The abundance of resources allow the population of seals to increase over the years until the population reaches carrying capacity due to a limited number of resources and the population plateaus.
As other populations run out of resources such as fish, they will immigrate into other seal populations that have an abundance of fish. Therefor, increasing the size of the population.
As seals move out of the population in search of better resources such as more fish, the size of the population will decrease as seals move on to other populations.
As more seals are born, the size of the population increases, which limits the amount of resources available for that population.
As seals die, the size of the seal population decreases, therefor, increasing the number of resources available to that population.
Two density dependent factors include disease and competition. If one of the seals were to become sick with a life threatening disease, it is very likely that the entire population of seals could become sick and eventually die because they all live so close together, therefor limiting the size of the population. With a large population of seals, they will likely have to fight for food which could end up killing part of the population as the stronger seals win the food, therefor, limiting the size of the population.
Two density independent factors include storms and habitat disruption. If a massive storm or tornado were to hit the habitat of the seals, many of the seals would die, therefor limiting the size of the population. If the habitat were to be disrupted by other animals or even humans, most likely many seals would die, therefor limiting the size of the population.