Saimaa Ringed Seal is one of the few freshwater seals to live. Due to the melting of ice sheets and as the land uplift broke the connection to the Baltic Sea, the Saimaa Ringed Seal become isolated in Finland’s largest lake close to 8000 years ago. Over time these seals have adapted to life in murky waters of Lake Saimaa, their brains and eyes grew larger than those of its relatives. The Saimaa Ringed Seal is endemic to Lake Saimaa in Finland and are not found anywhere else in the world. Making them one of rarest species of seal in the world.
The Saimaa Ringed Seal spends majority of its life under the murky waters of Lake Saimaa. They can also sleep underwater. As they spend majority of their life underwater, they have adapted to life in the water. A seal can navigate the maze of island and islets with the help of its sight and whiskers, which it uses as a sensory organ. The seal’s hypodermic fat layer acts as an excellent insulator in the water and their large hind flipper enable quick moves when foraging.
An adult seal can eat up to 1000 kgs of fish a year. The amount of body fat present in the seals varies heavily on the season. With the seals at their fattest in early winters before the lake freezes and at its thinnest in early summer, after breeding season.
Sadly, these seals face many threats which have dropped their population to 400 individuals. Due to hunting, environmental toxins, changes in the water level during the breeding season, and by-catch mortality, the seal population collapsed towards the end of the 20th century. Some of the threats have been defeated, and the Saimaa Ringed Seal population has been growing slowly in this century. However, there is still plenty to do to secure the future of the seal.
- Hunting: The seal was hunted, and a bounty was paid for killing them until the 1940s. Hunting them was forbidden and the Saimaa Ringed Seal was protected by a decree in 1955.
- Environmental toxins: The high mercury concentrations in Lake Saimaa in the 1960s and 1970s, in particular, had a detrimental effect on seal reproduction.
- Water level fluctuation: The great variation in the water level of Lake Saimaa used to destroy the winter lairs of the seals, until in 1991, an agreement of regulation of the outflow was signed to stabilize the water level fluctuation during the ice covered season.
- By catch mortality: The adoption of nylon gill nets in the 1960s has been disastrous for the seal population.
But today these seals face new and different threats.
- Climate change: A snowy winter is essential for the survival of seal pups.
- Small population: If seals are too closely related, this weakens the gene pool.
- Disturbance during the breeding season: Disturbing the seals during the breeding season may result in the death of the pup.
- Building on shorelines: The increase of year-round living on the shores of Lake Saimaa decreases the amount of areas suitable for seals as breeding and resting sites.
- By-catch mortality: Pups, in particular, still get entangled in gill nets and drown in fish traps which have a wide opening.
Article written by Ishaan Shrimali and art by Nandini Saluja
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