Chaunsky District (; Chukchi: , Čaan rajon) is an administrative and municipal district (raion), one of the six in Chukotka Autonomous Okrug, Russia. It is located on the northern shore of the autonomous okrug and borders with Iultinsky District in the northeast, Anadyrsky District in the southeast, and with Bilibinsky District in the south and west. The area of the district is . Its administrative center is the town of Pevek. Population: The population of Pevek accounts for 80.8% of the district's total population.
Chaunsky District is flat compared to other districts in the autonomous okrug. The land within the current boundaries was first discovered by non-indigenous people in the 18th century, and now the indigenous people of the district are a minority as ethnic Russians came to the area following a growth in mining.
Geography
The district is centered around the Chaunskaya Bay, on the shores of which Pevek, the administrative center of the district, is situated. The district's territory also includes Ayon Island, found at the entrance to the Chaunskaya Bay. There is an eponymous settlement on the island.
The district's territory stretches for from north to south and for from east to west. Cape Shelagsky is its northernmost point. Chaunsky District is significantly flatter than Bilibinsky District located to the west and contains large areas devoted to reindeer pasture.
Approximately long, the Chaun River, which flows into Chaunskaya Bay, is the longest river in the whole autonomous okrug.
There are a number of wetland areas of significance within the district. The most westerly of these is situated on the Kyttyk Peninsula and the mouth of the Rauchua River. This area is dominated by the Lower Rauchua delta and the alluvial plains of the Kyttyk Peninsula, from which Ayon Island is separated by the Maly Chaunsky Strait. The peninsula is almost completely covered in a complex system of lakes, ranging in size from small saline pools lying on a recently exposed marine terrace 1 to 2 m above sea level, near the coast, to lakes up to 1 km wide and 12 m deep on high level surfaces 10–15 m above sea level. In addition, the peninsula is scored by a number of rivers, the Eyukuul, Koz'mina, Rakvezan and Emykkyvian among the most significant.
The Ust-Chaun area of the district also contains significant wetlands at the south end of Chaunskaya Bay, consisting mainly of an alluvial plain approximately 100 km wide and 60 km north to south. The wetlands at Ust-Chaun are similar in structure to those at the Rauchua / Kyttyk wetland, consisting of a landscape almost entirely filled with small lakes, those nearest Chaunskaya Bay are the smallest and shallowest (less than 70 cm deep) and those on more elevated ground being deeper at 1.5–3 m deep The Ust-Chaun region serves a fishing centre for the inhabitants of Rytkuchi, although this has lost its importance in recent years as stocks of Char have diminished, as a result of overfishing both for sale to the local Sovkhoz and as bait for trapping foxes.
Flora
There are approximately 200 different species of plant within the Rauchua / Kyttyk wetland area comprising a variety of steppe, boreal and arctic species, a number of which occur at the eastern limit of their natural habitat. In the Ust-Chaun area, there are even more recorded plant species, at 252., including a number of rare species.
Fauna
Humpback and chum salmon enter the lower reaches of the Rauchua. Several species of whitefish, grayling and smelt also live in the river or in the many surrounding lakes. Sticklebacks also live in the lakes along with Arctic char, although the community of char is infested with Acanthocephala. Similar fish exist in the Ust-Chaun region, and in addition to fish, the wetland is also home to the Siberian newt, which lives in the shrub-covered tundra near the delta.
The Rauchua / Kyttyk wetland area is considered to be the easternmost extent of so-called "Kolyma fauna", such as the Terek sandpiper, brown shrike and scarlet rosefinch. The most common bird species in the Rauchua / Kyttyk wetland are the yellow-billed, black-throated and Pacific divers. One of the main reasons for the importance of the Rauchua / Kyttyk is the breeding population (figures as of 1994) of Bewick's swan (approximately 300 birds), the Pacific eider (approximately 3,000 birds) and the spectacled eider (approximately 2,000 birds). Spectacled and Pacific eider as well as black-throated and Pacific divers are also found in the Ust-Chaun region, though the Pacific eider is much more common on the Kyttyl Peninsula and near Apapelgino.