“Friendly faces” turned up earlier this year than last and for only the second time in the past four years off the Northwest coast, a “dramatic shift” that might be good news for salmon and other fish stocks.
Federal biologists say offshore samples they’ve been collecting in recent months have been “full” of three different species of coldwater copepods, and they report “healthy” numbers of adult krill are also being seen.
“These are all good indications that the zooplankton community is transitioning back to a more ‘normal’ state,” writes Samantha Zeman on the Northwest Fisheries Science Center’s always interesting Newportal blog.
It’s been all out of whack since The Blob began to affect the northeast Pacific beginning in 2013, with the “hangover” from the humongous pool of too-warm saltwater continuing into last year.
“These coldwater copepods are lipid-rich and represent a productive food chain for higher trophic levels,” explains Zeman.
Their arrival also marks a “biological spring transition” that is key for coho and Chinook, with the earlier they’re seen translating to higher survival for silver salmon.
“This is especially exciting because in recent years (2015 and 2016) we never saw the copepod community transition from a warm winter community to a cold summer upwelling community, and in 2017 the transition occurred very late in the season,” Zeman writes.
An NWFSC chart showing transition dates since 1970 simply says “Never” for both 2015 and 2016.
In the former year, the annual June survey of juvenile salmon at sea was marked by emaciated coho.
Sampling also began turning up pyrosomes, a tubular organism that feeds on plankton and is generally found in more tropical waters, but the numbers of which exploded last year, fouling fishing gear from Oregon all the way to Alaska. A new study suggests they may be adapting to our cooler ocean and could become a permanent part of the biome.
NWFSC’s chart also shows that coldwater copepods have otherwise been present for as long as 263 days in 2007 and 252 in 2009 to as few as 29 in 1983 and 57 in 2005.
The spring transition has begun as early as March 4 in 2008 and around the first day of spring in 1970, ’71, 2007 and ’09, to as late as July 21 in 1983 and June 28 in 2017.
Meanwhile, we’re waiting to learn more about results from this June’s juvenile salmon sampling.
Last year’s turned up some of the lowest numbers of juvenile Chinook and coho seen in the past two decades, which federal biologists could translate into “lean times” this year and next for some rivers’ stocks, including the Columbia.
But with the earlier arrival of copepods, hopefully this year’s fish are faring better.