the est across the Yana-Indigirka Lowland, part of the greater East Siberian Lowland. Further north, where the terrain becomes completely flat, the Indigirka divides into branches from the mouth, forming a wide delta. Its waters end up in the Kolyma Bay, East Siberian Sea. Gusinaya Bay is located to the northwest of the mouths of the Indigirka. The Indigirka freezes up in October and stays under the ice until May–June. Tributaries The main tributaries of the Indigirka are, from source to mouth: Khastakh (Tuora-Yuryakh) (left) Taryn-Yuryakh (right) Kuydusun (left) Kyuente (left) Elgi (left) Nera (right) Chibagalakh (left) Moma (right) Selennyakh (left) Druzhina (left) Badyarikha (right) Uyandina (left) Shangina (right) Bolshaya Ercha (right) Allaikha (left) Byoryolyokh (left, into Russko-Ustyinskaya) Shandrin (right, into Kolymskaya) Ports, settlements and economy Main ports on the river are: Khonuu Druzhina Chokurdakh Tabor There is a gold prospecting industry in the Indigirka basin. Ust-Nera, a gold-mining center, is the largest settlement on the river. The Indigirka teems with a variety of fishes. Among the most valuable are several whitefish species, such as vendace, chir, muksun, inconnu (nelma), omul, etc. Mouths The Indigirka forms a large delta, consisting of a number of streams (each one being labeled on Russian maps as a photo ka (river arm)) and islands. About before reaching the East Siberian Sea (), the river splits into two major northeast-flowing streams. The left (westernmost) arm is known as the Russko-Ustyinskaya Protoka; the right arm, the Srednyaya Protoka (Russian for the "Middle Arm"). Further downstream, the third major arm, the Kolymskaya Protoka splits off the Srednyaya Protoka as its right (eastern) distributary, thus justifying the "middle" moniker for the Srednyaya Protoka. While Srednyaya Protoka means the "Middle Arm", the names of the main western and eastern arms indicate their relative location as well. The Kolymskaya Protoka, or Kolymskoye Ustye is the arm one located on the eastern side, i.e. the "Kolyma side" of the delta (the arm closest to the Kolyma, the eastern neighbor of the Indigirka). The Russko-Ustyinskaya Protoka, apparently known earlier as simply Russkoye Ustye is the arm one located on the western side, i.e. the "Russian side" of the delta (meaning, the side closest to the (European) Russia). These days the name of the Russko-Ustyinskaya Protoka appears as if it were formed from the name of the old Russian village Russkoye Ustye situated there, but originally the opposite is likely to have been