Given the thermal regime of this river, March 1st is upon us and so is the Rainbow spawn. The water coming out of the dam is slightly warmer than the thermal regime of the upper Snake River during the winter months. Around the 1st week of March, the temperature will hit 40-41 degrees Fahrenheit getting those big hen trout stirred up. We have been able to correlate the thermal regime (by HOBO temp probes) with onsite observation of Redds being made. A Redd is the term for the nests that fish scoop out in the gravels substrate, mainly by the sweeping actions of the tail. They prefer shallow areas with good gravel substrate and downwelling of water through the tail end of the gravel. So, you may see the nests at the tail of a pool just before the next riffle. Or, on the inside of a bend with the current coming off the substrate at an angle directed toward the middle ( deeper) section of river.
I have mapped out Redds in the river over the last 5-6 years. Below the Falls, the Redds are numerous, often coalescing with each other and too many to count. Above the Falls, they can be identified from the dam to the Little Sandy. However, they are in far less numbers and unevenly distributed. But, likely adequate in numbers along with the Catch & Release Only rules as well as habitat enhancement. In 2018, I counted over 25+ Redds in the Big Sandy stretch, mainly upstream of what I call the Step Falls, where one of the saw mills used to be. You will find 1-4 Redds at the tail of the Big Sandy pool near the edges, as well. A few Redds were 16-25 square feet in size, evidence of big hens, likely >21-22 inches. At a time when folks were complaining about no big fish above, this type of survey information was decidedly comforting. More importantly, it helps the SRPG BOD recognize these important areas of diversity and protect them for the future.
To that point, members are Reminded to Wade & Fish appropriately in shallow waters from March to May, especially in areas like the Big Sandy. I have include a sat map from 2018 to give an idea of the area on the Big Sandy.
Tight Lines & Careful Wading this Spring,
pat