Known/Unknown

Dead Steller Sea Lion On Beach [1]

Decline:
There are currently many different possible threats and interactions with humans that cause the decline of the Steller sea lion populations. What is known is that threats do exist, but what we do not know is which threats and how many of them are having a major impact on the species.

Steller Sea Lion Strangled By Net [2]

What We Do Know:
Steller sea lions face life-threatening danger as a species as well as individuals. While swimming, they are in danger of being hit by the bottom of boats and ships, the propeller being especially dangerous. Pollutants and contaminants are a problem for all species and can cause early deaths and infertility. Sea lions require the shoreline as habitat which is being lost in many areas. This habitat degradation limits the population size. As shown to the left, getting caught in fishing nets frequently occurs and can kill or maim sea lions for life.

Estimated Numbers Of Steller Sea Lions In Alaska From 1956 To 2000 [3]

What We Don't Know:
Since the 1970's the Western Population of Steller sea lions has decreased drastically. In the 1990's, the dwindling population became a national concern. Intense research has been conducted on the topic with no decisive conclusions as to why the decline occurred. Possible contributing causes are:

• Juvenile Deaths: The population will not be able to increase as much without adults to reproduce. 

• Predation: Killer whales pose a constant threat of extinction if other issues become too prominent.

• Contaminants: Sea Lions live in extreme environments and their bodies must regulate hormones efficiently. As pollution and human presence increases, contaminants may further impact Steller sea lion health.

• Disease: As with any animal species, particularly mammals, Steller sea lions are susceptible to diseases, even epidemics.

• Malnutrition: Steller sea lions require a large variety of food to maintain a healthy nutrition. If even one food source were to be removed, the entire population could suffer from malnutrition. 

• Infertility: Many different factors could easily impact reproduction. This is vital to maintain because without the reproducation, the population's future is at risk. 

• Lack of Food: With fishermen to compete against for fish, finding food is increasingly difficult for the Steller sea lion. 

It is imperative that we determine what caused the tragic decline of the Western Population of Steller sea lions. As you can see in the graph shown above, a decline of similar magnitude could completely wipe out either the Western or Eastern Populations.