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Siberian least cisco (Coregonus sardinella)

Superior mouth and delicate toothless jaws make this fish look like a herring, but the real herring does not have an adipose fin. The scales of this fish are large, silver and easily falling. It is not difficult to distinguish the least cisco from other whitefishes. The semi-anadromous fish often have dark spots on the dorsal and adipose fins. Least cisco can use diverse ecological niches, and can populate different types of waters.

Least cisco dwell in many drainages of the Arctic Ocean, including the lakes close to the Bering Strait, in the Anadyr River, and on the Bering Sea coast of Chukotka, in Northern Alaska and Canada.

The semi-anadromous form feeds in brackish lagoons and coastal areas, entering rivers in the fall to spawn and winter. The resident, lake-river form spends summers in lakes and slow channels and comes into the main river in the fall. Both anadromous and resident fish spawn on sand or gravel bottoms in medium current in October.

There are also purely lake-resident populations of least cisco, whose entire life cycle takes place in stagnant water. The mature specimens of the semi-anadromous form most often weigh from 100 to 300 grams, sometimes up to 600 grams. The lake-resident fish reach an average size of 100–200 g. In some lakes of Chukotka there are 1-kg “giants.” In the same lake you might find dwarf ciscos, which are mature at a mere 20–30 grams.

In some waters, these two forms of the Siberian least cisco live together. The food of the species is very diverse. It can eat small crustaceans (zooplankton), near-bottom and bottom invertebrates (amphipods, insects, and mollusks), fish fry and insects falling into the water.

Ilya Sherbovich