LAGUNA BEACH ( — Thirteen likely pregnant female sea lions were rescued last week in waters off the coast of Orange County that exhibited symptoms of domoic acid poisoning.

An ocean algae bloom creates the neurological toxin. The sick sea lions were found in waters from Seal Beach to San Onofre State Beach, according to the Orange County Register.

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The Pacific Marine Mammal Center in Laguna Beach confirmed Tuesday evening that seven of the 13 sea lions have passed away.

Officials say the sea lions’ plight could signal that the marine environment continues to remain out of balance.

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The newspaper reports a lack of food sources available to lactating mothers close to Channel Islands sea lion breeding grounds led to mass strandings starting in 2013.

The sea lions are exposed to the toxins when they eat surface fish such as sardines and anchovies that consume the algae. Animal care experts say pregnant females are especially vulnerable because they are eating as many fish as they can while pregnant.

The Pacific Marine Mammal Center has begun accepting donations to help treat sick sea lions by starting an Amazon “wish list” page for anyone wishing to help with the effort.

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)