2024 Trout Survey Report

The latest Trout Survey on the Snake River was completed in September 2024. This was accomplished by the Nebraska Game & Parks Commision. Thad Huneman supervised the effort with 7 NGPC members as well as 6 SFSC members. The effort included new shocking equipment in a single pass survey. The 2024 NGPC report is attached (pdf format) with a few discussion points.

SURVEY METHOD
It is important that members understand the sampling process. The NGPC uses a one pass survey, while Colorado and Wyoming generally use a multi-pass technique with marked captures and recaptures or a floating net capture for assessment at the end of shocking. The latter method is preferred when trying to compare fisheries in other regions, but the NGPC uses the one pass survey across all fisheries in order to be consistent. However, the 2024 effort had new equipment (new barge tote with 3 retractable leads) and sufficient volunteers for dip netting and fish measurements. Having been at each survey over the last 10 years, I believe the 2024 effort was in the 50-80% capture range and far more efficient than any surveys prior. We were able to simultaneously shock the entire width of the river, provide better dip netting and capture. Less credence should be given to prior surveys in this reach and more consideration should be given to the 2024 survey in determining relative abundance.

BARRELS SITE
At the Barrels, 501 Rainbow and Brown trout were captured over 175 meters. Using the Catch per Unit Effort (CPUE), this equates to roughly 4,600 trout per mile. With such a short sampling length, one should be cautious in equating the relative abundance over a larger reach such as a mile. This is because 1) the reach shocked may be an anomaly and 2) the remaining “mile” of stream morphology/habitat may be significantly different. But for those of you that have walked the river there are great lengths of river with very similar productive habitat and it is reasonable to use the CPUE recorded. Adjusting for stream variances and capture efficiency(%) the total per mile could be 5,000 or perhaps only 4,000 trout per mile. The important information here for members is that the stream below the Falls would qualify as a High Tier fishery and would meet the criteria for a High Productivity trout stream in Colorado or Wyoming. Think “Blue Ribbon” or “Gold Medal” fishery.

ABOVE THE FALLS
The site sampled above the Falls ranged from the old bridge pilings to just underneath the new bridge. Here, 24 rainbow trout were captured, an estimated 177 trout per mile. In 2021, the Gauging Station reach was surveyed and had 68 Rainbow trout with an estimated 724 trout per mile. I am confident the Stout reach would be higher as it has had 18 years of restoration targeting improved spawning, young of year, over summer, and adult habitat. This just shows some of the variance in the stream morphology and spawning sites making it difficult to estimate relative abundance over 4 miles. In 2016, this same 2024 reach was surveyed and had only 5 or 6 trout captured. Since then the reach has had indirect improvement with cattle removed, improved bank stability and vegetation, narrowing of the stream, less fines and more gravels. Above the Falls is consistent with a moderately productive fishery, but with a high trophy trout potential.

DIFFERENT FISHERIES
As many members have recognized, there are essentially two different fisheries, one above the Falls and one below. Each has different attributes and members are cautioned about comparisons as they are more like apple and oranges. Differences include stream morphology, spawning site abundance, habitat, thermal regime and diet.

HEALTH OF FISHERY
Overall, the fishery and stream are healthy. We saw no evidence of disease or malnutrition. Water quality is excellent!

DIVERSITY
A side note about stream diversity if I may. In the survey above the Falls, we captured a few Johnny Darter species, the first time we had found something other than trout, White Sucker or Longnose Dace. Prior to 1963, the Snake River had greater native species such as Johnny Darter, White Sucker, Brassy Minnow, Bigmouth Shiner, Pearl Dace, Finescale Dace, Northern Redbelly and Longnose Dace, and perhaps a few more I could not substantiate. As you can see, many are gone since 1963 when a dam went up, the river received rotenone treatment to eradicate rough fish species and trout were aggressively stocked. Certainly, not a pristine river, but there may be some of these species, hybrids or other in isolated stretches.