According to a preliminary report released this week a total of 5,010 fall chinook salmon redds – supposed egg-filled nests that will produce a new generation -- were observed in the lower Snake River and its tributaries this past fall, which is the second highest count since inception of intensive surveys in 1988.
The 2011 overall redd count was 620 redds fewer than the record count set in 2010.
The low redd count is 54 in 1991, according to a record kept by the Idaho Power Company. That’s the year before Snake River fall chinook salmon were listed as threatened under the Endangered Species Act because of declining populations. Much of the species historic habitat was cut off with the construction of dams in southeast Idaho and along the Idaho-Oregon border (IPC’s Hells Canyon Complex).
The annual redd surveys are conducted by biologists from the Idaho Power Company, Nez Perce Tribe, U.S. Fish and Wildlife Service and the Washington Department of Fish and Wildlife. It was the 24th year that intensive aerial surveys have been conducted in the Snake River and most of its major tributaries above Lower Granite Dam and the 20th year for ground surveys in tributaries downstream of the southeast Washington dam. The totals come from aerial, ground and underwater video counts.
Before 2010, the previous overall high count had been 1,910 in 2009. The number of returning spawners has been growing since that 1992 listing because of a variety of remedial actions and, at times, help from Mother Nature. Measures have been taken to improve habitat conditions for a species that spawns, for the most part, in mainstem rivers, and to ease their passage up and down through the Columbia-Snake hydro system. Lower Granite is the eighth dam the fish must past on their way to spawning grounds and hatcheries.
The 2011 adult fall chinook count at Lower Granite’s fish ladders was 28,922, second highest on a record dating back to when counts began in 1975. The highest was 41,815 in 2010; third highest now is 16,628 in 2008.
The return includes naturally produced fish from the Snake, Tucannon, Grande Ronde, Imnaha, Salmon and Clearwater rivers and tributaries, as well as four artificial propagation programs: the Lyons Ferry Hatchery, Fall Chinook Acclimation Ponds Program in the Clearwater and lower Snake, the Nez Perce Tribal Hatchery, and Oxbow Hatchery fall-run chinook hatchery programs.
The return would seem to have benefited considerably from a fall chinook “supplementation” project led by the Nez Perce Tribe that began in 1996. The program involves bringing hatchery produced juvenile fish to acclimation sites on the lower Snake and Clearwater rivers for their final rearing before release. The sites are located near major natural spawning areas in hope that the fish would return as adults to spawn.
The overall return over Lower Granite also includes hatchery fish too that are outplanted each year by IPC below Hells Canyon Dam.
IPC and USFWS staff during aerial, ground and underwater video counts observed a total of 2,837 redds this year in the mainstem Snake River.
The aerial surveys attempted to cover the river corridor between Asotin, Wash., and the Hells Canyon Dam (approximately 100 river miles). Intensive deep-water spawning searches were conducted throughout the main river corridor, using remote underwater video cameras in areas too deep to be viewed from the air.
Spawning was estimated to have begun in mid-October, appeared to peak in early November (925 new redds observed on Nov. 7) and was determined to be complete by early December.
Since 2002, the mean number of redds occurring in the Snake River (including deep water counts) has been 1,763, ranging between 1,025 and 2,944, according to the Feb. 7 preliminary report. The lowest redd count for the Snake River, since intensive surveys began, was 46 redds in 1991, while the highest count was 2,944 redds in 2010.
A new technique for counting, and estimating shallow redds, was tested during the fall of 2011 with IPC biologists using a small remote controlled aerial drone (hexacopter), equipped with a video camera to enumerate redds at index sites, according to the report. A set of 17 index sites were chosen and were flown over once per week throughout the spawning season.
Previous year’s data from those sites indicate that a relationship can be developed and used to estimate total shallow Snake River redds based on the total number of redds observed at those sites. Preliminary assessment of the video data clearly shows redds (as well as fish) at each site.
A final count, comparison with biologists “eyes in the skies”, and a total estimate of shallow redds, based on the video, data will be forthcoming,” according to the preliminary report.
“However, based on what was observed during the season, the use of the hexacopter for ultimate data collection was a clear success, and it is recommended that this type of technology be adapted for future use, in lieu of helicopter surveys, based on safety and cost,” the report says.
For a short video showing the hexacopter in use, follow this link: http://videos.oregonlive.com/oregonian/2011/12/snake_river_salmon_survey_empl.html
During aerial and ground surveys, Nez Perce staff observed a total of 1,621 redds in central Idaho’s Clearwater River subbasin. Redd searches covered the entire Clearwater River from Potlatch Mill in Lewiston, Idaho, to the forks of the South Fork and Middle Fork Clearwater rivers (approximately 71 miles), lower Potlatch River (5 miles), about one half mile of the lower North Fork Clearwater River below Dworshak Dam, the entire Middle Fork Clearwater River (22 miles), lower South Fork Clearwater River (14 miles) and lower Selway River (19 miles).
Surveys conducted on the South Fork Clearwater, Middle Fork Clearwater and Selway (which ultimately feeds the South Fork) produced a count of 12, 16 and 3 redds, respectively. That’s the highest redd count in all three upper Clearwater tributaries since surveys began in the South Fork during 1992 and in the Middle Fork and Selway during 1994.
“Every year, we continue to observe redds in new spawning locations throughout the Clearwater River Subbasin and this year was no exception,” the preliminary report says.
“Since 2002, the mean number of redds occurring in the Clearwater River Subbasin has been 916, ranging between 487 and 1,924 (average includes a redd estimate of 514 redds in 2006, because of turbid conditions and missed surveys after peak spawning). The lowest redd count for the Clearwater River Subbasin, since intensive surveys began was four redds in both 1990 and 1991, while the highest count was 1,924 redds in 2010.”
A total of three aerial surveys conducted by NPT staff on northeast Oregon’s Grande Ronde River resulted in a total of 154 redds observed. The lowest redd count for the Grande Ronde River and its tributaries since intensive surveys began was zero in 1989 and 1991, while the highest count was 263 in 2010.
Final results will be provided in annual reports to Bonneville Power Administration. Past reports can be found at www.bpa.gov.