River bottom may be culprit
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October 26, 2013 |
The eggs of endangered Kootenai River white
sturgeon are less likely to hatch on some of the
surfaces that have been made more common by
human, or anthropogenic, changes on the river, a
new U.S. Geological Survey report has found.
The white sturgeon, once common in much of North
America, is a very large, slow-to-mature fish
that has evolved little from its late Cretaceous
ancestors 175 million years ago.
It has great cultural significance for the
Kootenai Tribe of Idaho and many other Northwest
tribes.
White sturgeon was harvested in many places for
caviar, and dams and other development have
altered its habitat in ways whose implications
are still being studied.
White sturgeon in Idaho’s and Montana’s Kootenai
River basin were listed as endangered in 1994,
and poor recruitment (the number of a species’
young to survive to maturity) in other West
Coast populations is a concern.
"Sturgeons are imperiled across the globe. Our
scientists are committed to working with
partners, including tribes, to address sturgeon
issues across the region," said Jill Rolland,
director of the USGS Western Fisheries Research
Center.
In the report, prepared in cooperation with the
Kootenai Tribe of Idaho, USGS research fishery
biologist Mike Parsley and biological science
technician Eric Kofoot examined hatch success in
the laboratory on various surfaces, such as
clean rocks, algae-covered rocks and sand, that
sturgeon eggs settle and adhere to in the wild
while they develop into larvae.
The scientists found sand to be a poor surface,
because the developing sturgeon embryos failed
to attach to it. River rocks covered in algae
yielded poor results, in part because they were
more hospitable to fungus that threatens
sturgeon embryos, while waterlogged wood and
clean rocks performed well.
The report notes that sand substrates, or
surfaces, now dominate the highly altered
Kootenai River in areas currently used by
spawning sturgeon, and that dam operation for
flood management and hydropower during the
spawning season have largely eliminated spring
scouring flows that typically would clean rocks
of algae and other growth.
Finally, the report raises several
possibilities, based on the findings, for
maximizing white sturgeon recruitment, including
substrate-type recommendations for
spawning-habitat restoration and the
incorporation of scouring flows to clean
spawning substrate prior to the spawning season.
"This is another piece in the puzzle of
understanding why some white sturgeon
populations in highly altered river systems
succeed and others don’t," Parsley said.
The publication, "Hatch Success of White
Sturgeon Embryos Incubated on Various
Substrates," USGS Report Series 2013-5180, by
Michael J. Parsley and Eric Kofoot, is available
online at
http://pubs.usgs.gov/sir/2013/5180. |
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