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Canada Ocean Report:
2008 Coldest Water In 50 Years

by Bill Rudolph
NW Fishletter, June 19, 2009

Like most of the waters off the West Coast, the Pacific Ocean off British Columbia was super salmon-friendly last year, according to a new report by Canada's Department of Fish and Oceans. In fact, these waters were the coldest of the past 50 years.

The report said phytoplankton and zooplankton concentrations were the highest over the latest decade of collecting data across the Gulf of Alaska. "The cause is yet uncertain, but injection of iron by winds or currents is suspected (iron is a limiting factor in this region), along with higher levels of nitrate and silicate in spring.

Oxygen levels remained high near the surface in early 2009, but generally declined in deep waters along the continental slope over the past few decades. "A sudden decline in bottom-water oxygen concentration in 2008 on the continental shelf was likely due to denser water with naturally low oxygen levels moving up onto the shelf in this year due to anomalous winds and currents. This oxygen drop may have been a factor in the movement of some groundfish species to shallower depths in 2008."

The report said despite relatively cool marine conditions the past two years, many BC salmon populations remained at low levels, due partly to warmer ocean water between 2003 and 2005. Sockeye numbers stayed low coastwide, "...with one notable exception being Okanagan sockeye that returned in record numbers in 2008."

Fraser sockeye populations continued to suffer from high pre-spawning mortality from high water temperatures in tributaries.

Southern BC coho populations remained at depressed levels, but northern populations improved.

"For chinook, the situation is somewhat reversed," said the report. "Northern populations continue to decline while the status of southern chinook is highly variable."

With improving ocean conditions, BC sockeye and coho that went to sea in 2008 are expected to return at average to above-average levels.

More than 10 million sockeye are predicted to return to the Fraser River this year. Less than 2 million returned last year.

Bill Rudolph
Canada Ocean Report: 2008 Coldest Water In 50 Years
NW Fishletter, June 19, 2009

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