Chil Bo San No. 6 is a shipwreck on Spray Cape, a conspicuous headland on the west coast of Unalaska Island between Skan Bay to the north and Pumicestone Bay to the south, about 85 miles (137 km) northeast of Nikolski and 32 miles (52 km) southwest of Dutch Harbor, Alaska. The cape was named by the U.S. Bureau of Fisheries in 1888 after the Russian name “Mys Mokrovskoy” meaning “wet cape”. From Spray Cape, the shore trends south for 3.5 miles (6 km) to the entrance of Pumicestone Bay. Unalaska is in the eastern Aleutian Islands and is the second-largest island in the Fox Islands group, after Unimak Island. The highest point is the active Makushin Volcano with an elevation of 6,680 feet (2,036 m). The coastline of Unalaska is markedly different in appearance than other major Aleutian Islands, with numerous inlets and peninsulas. Aleut Unangan people have lived on the island for at least 10,000 years. The island was first seen by Europeans in 1741 when Vitus Bering sailed by on the Second Kamchatka expedition. In 1759, a Russian settlement was constructed but four years later it was destroyed by the Aleuts. The attacks claimed the lives of 162 Russian settlers. This event triggered bloody reprisals against the natives. By 1787, the Russian colonists used many Aleut seal hunters as forced labor to hunt sea otters and seals for the maritime fur trade. In 1788, the Spanish expedition of Esteban José Martínez and Gonzalo López de Haro explored the coast of Alaska as far as Unalaska Island, marking the farthest west the Spanish ever explored in the region. In the same year, English explorer James Cook visited the island, and spelled it Oonalashka in his journal, after the Russian name.

On 21 January 1985, the Chil Bo San No. 6, a South Korean fish carrier of 285 feet (86.9 m) and owned by Wonyang Fisheries was reputedly sinking in the Bering Sea approximately 200 nautical miles (370 km) northwest of Adak Island in the Aleutian Islands. Another South Korean vessel rescued the crew of 29. When the ship remained afloat, the crew reportedly returned and brought the vessel back to South Korea. On January 11, 1989, Chil Bo San No. 6, reported itself in distress on the west side of Unalaska Island, about 2 nautical miles (3.7 km) south of Spray Cape. The vessel had a broken propeller shaft and was drifting towards shore in severe weather conditions. When the ship floated into shallow water the crew lowered both anchors to try and catch the bottom, but both anchors dragged over the rocky nearshore shelf and the vessel grounded two miles (3.2 km) south of Spray Cape. The vessel was carrying 4,565 gallons (17,280 l) of lube oil in drums and tanks, and approximately 65,000 gallons (246,000 l) of diesel. Two U.S. Coast Guard helicopters and a lifeboat from the fishing trawler Pung Yang Ho rescued the crew of 54. On January 15, an oil sheen had developed around the vessel and extended 2 miles (3.2 km) south. The vessel eventually floated over a reef and beached in a small cove, then settled onto the rocks sideways and broke apart. Due to its isolated location and inclement weather, an immediate response to the wreck was not possible. The following summer, the vessel owner removed roughly 4,000 gallons (1,514 l) of lube oil and 500 gallons (1892 l) of diesel, with the balance of the oil lost to the environment. The vessel was also infested with rats that survived and established a population on Unalaska Island.

In the summer of 1990, salvage crews from Dutch Harbor found thousands of rats living in the shipwreck and many had come ashore. The brown rat, also known by many other names including the common rat, street rat, sewer rat, wharf rat, Norway rat, is a geographically widespread species thought to have originated in northern China. This rodent has now spread to all continents except Antarctica and is the dominant rat in Europe and much of North America. Rats likely arrived in the Aleutian Islands on Russian ships in the 18th and 19th centuries. Brown rats are omnivorous and have a devastating effect on the native birdlife. However, the Chil Bo San No. 6 shipwreck was not an environmental catastrophe because a rat population was already well established on Unalaska Island. But the incident underscored how rat introductions occur and threaten bird nesting habitat even on remote islands. Invasive rodents can be particularly devastating in Alaska, which hosts nearly 95% of seabirds, and nearly 50% of all of the shorebirds that occur in North America. Several of these species and sub-species breed only in Alaska, and eight seabird species nest nowhere else in North America. The state also harbors a number of endemic birds and mammals. Endemic species are especially susceptible to decline due to their relatively small population sizes, use of restricted resources, and a high degree of specialization, making them less able to cope with change. For centuries, most of the islands in western Alaska were not home to any non-human mammals, making them ideal nesting and feeding grounds for large congregations of birds. The purposeful introduction of nonnative mammals, such as fox, and inadvertent introductions of rats, have already led to severe degradation of some island ecosystems in Alaska. Mainland ecosystems are also at risk from rodents, as increased numbers of shipping lanes and harbor developments have opened new pathways of introduction to coastal areas and cities across the state. Preventing the further introduction of nonnative species, particularly voracious predators like rodents, is a high priority of the U.S. Fish and Wildlife Service, Alaska Department of Fish and Game, conservation groups, and Alaska Native organizations. Read more here and here. Explore more of Spray Cape and Unalaska here: