Southern Resident Orcas in Decline

Southern Orcas in steady decline 

The west coast of Canada and the US is host to distinct family groups of Orcas, also known as killer whales, one of which is known as the southern pod. The black and white whales are a popular tourist attraction in the Juan de Fuca and Victoria, BC, area.

The University of Washington has conducted a multiyear study of the southern pod, trying to determine which deleterious environmental stimuli have the most impact on the group. They looked at boat traffic, toxins in the water and abundance of food. The study continued for seven years, from 2007 to 2014.

The conclusion, published this year, named the lack of the Orcas’ preferred food as the number one factor in the decline of this family group. The resident Orcas depend heavily on salmon to maintain their health. The southern population depends on salmon for 95% of its food and the majority of that is the variety known as Chinook Salmon.

The researchers looked at returns to both the Fraser and Columbia Rivers and found a correlation between low returns of Chinooks and a high pregnancy failure rate. Over the period of research, the failure rate was 69%.

The picture for these animals is not good. The salmon returns continue to decline and that trend is expected to continue.

"As it stands now, the orca numbers just keep declining with no signs of recovery," said Wasser. "We're losing a valuable resource here." Sam Wasser, researcher

The Chinook salmon(ONcorhynchus tshawytscha) goes by many names: King, Quinnat, Spring, Tyee.

Further Reading:

Science Daily

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