Are Sea Lions Endangered? Conservation Status and Threats

Sea lions comprise a total of six extant species. Three sea lion species are endangered by the International Union for Conservation of Nature (IUCN), and one is endangered under the United States' Endangered Species Act (ESA). This article discusses the status and threats of these different species and what is being done to protect the most threatened populations.

Endangered Sea Lion Species

The genetically isolated Australian sea lion is believed to number 6,500 mature individuals in a decreasing global population throughout Western and South Australia and is endangered by the IUCN and on the state level within its existing range.

Similarly, the Galapagos sea lion jumped from vulnerable to endangered by the IUCN in 2008 and is fully protected under Ecuadorian law after being hunted to near extinction for their fur in the early 20th century. The species declined by almost 24% following the last significant El Niño event in 2015.

Also in 2015, the IUCN added the New Zealand sea lion to the endangered list, citing a 98% probability of extinction in the species' largest general population within just five generations. At the time, there were just over 3,000 individuals left in total. 

On the other hand, the Steller sea lion is considered "not threatened" by the IUCN but endangered under the ESA and protected under the Marine Mammal Protection Act. Why? According to the IUCN, a large uptick in the Loughlin Steller sea lion subpopulation between 1985 and 2015 compensated for losses elsewhere. 

Threats

Sea lion species are vulnerable to pollution, climate change, bycatch, and diseases introduced by other species. Complications from gillnet fishing represent a considerably significant threat to both Australian and New Zealand sea lions, while Galapagos sea lions are more susceptible to climate change, disease, and pollution.  

Pollution

Like all coastal marine animals, sea lions are threatened by ocean pollution. Since they're top predators, toxins from pollution or harmful algae blooms that affect smaller prey species can build up in sea lions, leading to neurological changes, behavioral changes, or even death.

Plastic waste at sea and shore frequently entangles sea lions. At the same time, oil spills have been shown to represent a significant danger to Steller sea lions. One study found that Steller sea lions were the fourth most vulnerable species to oil spills in British Columbia, following sea otters and several species of killer whale.

In 2021, scientists made headlines when they finally uncovered the cause of a mysterious cancer that had been killing California sea lions for 40 years. Unfortunately, the culprit was toxic chemicals from industrial trash, pesticides, and oil refinery waste.

Climate Change

All sea lion species are vulnerable to the effects of climate change on ocean conditions. Especially as warming temperatures result in weakened currents, it can impact the abundance of fish prey in sea lion habitats. Scientists who studied a three-decades-long sustained ocean warming event in the Gulf of California connected it to a 65% decline in the sea lion population between 1991 and 2019.

Studies at San Miguel Island off the coast of Santa Barbara have also found that sea lion pup weights decrease during El Niño events, disrupting spawning times and locations of sardine and anchovy populations. In the years leading up to 2016, animal rescue centers saw large numbers of stranded, underweight sea lion pups. A study by NOAA Fisheries linked to a decline in high-calorie sardine and anchovy populations (rich in fat that's vital to early sea lion pup development). Nursing females were being forced to feed on prey like market squid and rockfish, which have far less fat and calories, and therefore struggled to meet their pups' nutritional needs.

Bycatch

Although the greatest historical threat to sea lions—intentional culling and hunting—has mostly ended, some animals are still killed accidentally in net fisheries. Commercial fishing may also alter the distribution and abundance of sea lion prey, affecting the reproduction success and overall health of the species. When sea lions become entangled in fishing gear like traps or gillnets, they may drag and swim for long distances, becoming fatigued, severely injured, or compromised in their feeding ability.

Getting caught in various fishing nets is a major cause of death for the endangered Australian sea lion, who are attracted to the bait material in rock lobster pots. Young pups especially are at risk of drowning when they cannot escape the pots.

Disease

The highly concentrated nature common among sea lion subpopulations makes them more vulnerable to disease outbreaks. In 1998, 2002, and 2003 epizootic outbreaks at the Auckland Islands led to a 50%, 33%, and 21% early pup mortality in New Zealand sea lions, respectively. The cause of the outbreak during the latter years was discovered to be linked to severe respiratory disease caused by Klebsiella pneumoniae bacterium.

In 2001, during a viral outbreak of canine distemper in the settlement on San Cristobal, Santa Cruz, and Isabela islands, it was actually recommended that all dogs on the islands be vaccinated to reduce the risk of transmission to Galapagos sea lions. 

What We Can Do

Like seals, sea lions belong to a group of marine mammals known as pinnipeds who live primarily in the ocean but are able to come on land for long periods of time thanks to their adapted "foot-like" flippers. Because of this, they're not the easiest to count, identify, and monitor. Scientists in Glacier Bay, Alaska, are using a combination of counts from aerial photographic surveys and in-water sightings from vessel surveys to help bridge the gap.  

When it comes to endangered sea lion species, countries like Australia have specific recovery plans. In 2018, the Western Australia government established a series of sea lion protection zones around known breeding colonies in which fishing with gillnets is strictly prohibited. In South Australia, a decade-long program organized by the Australian Marine Conservation Society and Humane Society International aimed at preventing gillnet use near sea lion colonies has helped reduce fishing net deaths by 98% in those areas.

Studies have shown that establishing more marine reserves across sea lion habitats can increase prey fish diversity, biomass, and even overall population numbers. Community marine reserves could also help improve the resilience of marine mammals to certain climate-driven effects, as well as marine ecosystem health, directly benefiting sea lions and fishermen alike.