Plastic in pinnipeds, part of a very big problem

September 5, 2018

By Dr. Lauren Palmer, Veterinarian at Marine Mammal Care Center Los Angeles

Over the last 26 years the Marine Mammal Care Center, located in San Pedro, has admitted almost 8,000 stranded marine mammals. These are primarily California sea lions, northern elephant seals and harbor seals from Los Angeles County beaches, stretching from Zuma Beach all the way down to Seal Beach, about 70 miles of coastline. Most of these animals strand due to natural causes, but on average 6% of animals strand each year in Los Angeles County as a result of human interaction. The most common types of human interaction include entanglement, hooking, ingestion of gear or garbage, vessel trauma, gunshot, stabbing, mutilation, or harassment.

The vast majority of human interaction related strandings we treated were due to entanglement or ingestion of fishing line, hooks, and sinkers associated with recreational and commercial fishing. Rarely, in previous years, did we find evidence of ingestion of trash or plastic in pinnipeds.

In 2017 this changed in a notable way.   In 2017 there were seven cases of pinnipeds that died as a result of garbage ingestion. In the previous 24 years, the average number of cases of garbage ingestion was 0-2 each year for a total of 18.  In 2017 plastic bags, small pieces of broken plastic, sponge like substances, and even a small piece of cloth, were found in the stomachs of deceased sea lions. One harbor seal died with a piece of cloth stuck in the intestine.  Compared to historical averages seven animals dying with evidence of garbage ingestion is quite high and probably underestimates the true number as there are likely to be many more animals that did not make it to shore alive or were not examined.

This sea lion passed 13 plastic bags and survived. Most aren’t so lucky.

The stomach of a sea lion will hold a large quantity of fish, but fish is digested in the stomach into a thin pasty substance that can pass through the narrow pylorus from the stomach into the intestine. The pylorus is about the diameter of a finger, depending on the age and size of the animal. In all cases in 2017 this passageway from the stomach to the intestine was blocked by garbage. In one animal we found 6 plastic bags, in another, just a small piece of plastic wedged perfectly to create a blockage.

Plastic is ubiquitous in our environment and it is taking its toll. But it is not the only problem. Garbage of all types exerts its lethal effect on marine life in the form of entanglements and ingestion that result in long term suffering ultimately leading to starvation and death.

What can we do to keep plastic and trash out of the ocean?  Here are just a few examples:

  • Try biodegradable fishing line and see if it can work for you. Traditional fishing line may take hundreds of years to break down, but the development of new biodegradable line will break down in 1 year. Don’t abandon fishing line or nets of any amount in the ocean- bring it back to shore to dispose of properly.
  • Think about celebrating without leaving or releasing balloons and strings or similar products for years to come. Balloons released into the air always come down somewhere as trash and if near the ocean, pose a risk to marine life. Metallic coated balloons won’t decompose for years. Memories of the party should last longer than the balloon!
  • Reuse and recycle plastic bottles and bags, or better yet, don’t use them at all.
  • Get your groups to actively participate in beach cleanups.

Unique organizations, like AltaSea, are working to bring businesses, non-profits and educators together to have a major impact on our ocean stewardship responsibilities.   Our sea lion hospital sees the results of ignoring this problem for many, many years and is honored to share our bit of the puzzle with your readers.

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