Many fish stocks targeted by fishermen are also a primary food source of marine mammals. Normally this would be viewed as competition for a common resource. With the passage of the Marine Mammal Protection Act (MMPA) in 1972, marine mammals are protected which has aided in the recovery of numerous species. Along the West Coast, the MMPA has been highly successful in the recovery of most stocks of California sea lions and Pacific harbor seals, and it has resulted in more frequent interactions with commercial and recreational fishermen, causing damage to fishing gear and loss of catch. Non-lethal methods to eliminate or reduce pinniped predation have been unsuccessful. This paper summarizes the issue of marine mammal depredation in general, examines some of the economic damages, and discusses efforts to minimize these interactions.