FFIM

I was having an interesting conversation with a work buddy of mine today who grew up on a river in Wyoming well below what's considered trout water -- more about carp, tending to be more muddy, lower gradient, warmer, etc. He showed me some pics of some nice rainbows recently caught on the old homestead and commented that he'd caught a small brown there last weekend and it was only the second one they'd ever seen caught up there, while they always do pretty well with rainbows in the fall. I think his family's place is in high desert, ~80 miles below a tailwater.

I have also noted on another freestone river section in the same general area that there seem to be more rainbows lower down where the water is warmer/muddier, while I see more browns further up in the colder tributaries of the same drainage.

What gives?

I'd always put trout in order of habitat preference for cold water going basically cutts, brookies, rainbows, browns. Why would rainbows do better than browns in these mainstem warm river sections? Better spawning success than browns for some reason? Better at migrating longer distances from spawning to eating to winter refuge to summer refuge?

Not knowing specifics, I’ll just say the rainbow trout tend to like slower moving water more than brown trout. That’s not yo say they don’t like moving water- they like that a lot, too- and at places like the Madison near $3 Bridge- the browns live in the slower edges while the bows live in the faster current. But the easy living of slow moving, flat gradient sections is, in my experience, good water from growing fat rainbows. Your friend may also be seeing migrating cold water fish on large feeding forays during the cooler weather months.

Unless there is a local trib with suitable spawning and rearing habitat, or escapees happening from someone’s private pond, I’m guessing those are drop down fish. 80 miles isn’t that far for a fish to swim.

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"You never miss the water until the well runs dry" - traditional blues

What Dave said. Also--which species is stocked upstream in the reservoir or the tailwater?

Contrary to popular belief, Wyoming stocks a lot of trout--mostly rainbows. https://wgfd.wyo.gov/WGFD/media/content/PDF/Fishing/Stocking%20Reports/WGFD_FishStocking_Report_2018.pdf

That's a good point Jeff. They may be stocked trout put out by Wyoming as part of a put and take program as well. It's not like we don't stock a LOT of trout into non-trout habitat here for that very reason...

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"You never miss the water until the well runs dry" - traditional blues

Thanks, y'all. We're talking about the North Platte here, near Casper and then again higher up above the reservoirs and tailwaters. They do stock the tailwater with rainbows, with wild browns. The actual river miles from the tailwater down to home might be more like 100-150. They do also get wild spawned rainbows in that stretch -- they protect a section for spawners and they have the spawning terrain.

There are spring-fed tribs all over the place up there for fish to use as refuge. Same guy was telling me about fishing this limestone creek 18 inches wide and neck deep with 20 inch trout nailing your fly if you can just get it in the water without spooking them.

So what's the deal here? The rainbows just move around a lot more and prefer the slow water whenever it's not too warm?

Up higher, above the reservoirs (we're talking maybe 300 miles upstream), I think pretty much all of the fish are wild -- you see a lot of short fat rainbows (8 or 9 inch footballs). And I just see more rainbows the further down you get.

It's fun to ponder these kind of puzzles -- the where the hell did these fish come from puzzles. I guess they swam. And swimming downstream is easier than upstream!

I think Jeff and I are going to need a site visit prior to further comment.

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"You never miss the water until the well runs dry" - traditional blues

It's taken radiotelemetry studies to figure out even the relatively short (10-20 mile) migrations of brook trout in the Rapid, Magalloway, Diamond, and Roach rivers. Just get the entire Platte wired up with receivers, then mark fish in all the stocked and wild populations, and hire a team of graduate students to crunch all the data . . . . .