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Slow Growth of Southern Sea Otters

Aug 22, 2012 08:08 AM EDT

Sea Otter population has significantly increased in the West Coast but is facing a slow recovery amid facing death risks due to sharks, according to a new survey conducted by the U.S. Geological Survey (USGS).

The survey report released Tuesday revealed that the southern sea otters have increased 1.5 percent per year since 2010. The population of the sea otters currently stands at 2,792 compared to 2,711 in 2010.  

Although the otter population has increased since 2010, researchers pointed out that the overall population growth has not been fast enough and is still a matter of concern. According to the USGS report, a record number of 335 otters were found stranded and an increasing number of sea otters are said to be facing deaths by bite wounds caused by white sharks.  

"We saw an increase in death due to white shark 'tasting' bites," Melissa Miller, the necropsy veterinarian at the CDFG Marine Wildlife Veterinary Care and Research Center, said in a statement from the USGS.  

The International Union for Conservation of Nature (IUCN) has placed sea otters' status as 'endangered'. According to IUCN, the world-wide population of sea otters has declined to nearly 50 percent over the last 30 years.

The number of sea otters, which were once popularly used in the commercial fur trade, decreased to 2,000 in 1911. Although the population growth of the species has increased since 1980s due to efforts taken by various countries, the pattern in their population growth has dwindled owing to various factors.

In the United States, the sea otters are listed as threatened species due to their slow growth and mortality rates. Besides shark bites, experts also found other factors such as algal toxins, boat strikes and infectious diseases that have contributed to the otter deaths.  

"We are working closely with our collaborators to understand what could be driving this new trend. The usual causes of deaths were also evident: harmful algal toxins, parasites and infectious diseases, mating trauma, emaciation, bacterial infections, heart disease and boat strikes round out the list," Miller said.

While nothing much can be done with respect to the natural factors contributing to the sea otter deaths, the creatures need to expand to the new areas that can provide sustained life in order to cope with non-natural factors, said Lilian Carswell from the U.S. Fish and Wildlife Service.

According to USGS, the 'threatened' status of sea otters can be removed if their population exceeds 3,090 for three consecutive years.

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