Also known as the Saddleback seal, or the Greenland seal, the harp seal spends most of its life at sea.
Thankfully it is a fast breeder, and is therefore capable of bouncing back fast.
They have a global population of around 7.6 million, and there are 2 recognized subsepcies. They migrate long distances (as much as several thousand miles, but unfortunately all 3 populations are hunted by various countries.
In the past, that hunting quota has had horrific effects on population size, with it being as low as 1 million and as high as 9 million at different times in the last 150 years. These days the quota is worked out scientifically, which has stopped human caused seesaw of the population size.