Dolphins at one time were hunted commercially. Some flesh and blubber were used, but the main product obtained was a fine-quality oil that was extracted from the lower jaw of the dolphin. Although the oil remains highly prized as a lubricant for delicate watch mechanisms, similar and cheaper products are available from other sources, and commercial dolphin fishing is virtually nonexistent. Many dolphins have been destroyed inadvertently by commercial tuna fishers using purse nets. A tuna boycott pushed U. S. tuna canners to agree in 1990 to buy tuna only from boats that fish in area where the dolphins and tuna swim separately.