[env-trinity] CBB: Changing central Pacific El Niños reduce stability of North American salmon survival rates

[Sari Sommarstrom]

http://www.cbbulletin.com/434695.aspx

http://www.pnas.org/content/early/2015/07/28/1503190112.abstract?sid=142826d
f-a34f-4b88-88aa-c2561d84dfcc

 


El Nino Weather Patterns May Be Cause Of Coho, Chinook Ocean Survival
Becoming Similar 
Posted on Friday, August 07, 2015 (PST) 


The biodiversity of two Northern Pacific salmon species may be at risk due
to changes in ocean conditions at the equator, reports a study by the
University of California, Davis. 

 

In the study published in the journal Proceedings of the National Academy of
Sciences  <http://www.pnas.org/> http://www.pnas.org/ Aug. 3, researchers
tracked the survival of chinook and coho salmon from hatcheries in North
America between 1980 and 2006.

 

Before the 1990s, ocean survival rates of chinook and coho salmon varied
separately from each other. However, the researchers were surprised to find
that survival rates of the two species have since become increasingly
similar. 

 

"Two species that historically have had different responses and seem to be
very different in their coastal-wide patterns now appear to be more
synchronized," said lead author Patrick Kilduff, a postdoctoral scholar
under Louis Botsford in the UC Davis Department of Wildlife, Fish and
Conservation Biology at the time of the study. "When salmon populations are
synchronized, it's either good for everyone or bad for everyone--similar to
the stock market." 

 

>From an economic perspective, it means that when catch of one species is
low, catch of the other also will tend to be low.

 

This synchronous response to ocean conditions represents a loss in
biological diversity that cannot be addressed directly by freshwater
management actions, the study said. 

 

It's not yet well understood what is causing the increasing similarity, but
the researchers said it could reflect a change in coastal ocean food-web
linkages or perhaps a change in the salmon species themselves. 

 

Historically, many Pacific salmon species were thought to be influenced by
the Pacific Decadal Oscillation (PDO), an El Nino-associated eastern Pacific
warming pattern. As the nature of El Niños has changed, another ocean
indicator, the North Pacific Gyre Oscillation (NPGO) has grown increasingly
important, but its impact on salmon was not well-understood. 

 

This new study found that coho and chinook salmon survival rates along the
West Coast are more strongly connected to the NPGO than to the PDO. 

 

"Changes in equatorial conditions lead to more of the large-scale Pacific
Ocean variability being explained by North Pacific Gyre Oscillation, and
it's influencing the survival of salmon from Vancouver Island south to
California," Kilduff said.

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www2.dcn.org/pipermail/env-trinity/attachments/20150807/099951b4/attachment.html>