North Platte River Wyoming
Here are some facts the Wyoming Game and Fish Department released in the Casper Region Angler Newspaper in 2012 about the North Platte River from Robertson Rd to Glenrock which is 42 miles downstream of Grey Reef Dam.
We conducted a population estimate on the North Platte below Robertson Road in October. The trout population stood at 960 fish per mile with 1,070 pounds of trout per mile. Rainbow trout comprise 94% of the overall trout population with brown trout representing 6%. Rainbow trout average 14 inches in this reach with individuals as large as 6 pounds captured. The brown trout through this reach are slightly larger on average but as with the rest of the North Platte River, the largest trout present by far tend to be brown trout with the occasional brown over 10 pounds caught.
The 2011 population estimate is about average for this reach. Being located 42 miles downstream of Gray Reef Dam, this reach can be impacted by high summer temperatures and silt accumulation making it far less productive than sections closer to Gray Reef. It is interesting to note that trout growth in 2010 and 2011 was exceptional with fish at age 1 and 2 being nearly 2 inches longer than is typical for this reach. High water conditions likely served to keep temperatures and turbidity down while increasing invertebrate production and drift.
Big Muddy Access area to Rabbit Hill Access area is the lowest reach that we routinely monitor trout populations on. In October 2011, we estimated 500 trout per mile and 780 pounds of trout per mile which is meeting our population objective for this reach. Over 98% of the fish are rainbow trout with only about 10 browns per mile. Rainbow trout average 15 inches with individuals to 6 pounds captured.
The section from Edness Kimball WilkinsState Park downstream to the Dave Johnston Powerplant is annually stocked with 20,000 fingerling Firehole rainbows. In 2010 we began a study to evaluate the stocking program to see what percentage of the rainbow population are hatchery fish and whether or not continued stocking is justified. While the study will run through at least 2014 to fully evaluate, our results from the first year are interesting. We found that 50% of the 12-16 inch rainbows ( 1 year old fish) in this reach were from the 2010 stocking, and that the stocked fish averaged 2 inches longer than their wild counterparts.
Due to Alcova Reservoir spilling in 2010, 2011 and for a short period in 2012, walleye have made their way into the North Platte. Anglers are reporting catching a few below Gray Reef Dam. There has been some confusion surrounding what to do if you catch a walleye. The restricted creel limits on the river apply only to trout. If you catch a walleye, feel free to keep it (within the walleye limit of course, which is 6 walleye per day or in procession, with no length restrictions).