Reef Check News


Stranded: Southern California Sea Lion Pups


2013-04-29

By Brianne Billups, Reef Check California SoCal Volunteer Coordinator

A rare event is currently taking place along the Southern California coast. Since January of this year, more than 1,300 malnourished sea lion pups have come ashore in the area spanning from Santa Barbara to San Diego. Marine mammal rescue centers have been overwhelmed by the extraordinarily high numbers of sea lions coming into their facilities. This has led the National Oceanographic and Atmospheric Administration (NOAA) to declare an "unusual mortality event".

The stranded sea lion pups were born last summer and it is abnormal to see them on coastal beaches now, considering they should be with their mothers at the Channel Islands. Sea lions born during that time typically don’t wean until April or May. In general, they are turning up alive but severely emaciated, some weighing less than 20 pounds when they should be well over 50 pounds at this point in their development, marine officials say.

Due to the fact that almost all of the stranded pups are extremely underweight, scientists believe the mass stranding is occurring since they are not getting enough food. Environmental conditions in the area are being studied for clues as to why the pups are starving. Scientists are focusing their investigation on factors such as changes in algae growth, wind patterns and sea surface temperature, which have led to sea lion stranding epidemics during years past.

The leading hypothesis is that particular sea conditions are cutting the sea lion pups' main food supply of anchovies and sardines. While adult sea lions and other marine mammals are more adaptable and can change their feeding habits in the face of a shortage, pups are more limited in how far they can travel for food and what they can eat. As part of their investigation, scientists are also testing blood and tissue samples for bacterial, viral and other infectious agents as well as traces of radioactivity.

While the exact cause of the high numbers of sea lion strandings is still to be determined, scientists are working diligently to pinpoint a reason. In the meantime, rescue centers are working at their maximum capacity to release rehabilitated pups back into the wild.