Fauna. Pacific salmon spawn in nearly all of the watersheds on the territory of the sanctuary. These include pink, chum, coho, kundzha, and loach. Chinook salmon are numerous in the Ozernaya River. Kuril Lake is the largest sockeye spawning area in Asia.  

Marine fauna is typical for the coastal waters of southern Kamchatka. The Siberian salamander is the only amphibian in the reserve.There are no terrestrial reptiles, but a leatherback sea turtle was seen in the waters off Lopatka Peninsula.  

Bird fauna in the sanctuary is original, and numerous migratory routes cross its territory. In the fall, birds arrive here from the eastern and western coasts of Kamchatka, and in the spring, the sanctuary is a stopover area for migrating birds heading north along the Kuril Islands, where their routes divide into the western (Sea of Okhotsk coast) and eastern (Pacific coast) routes. While not all bird species have been registered, thus far over 170 species have been identified, of which 100 nest here. Thirty six species and subspecies of birds are listed in the Red Data Book of Kamchatka, and 17 are in the Red Data Book of the Russian Federation. 

The composition of bird species is common for the Peninsula. Some migrants include species nesting outside their traditional range and sometimes even in North America. 

About 10 pairs of Steller’s sea eagles nest in the reserve, along with as many as 12 pairs of peregrine falcons. Over 50 colonies of coastal birds are found in the sanctuary. 

Gyr falcons winter here and, along the coast, thousands of Anseri formes, eagles, and auks also over winter. The largest colonies are in Pervy Kurilsky Bay between Lopatka Peninsula and Shumsha Island. 

Mammal fauna consists of 44 species, 13 of which are listed in the Red Data Book of Kamchatka and seven in the Red Data Book of the Russian Federation. Most of the rare animals are marine mammals. Common species include Arctic fox, wolverine, mink, and stoat. Bear, sea otter, and spotted seal are abundant here, as are in some places, fox, wolf, Eurasian lynx, and American mink. Colonies of Kamchatka marmot are situated on coastal terraces (Sivuchy Bay and coastal shores). Ground squirrels and pikas usually live near volcanoes. The population of big horn sheep along the coast is very important for the survival of the species. Unfortunately, as in many other areas of Kamchatka, there are hardly any reindeer.  

A diversity of marine mammals occupies the reserve. Whale species include gray whale, minke whale, blue whale, sei and finwhales. Killer whales and harbor porpoise are also present. Pinnipeds haul out on rocky headlands, riffles,and islands, including hundreds of sea lions (before 1985–86 there were up to 2,500–3,000,but in 1988 their numbers decreased). The sea otter, or kalan, is one of the most significant species in the reserve and the impetus for its creation. There was a time when this species was hunted nearly to extinction. Today, sea otters gather in large numbers along the southern coast of the Kamchatka Peninsula. There are about 1,500–2,000 sea otters within the sanctuary. The animals are part of the Northern Kuril population.