Wind offers reprieve to struggling, dying fish in Hood Canal dead zone

Wind offers reprieve to struggling, dying fish in Hood Canal dead zone

By Craig Welch, Seattle Times
29 Sep 2010

Normally bottom-dwelling quillback rockfish (top) and a few yellowtail rockfish hover near the surface of Hood Canal, while a stressed sunflower star (left) spreads its webbing; both scenes attributed to a lack of oxygen.
Normally bottom-dwelling quillback rockfish (top) and a few yellowtail rockfish hover near the surface of Hood Canal, while a stressed sunflower star (left) spreads its webbing; both scenes attributed to a lack of oxygen.

 


Wolf eels lay sluggish on rocks, their gills pumping in and out as if panting. Deep-water rockfish and shiner perch congregated in massive schools at the surface. An octopus died and turned a sickly white.

Early this week, divers working with scientists in Hood Canal once again saw thousands of fish struggling — and sometimes failing — to stay alive in the canal’s upper reaches, one of the few places in the water column with enough oxygen for them to survive.

Tuesday morning things looked worse: Surface waters, too, had become lethal.

Then a late-Tuesday wind shift brought fresher water and more oxygen from the north. For the second time in as many weeks, that pattern appeared to forestall a feared death sentence for marine creatures in southern Hood Canal.

But scientists worry that the danger is a long way from over. "I’m really surprised — and very glad — but I’m also mindful that we need to see what it looks like in the morning," said Jan Newton, a University of Washington oceanographer. "It could be that we’ve once again dodged a bullet, but we don’t really know what tomorrow

[Wednesday] will bring."

Scientists have been warning all month that oxygen conditions in Hood Canal are the worst they’ve seen in years and could at any moment lead to the suffocation of tens of thousands of fish.

Twice last week, hundreds of creatures washed up dead on the canal’s shores, but oxygen levels improved before things grew worse.

On Monday poor conditions returned with a vengeance, and researchers were bracing themselves for wholesale marine death.

But late Tuesday, Tony Parra, a marine biologist with the Washington Department of Fish and Wildlife, and other divers went back underwater again, where things had slowly begun to improve.

Fish still clustered near the surface, straining to capitalize on a slight increase in oxygen brought about by a shift in the wind.

A single white spotted greenling appeared to have suffocated, and wolf eels and other fish were still panting. But, for the moment, the worst seemed to be over.

For more than a decade, natural conditions and increasing pollution have led to recurring bouts of low-oxygen in Hood Canal. That oxygen-depletion results in a floating dead zone that has at times killed thousands of fish, most notably in 2003 and 2006.

The problem comes at the end of summer after algae blooms, nourished by nitrogen from sewage and other runoff, die and decompose in the southern part of the canal. That uses up oxygen throughout much of the water column. That "hypoxic" water is eventually flushed from the canal.

But last year much of that dangerous water stayed in the canal and has now been compounded by another summer of algae growth. This year that low-oxygen zone sometimes stretches vertically through more than 150 feet of water, and has pushed most of the fish to the surface.

Through the night Monday, strong south winds pushed the surface waters north, allowing poorly oxygenated water from below to take its place, leaving nowhere for the fish to go.

"I don’t know how anything can survive right now," diver Janna Nichols said Tuesday. She’s a volunteer who shot underwater photographs and video Monday and returned Tuesday to take a second look. Monday, "I saw an octopus die right in front of me. I saw it breathe, and then it stopped, just like that. And it’s definitely worse today."

By late afternoon Tuesday, the wind had shifted to the north, which brought fresher water back into the canal.

Measurements taken from research gauges late in the afternoon showed oxygen levels in and around Hoodsport had increased from one milliliter per liter to about two milliliters. Anything below five is stressful for fish respiration; below two is considered lethal.

Scientists remain sufficiently concerned that they planned to be out working through the night Tuesday, monitoring beaches with flashlights to keep tabs on any fish mortality.

The concern is that Wednesday’s 3:15 a.m. minus tide, the biggest in 24 hours, could strand the seriously weakened fish near shore.

"We may see lots of fish dying overnight, or maybe no fish die — hopefully that’s the case," Parra said.

Either way, "chances are pretty good that I won’t be getting much sleep." 

Craig Welch: 206-464-2093 or cwelch@seattletimes.com

http://seattletimes.nwsource.com/html/localnews/2013019126_hoodcanal29m.html
 

2017-01-17T09:22:10+00:00 October 7th, 2010|News|Comments Off on Wind offers reprieve to struggling, dying fish in Hood Canal dead zone