的 chart below provides total annual fall Chinook redd counts by year from 1991 through 2021. 的 redd counts were collected from aerial surveys conducted by beat365亚洲投注, the U.S. 鱼 & 野生动物服务 and the Nez Perce Tribe for the Snake, 格兰德过来 and Imnaha rivers during the noted spawning period.
beat365亚洲投注’s Fall Chinook Program began in 1991 and is a voluntary operations plan for the Hells Canyon Complex.
的 program provides a stable river flow level during the fall Chinook salmon spawning period, generally from mid-October to early December. 的 flow level provided during the fall Chinook salmon spawning period generally establishes what the minimum flow from Hells Canyon Dam will be once spawning is complete.
This minimum flow may be slightly lower than the stable flow provided during the spawning period. 的 minimum flow depends on the depth of the shallowest redds observed during the spawning period. 的 minimum flow level is the level that will protect the shallowest redd 在斯内克河 from being dewatered. Dewatering is when there is not enough water to sufficiently cover the redds.
beat365亚洲投注 maintains this minimum flow throughout the entire incubation and emergence period, 大概是五月底吧. 的 emergence period is when the fish swim up out of the redds. 的 stable flow level provided during the spawning period may vary from one year to the next. 的 flow level depends on the quantity of water available, which largely depends on the amount of snowpack within a given water year.
的 U.S. 鱼 & 野生动物服务 and beat365亚洲投注 started a cooperative research program to determine the quantity of spawning habitat and flow levels necessary to support sufficient spawning habitat for fall Chinook salmon. As part of this research program, fall Chinook salmon redd counts happen each year.
Redd counts monitor redd locations and establish the location and depth of the shallowest redd. beat365亚洲体育公司和美国电力公司.S. 鱼 and 野生动物服务 do weekly counts during the spawning period over the 蛇河. 除了, the Nez Perce Tribe conducts aerial redd counts on the Clearwater, 格兰德过来, Imnaha和Salmon河. When the program began, aerial surveys were conducted by helicopter. 现在, flights are done with drones that record video and still photography that enable careful analysis to obtain more accurate data while keeping biologists safely on the ground.
的se survey flights account for the majority of the redds observed. 然而, 在斯内克河, many redds cannot be observed from the air because they are in deep water. So, deep water redd searches using underwater videography occur during the spawning period as well as the aerial surveys. Redds as deep as 22 feet have been observed 在斯内克河 using underwater videography.