Fishermen play a key role in the endangerment of sea lions. Sea lions rely on fish, like pollock, as a food source and have to compete with fishermen for it. When fishermen are successful at their job, they greatly reduce the sea lion's food source, which in turn endangers the species. Also, human presence and human recreational activities can cause sea lions to engage in violent and aggressive actions. When humans come closer than 15 meters of a sea lion, the sea lions' vigilance increases because of the disturbance of humans. These disturbances can potentially cause sea lions to have psychological stress responses that cause the sea lions to retreat, sometimes even abandon their locations, and decreases the amount of time sea lions spend hauling out.