Orcas, or killer whales, which spend at least part of each year in the Puget Sound, off the Washington state coast, are still at risk, despite years of study and human intervention.

A new report by the National Oceanic and Atmospheric Administration asserts the recovery of the so-called Southern Resident population, which comprises 80 whales, continues to be hampered by pollution, vessel noise and lack of available food.

Since 2003, NOAA scientists have collected data on the orcas, ranging from fecal and biopsy samples to satellite-tracked locations and behavioral observations to provide as comprehensive an understanding as possible of the population's health and impact of recovery efforts.

"This new report provides insights into the threats facing Southern Resident killer whales, as well as new information as to why these whales are not recovering as quickly as hoped," NOAA Fisheries marine biologist Lynne Barre said in an agency news release. "NOAA Fisheries and our partners can use the findings and information contained in this report, as well as future research, and apply it directly to our overall efforts to help these animals recover as we work to maintain healthy oceans for current and future generations."

According to the study, NOAA has over the years implemented several strategies in hopes of addressing the primary threats to the whales' well-being -- first and foremost by imposing restrictions on how close vessels can get to the whales.

The agency has also collaborated and partnered with organizations responsible for the removal of contaminants in Puget Sound, researched and promoted the development of orca food resources and adopting killer establish whale-specific emergency response plans in the case of oil spills.

The key actions identified by the study include the following focus issues:

  • Chinook salmon make up a majority of the whales' diet, particularly in the summer. Many runs of Chinook are endangered or threatened, potentially limiting the food source.
  • Pollutants cause disease and reproduction problems in marine mammals. Southern Resident killer whales are among the most contaminated marine mammals in our oceans. Pollution and contaminant levels are particularly high in young whales.
  • When vessels are present, the whales hunt less, travel more and modify their vocalizations.
  • Future research is needed to answer questions like whether the new vessel regulations are successful in reducing impacts, how large an impact do high contaminant loads have on whale health and reproduction, and how large a population can today's ecosystem support.

Researchers believe the Southern Resident killer whale population once numbered at least 140 animals. But, in the 1960s and '70s, nearly 50 animals were removed from the population and placed into theme parks.

The practice of capturing live orcas for display was eventually stopped in 1976, but only about 71 of the Southern Resident group remained.

The Southern Resident whales rebounded in the '80s, peaking at 98 animals in 1995.

The population began to decline again in the early 2000s, and in 2005 was granted endangered species status through the federal Endangered Species Act

The population was counted at 82 individual whales last year.