[env-trinity] CBB: Declining Steelhead: Study Says Conditions Early In Marine Life Phase Strong Contributors To Survival

[Sari Sommarstrom]

Any similar studies off the California coast?

 

The Columbia Basin Bulletin: Weekly Fish and Wildlife News

www.cbbulletin.com

July 14, 2017       Issue No. 837

 

Declining Steelhead: Study Says Conditions Early In Marine Life Phase Strong
Contributors To Survival

 

West Coast steelhead runs are declining and a new study pegs much of the
problem to poor survival of smolts early after entry into the ocean.

 

After entering the ocean, steelhead smolts head out over the continental
shelf from wherever they enter the ocean - British Columbia, Puget Sound,
the coastal areas of Oregon and Washington and from the Columbia River - and
then turn north to the Gulf of Alaska where the fish all mix before
returning to their natal spawning grounds. While in the Gulf of Alaska
steelhead remain more dispersed and school less than salmon while in the
ocean.

 

Although steelhead are known for this long-distance migration in the ocean,
it appears that conditions close to where young steelhead enter the ocean
from freshwater contributes more to their survival than conditions in the
open ocean.

 

Steelhead abundance in the Pacific Northwest has declined since the 1980s
and marine survival rates have likely contributed to that decline,
especially for lower Columbia River and Puget Sound steelhead.

 

"Our paper suggests that conditions early in the marine life phase of
steelhead trout, shortly after they enter salt water, are strong
contributors to their total marine survival patterns," said Dr. Neala
Kendall, research scientist with the Washington Department of Fish and
Wildlife, and lead researcher of the study.

 

"This suggests that the steelhead are either compromised when they enter
marine waters, such as from contaminants or parasites, and/or that they are
more likely to be eaten by a predator in recent years than in the 1980s,"
she continued.

 

As for predators - harbor seals, harbor porpoises, birds and fish-eating
fish - it could also be that there is less other food, such as the forage
fish herring and anchovies, in Puget Sound for these predators to eat, so
they target steelhead smolts more, Kendall said.

 

"Therefore, management actions that reduce contaminants and parasites and
promote and protect forage fishes, such as reducing shoreline armoring,
could be helpful," she said. "We are currently in the process of conducting
additional work that will shed more light on what factors are related to
this increased mortality."

 

Other species of salmonid, including juveniles, are also being targeted by
predators in Puget Sound, British Columbia and in the Columbia River.

 

The study's researchers analyzed steelhead adult abundance from 35 coastal
British Columbia and Washington populations, along with smolt to adult
return information from 48 populations from Washington, Oregon and the Keogh
River in B.C. It found that more than 80 percent of the populations studied
had declined since the 1980s.

 

They also found that smolt survival declines were seen in three of four
populations since the 1990s, including the Columbia River, Puget Sound and
the Keogh River.

 

"We were able to compile data from multiple reports and databases to
document survival in the ocean of Oregon, Washington, and B.C. steelhead
trout and show that these trends paralleled declines in adult abundance and
also differ among populations originating from different areas," Kendall
said. "We believe this is the first time these data have been brought
together in a single study."

 

The information shows differences in populations originating from different
areas, she added. 

 

"In particular, Lower Columbia River and Puget Sound steelhead marine
survival rates have declined since the early 1980s. These declines likely
contributed to these fishes' low abundance and listing on the Endangered
Species Act. Coastal Oregon and Washington steelhead marine survival rates
have varied over time but have not declined in the same way that Lower
Columbia River and Puget Sound steelhead have. Coastal steelhead are not
listed on the Endangered Species Act."

 

The study, "Declining patterns of Pacific Northwest steelhead trout
(Oncorhynchus mykiss) adult abundance and smolt survival in the ocean," was
published online June 26, 2017, in the Canadian Journal of Fisheries and
Aquatic Sciences "
(http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2016-0486#.WWTmQIjyvI
U). Kendall's co-authors are Gary Marston, natural resource scientist, and
Matt Klungle, research scientist, both with WDFW.

 

Populations with particularly concerning declines were those in the Lower
Columbia River and in Puget Sound. Ocean survival of juvenile steelhead
populations in Puget Sound in the 2000s declined by 77 percent on average
compared to the 1980s, the study says. Survival averaged 3.1 percent in the
1980s but dropped to 0.7 percent in the 2000s.

 

Similar trends were found for adult abundance. Adults in Puget Sound in the
2000s declined by 53 percent on average compared to the 1980s.

 

The declines in juvenile survival "likely contributed to these fishes' low
abundance," Kendall said. Abundances are so low that Puget Sound steelhead
were listed for protection under the ESA in 2007. Steelhead populations in
B.C. included in the study also have declined in abundance and ocean
survival since the 1980s. Declines in survival of juvenile steelhead in
ocean environments were not as drastic for populations along the coasts of
Washington and Oregon which are not listed under the ESA.

 

Survival and abundance trends, like those generated in this study, can
enhance current tools being used to predict changes in steelhead
populations, according to a news release published in Phys.Org
(https://phys.org/news/2017-06-steelhead-trout-population-declines-linked.ht
ml)

 

To best conserve steelhead in the Northwest, Kendall said "stakeholders and
concerned citizens want to better understand why these populations have been
struggling and how marine survival has contributed. With this information,
policymakers and managers can have different expectations about Puget Sound
and Lower Columbia steelhead [compared to] fish on the coast due to their
different marine survival patterns."

 

She sees this study as providing further support for ongoing efforts by
natural resource agencies and NGOs to improve steelhead survival and protect
the habitats these juvenile trout use upon arriving in the ocean. 

 

The research is part of the Salish Sea Marine Survival Project, a US-Canada
collaboration of more than 60 organizations conducting research to
understand why salmon and steelhead are dying in the Salish Sea.

 

Also See: 

 

-- CBB, July 7, 2017, "Study: Harbor Seals Target Salmon Juveniles Of
Conservation Concern In Salish Sea," http://www.cbbulletin.com/439218.aspx

 

-- CBB, June 23, 2017, "Puget Sound Study: Pinniped Predation On Juvenile
Salmon Making Salmon Recovery More Difficult,"
http://www.cbbulletin.com/439144.aspx

 

-- CBB, June 23, 2017, "Pinniped Report: Sea Lions Leave Bonneville Dam With
Likely High Salmon Predation Rate In Their Wake,"
http://www.cbbulletin.com/439149.aspx

 

 

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