Life Science – Why are Sick Seals Lying on the Beach?


Numerous recent news stories have aired about sick seals. I recently almost tripped over one while walking at Redondo Beach. That seal looked very weak and was barely moving. I alerted a person working at the beach. He told me they had seen numerous seals come on shore every day. He said he has seen kids playing and jumping over the sick seals.

What is making seals sick?

Planktonic algae, also known as phytoplankton, can produce toxins during certain conditions, leading to harmful algal blooms (HABs). Specific species of algae produce these toxins and can harm marine life, including seals, if they consume contaminated prey or directly come into contact with the toxins.

Currently, beaches are seeing many marine mammals that are affected by domoic acid, this toxin  overstimulates nerve cells in the brain, leading to a condition known as amnesic shellfish poisoning (ASP).

Seals suffering from ASP may experience bewilderment, difficulties navigating, and general disorientation in their surroundings. Domoic acid can cause seizures by involuntary muscular contractions and aberrant behavior. Seals may exhibit strange behaviors like as lethargy, restlessness, and repeated movements.

Memory loss is one of the most serious side effects of domoic acid. Seals may suffer from memory loss, making it difficult for them to find food or navigate their environments.

What can we do to help?

Well, first, keep away from the sick or dead seal. If you see a dead or sick animal on the beach, alerting a beach worker or lifeguard is a good idea. They will know the next steps to take. If still alive, the seal may end up at a Marine Mammal Care Center like the one in San Pedro.

To assist in sea lion and seal rescue efforts, individuals can email [email protected], providing details, including the stranded sea lion’s location and a photo, if possible. Additionally, supporting the cause can be done by visiting the Marine Mammal Care Center’s website and donating.

Is there a danger to surfers or people in the water?

Most of the time, seals get sick because of the food chain. Fish eat the poison phytoplankton, which then gets eaten by the seals. Sharks eat seals, so it is conceivable that a large number of weak or sick seals in an area could increase the number of sharks. Changes in seal behavior or distribution caused by illness can indirectly impact shark behavior and mobility. For example, if sick seals are concentrated in certain areas, sharks may be drawn to such areas, but this does not always imply a long-term increase in shark numbers.

Can people get sick from Domoic Acid?

Domoic acid primarily accumulates in shellfish, such as mussels, clams, and scallops, when these organisms feed on the toxic algae responsible for its production. Consequently, consuming contaminated shellfish can lead to a condition known as amnesic shellfish poisoning (ASP) in humans. Eating infected seafood, rather than direct exposure to ocean water during recreational activities, is the key concern regarding domoic acid and human health. Domoic acid is normally not present in high enough concentrations in the water itself to cause health issues. Following seafood safety guidelines and staying up to date on local advisories can help reduce the dangers of domoic acid poisoning.


In conclusion, I don’t believe that sick seals are a great danger to surfers or people on the beach, as long as efforts are made to stay away from them. I’m cautious, so I would not swim in the ocean, knowing that many marine mammals were getting sick, and I would think twice about eating a lot of fish from an area experiencing increased marine mammal illnesses. If you see a sick or dead marine mammal on the beach, please report it to the proper city department.