Ladoga seal Ladoga seal The Ladoga ringed seal (; Pusa hispida ladogensis), is a freshwater subspecies of the ringed seal ("Pusa hispida") which are found entirely in Lake Ladoga in northwestern Russia. The subspecies evolved during the last ice age, about 11,000 years ago. As the glaciers retreated and water levels changed, the Baltic ringed seal (including Ladoga seals) was trapped in freshwater lakes and separated from the Arctic ringed seal. It is related to the even smaller population of Saimaa ringed seals in Lake Saimaa, a lake that flows into Ladoga through the Vuoksi River. The adult Ladoga seal grows to
Lake Ladoga due to uplift of the Baltic Shield in the north. It has been hypothesized, but not proven, that waters of the Litorina Sea, the next brackish-water stage of the Baltic, occasionally invaded Ladoga between 7,000 and 5,000 BP. Around 5,000 BP the waters of the Saimaa Lake penetrated Salpausselkä and formed a new outlet, River Vuoksi, entering Lake Ladoga in the northwestern corner and raising its level by 1–2 m. The River Neva originated when the Ladoga waters at last broke through the threshold at Porogi into the lower portions of Izhora River, then a tributary of the Gulf of