Is that in late fall, winter, or year around regarding finding them over leaf litter. I could understand that perfectly if it is a seasonal habitat shift, which is pretty common among other species. Additionally, if it is a night vs day habitat shift, that’s common too. It could also be both, a seasonal and daily shift. Additionally, leaf litter tends to accumulate most in eddies or slower current. This reduced current is attractive to fish in cold water temps from an energetics standpoint plus the leaf litter there is a provider of macroinvertebrate forage and a hiding place for stream forage fish in winter. Your observation reminds me of finding lake smallmouth over mud bottoms in shallow coves in very early spring or the tail end of official winter. That’s typically that lair of largemouths.
To respond to another comment or two, I found that the streams and rivers of the Susquehanna Basin were the home of generally larger rock bass than those in the Delaware Basin. That observation was not true for all streams and river sections in the Susquehanna Basin, but it was true for all that I ever surveyed in the Delaware basin and I would say that on average it was true for the Susquehanna Basin that rock bass topped out at a larger size. The Susquehanna Basin produces some real whoppers. I’m a little foggy on how large the rock bass tended to be in SW Pa streams and rivers, but they certainly were not any worse than those on avg in the Delaware Basin and I don’t recall remarking or thinking that SW rock bass were particularly small, but I would say Susquehanna Basin RB were exceptionally large at times.
Finally, regarding water temps, I never searched specifically for info on RB temp preferences or requirements in various life stages, although I suspect that I must have seen adult preferences in the past. They just didn’t register in my brain as being unusual for a warmwater species. In the field, however, it was clear that adults had an interesting association with cold or cool water. Regarding the generalized longitudinal shift in stream predators, moving downstream from the headwaters, the shift in predators went from ST to mixed ST/BT, to BT, to mixed BT/RB or mixed BT/Fallfish/and a few SMB. There is and was a definite overlap between BT and fallfish and/or rock bass. The fallfish overlap seemed to gomfor a greater distance than the RB overlap, but I did not see enough of that to make a more definitive statement.
An extreme flip-flop of an RB/BT overlap occurred in the lower portions of the WBr Perkiomen where in the early 1980’s it was a fairly good rock bass stream with no BT found in surveys. By 2007 or thereabouts, the rock bass were nowhere to be found and it was a fledgling wild BT stream. Somewhere in between it must have been a stream with an overlapping BT/RB population.
While I have certainly been an observer of climate change for decades as it has related to my personal experiences with ice glacier recession and my on the scene exposure to rock glacier research/landslide occurrence in Switzerland, I have not been a “sky is falling” proponent when it comes to Pa wild trout populations. Note that I said Pa, not nationwide. Not every region of the US or elevation within the US has the rapid tree and shrub colonization and growth rate that we see in Pa. Within the warmest portion of the state I have seen too many cases of BT population expansion into formerly too warm waters for BT population survival over the course of as little as 8 yrs and as long as decades. While the climate is warming, land use is shifting, riparian vegetation is growing…growing faster and with greater density, and BT are populations are expanding into stream reaches that were previously too warm, and in some cases not only expanding longitudinally but also achieving Class A biomass status. This is the opposite of what I think some would think would be happening. I think this should provide hope, but it should also provide opportunity for intervention in some cases because nature is telling us how to cool or better safeguard some streams.
