I don’t know if you meant to point that out on purpose or not but your very very right that ground water was not factored into Hudy et Al. 2008 population productive modeling assessment that generated a lot of the stronghold patches. Here is an article pointing mentioning those very concerns you mention.
Climate change is a pervasive threat to coldwater fish populations, and there r...
afs.confex.com
This is why I often say we have mischaracterized what can and can’t be a brook trout stream because these ground water sources, especially on a fine scale, are extremely hard to factor in and can’t currently be put in a GIS layer.
This poor ability to map out springs on fine scale is the reason why I always laugh when some one says “this stream couldn’t support brook trout” or “only browns can live here”. Even if you temp it at on spot at 75 deg F in July, there are pockets, sometimes of very significant size in this state, of ground water upwelling’s. These fish have been using thermal refuge for a long long long time.
A case study I posted recently on the wild trout stamp discussion shows that super coldwater is not a panacea for brook trout when invasive trout species are present. This below study is relevant to this discussion because it shows brown trou actually stop brook trout from using thermal refuge as effectively and points out if removal occurred in many streams occurred brook trout would likely expand their range back downstream and use the better habitat/forage the brown trout took from them.
A new USGS study shows non-native Brown Trout can place a burden on native Brook Trout under the increased water temperatures climate change can cause.
www.usgs.gov
The other thing relevant to your point scarce is that this discussion was actually started to point out that some of our best thermal refuge/spawning groundwater rich habitat in this state has been perverted by hatcheries and can no longer be used in many cases. Think of big spring, Tylersville, Benner, huntsdale, and many many others private and state run.
In summation there are more than a few places we should be fighting hard to conserve native brook trout not on that stronghold map and everyone in the conservation community is generally aware of this limitation for the most part.