California Sea Lion Mystery
Sea lions are one of the top predators in the Kelp Forest and its surrounding ecosystems using their front flippers to propel them through the water and their sensitive whiskers known as vibrissae to catch squid, octopi, molluscs, crustaceans and fish. They have adapted to slow their heart rates and stint blood flow to non essential body parts when diving to reach depths of 1,760ft and can remain under water for up to 20min. Under of the Marine Mammal protection act it is no longer legal for humans to hunt sea lions which were once hunted heavily for their furs and blubber leaving only a few natural predators such as sharks and Orca Whales. California Sea Lions are social animals often grouping up on shores or in the water, a group of sea lions in the water is known as a “raft”. The easiest way to tell a sea lion from their relatives the seals is that sea lions have small external ears flaps where as the seals do not. Sea lions also have a rotating pelvic joint that along with their strong front flippers allow them to walk on land more effectively than seals. Sea lions can often be seen thermo-regulating by laying on their sides in the water with one of their flippers sticking out of the water catching the sun’s rays. By pushing blood into capillaries near the surface of the exposed flipper it absorbs the heat from the sun heating up the rest of the sea lion as it continues along its path through the circulatory system. Sea lion hunters used to think that this thermo-regulating made their fins look like the handle of an old ceramic or glass jug and so named it “Jug Handling”, to others it looks like the sea lion is waving “hi” to any who pass by.
Sea lions are always a pretty common site around Howland’s Landing whether they’re chasing a school of fish through the cove or swimming by our Kayakers their aquatic acrobatics are always a crowd pleaser. Over the last few seasons at CELP we have noticed a dramatic increase in the number of sea lions around Catalina Island. Where we used to see rafts of 3-6 sea lions thermo-regulating or swimming along the coast the number of individuals in the rafts has increased into the dozens of late with a couple rafts passing by containing 50-75 sea lions.
This year has seen an unbelievable increase in the amount of sea lions stranded on main land beaches too most of which are small sea lion pups. Where last year Los Angeles County had 36 sea lions reported stranded on its beaches the beginning of this year has already seen over 400 stranded sea lions. Counties up and down the coast of California have seen similar increases in their stranded sea lions. There have been instances in the past involving large numbers of sea lions getting sick from domoic acid poisoning. Domoic acid is a toxin produced by small phytoplankton. Under normal circumstances domoic acid is in such low concentrations that it isn’t harmful to marine life. When there is plenty of sun and an increase in the nutrient levels in the water though whether from natural occurrences or pollution the algae can bloom in exponential numbers, the red coloring of the algae has earned these blooms their name of “red tides”. As domoic acid climbs the food chain it builds in concentration through a process called biomagnifications. Large amounts of domoic acid in sea lions affects the brain causing them to become lethargic, disoriented, and to have seizures that sometimes result in death. Veterinarians and scientists still aren’t quite sure what is causing the number of stranded sea lions to increase so drastically but with marine mammal rescue centers already filling up there are hoping to find a reason and solution as quick as possible. If you’d like to learn more here are some links to other articles relating to the increase in stranded sea lion.
The Marine Mammal Center takes in malnourished California sea lions to assist Southern California rehabilitation facilities
‘Unusual mortality event’ is declared for the California sea lion
Residents help out sea lion stranded on Newport Beach boardwalk
Starving Baby Sea Lions Flood Southern California Shores
Starving sea lion pups fill Calif. rescue centers