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.
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