. Chinook tribe members acted as middlemen in the exchange of goods between coastal and Plateau tribes. Small dentalium shells were used as standard objects of barter. Some tribes hosted annual trading festivals, where people of all tribes would come to swap goods. When white seamen discovered the area, a vigorous trade sprang up between the natives and the newcomers. The indigenous people eagerly traded blankets and other commodities for large panels of hammered copper.