 In 1840 he became an employee of the Russian-American Company and soon became the manager of the Okhotsk port.He deduced that the port was inconvenient for trade, as it was too far from the Lena River basin and advocated transfer of the Company port to Ayan.During his exploration Zavoyko discovered the estuary of the Amur River (the exploration was later continued by Gennady Nevelskoy, who proved that the Strait of Tartary was not a gulf, but indeed a strait, connected to Amur's estuary by Nevelskoy Strait).