Is there any limitation on foreign nationals travelling by passenger boat Omsk – Salekhard or Salekhard – Antipayuta?

Severflot in summer and autumn operates passenger boats on the Yenisey and Ob rivers, from Omsk in the south to Antipayuta in the north. On this river-forum post, someones writes that Обязательно привезти копию первой страницы паспорта и копию свидетельства о рождении (emphasis mine) (Google translation: "Be sure to bring a copy of the first page of the passport and a copy of the birth certificate"). I would have a па́спорт (passport) in any case, but the need for a свидетельство о рождении (birth certificate) makes me wonder if they might limit foreign nationals. There are certainly places with travel restrictions for foreign or even Russian nationals. On the other hand, the eastern Siberian Lenaturflot advertises in English that Also voyage Yakutsk – Tiksi is popular among tourists from Russia and foreign countries. Usually such tourists come to Yakutia without taking a package tour. As a foreigner, can I simply buy a ticket on one of those river boats or might some be for Russian nationals only?