The great drawbacks to navigation are (I) the long winter frost, during which the river and its tributaries become sledge routes,.the ice lasting from 90 to 160 days; the average date of break-up of ice is April II at Tver, the 25th at Kostroma, the 16th at Kazan, the 7th at Stalingrad and March 17 at Astrakhan (2) the shal lowness of the river during late summer and the frequent forma tion of islands and their dissolution during flood time.
The network of shallow and still limans or "cut offs" in the delta of the Volga and the shallow waters of the northern Caspian, freshened as these are by the water of the Volga, the Ural, the Kura and the Terek, is exceedingly favour able to the breeding of fish, and as a whole constitutes one of the most productive fishing grounds in the world. As soon as the ice breaks up in the delta innumerable shoals of roach (Leuciscus rutilus) and trout (Luciotrutta leucichthys) rush up the river. They are followed by the great sturgeon (Acipenser huso), the pike, the bream and the pike perch (Leucioperca sandra). Later on appears the Caspian herring (Clupea caspia), which formerly was neglected, but has now become more important than stur geon; the sturgeon A. stellatus and "wels" (Silurus glanis) follow, and finally the sturgeon Acipenser giildenstadta, so much valued for its caviare. In search of a gravelly spawning-ground the sturgeon go up the river as far as Sarepta (250 m.). The lamprey, now extensively pickled, the sterlet (A. ruthenus), the tench, the gudgeon and other fluvial species also appear in immense num bers. Destructive exploitation at spawning time has much dimin ished the yield of the Volga fisheries, and the discharge of oil from steamers has also had an adverse effect.
The Volga was probably known to the early Greeks, though it is not mentioned previous to Ptolemy. According to him, the Rha is a tributary of an interior sea, formed from the confluence of two great rivers, the sources of which are separated by 20 degrees of longitude. The Arab geographers throw little light on the condition of the Volga during the great migrations of the 3rd century, or subsequently under the invasion of the Huns, the growth of the Khazar empire in the southern steppes and of that of Bulgaria on the middle Volga. In the 9th century the Volga basin was occupied by Finnish tribes in the north and by Khazars and various Turkish races in the south. The Slays, driven perhaps to the west, had only the Volkhov and the Dnieper, while the (Mohammedan) Bulgarian empire, at the confluence of the Volga with the Kama, was so powerful that for some time it was an open question whether Islam or Christianity would gain the upper hand, and Islam is strong in Kazan to-day. But, while the
Russians were driven from the Black Sea by the Khazars, and later on by a tide of Ugrian migration from the north-east, a stream of Slays moved slowly towards the north-east, down the upper Oka, into the borderland between the Finnish and Turkish regions. After two centuries of struggle the Russians succeeded in colonizing the fertile valleys of the Oka basin ; in the 12th century they built a series of fortified towns on the Oka and Klyazma; and finally they reached the mouth of the Oka, there founding (in 1222) a new Novgorod—the Novgorod of the Lowlands, now Nizhniy Novgorod. The great lacustrine depression of the middle Volga was thus reached; and when the Mongol invasion of 1239-42 came, it encountered in the Oka basin a dense agricultural popu lation with many fortified and wealthy towns—a population which the Mongols found they could conquer, but were unable to drive before them as they had done so many of the Turkish tribes. This invasion checked, but did not stop, the advance of the Rus sians down the Volga. Two centuries elapsed before the Russians covered the 30o m. which separate the mouths of the Oka and the Kama and took possession of Kazan.
With the capture of Kazan (1552) the Russians found the lower Volga open to their boats, and eight years afterwards they were masters of the mouth of the river at Astrakhan. Two cen turies more elapsed before the Russians secured a free passage to the Black Sea and became masters of the Sea of Azov and the Crimea; the Volga, however, was their route.
's Geographical and Statistical Dic tionary (5 vols., St. Petersburg, 1863-85) contains a full bibliography of the Volga and tributaries. See also V. Ragozin's Volga (3 vols., St. Petersburg, 1880-81, with atlas; in Russian) ; N. Bogolyubov, The Volga from Tver to Astrakhan (Russian, 1876) ; H. Roskoschny, Die Wolga and ihre Zufiiisse (Leipzig, 1887, vol. i.), history, ethnography, hydrography and biography, with rich bibliographical information; N. Boguslayskiy, The Volga as a Means of Communication (Russian, 1887) , with detailed profile and maps ; Peretyatkovich, Volga region in the 15th and r6th Centuries (1877) ; and Lender, Die Wolga (1889). The Don and Volga Basins (192o), Foreign Office Historical Handbook No. 53 (English).