I know I went over this in a different thread a while back, but since the topic of mapping and allopatric patches came up again (TU conservation portfolio/brook trout atlas), I thought I'd show some maps that help explain why things appear dire to brook trout
anglers.
Disregarding that we know the allopatric patch assignments are incorrect and that there are patches that aren't represented that should be, here is a map that shows
only allopatric patches from the same dataset that TU used in their conservation portfolio map (brook trout atlas).
That map shows all allopatric patches in Pennsylvania. There are 774 patches listed as allopatric brook trout. Again, we know this isn't accurate, but let's assume that the unrepresented patches cancel out the erroneously labeled patches. For reference, there are roughly 54,000 patches in Pennsylvania. So roughly 1.4% are claimed to be allopatric brook trout.
As anglers, we need patches/streams where we can fish. I used public land and selected all the allopatric populations that are either within or overlap public land. This doesn't account for public easements on private property, but that is likely a very small number of patches overall.
The map above shows patches with some portion of their boundary on public land. The count drops to 571 patches which is roughly 1% of all available patches. It's important to consider that some of the boundary overlaps with public land are very small. Here's an overlay showing public land and allopatric patches to see the overlap. Bright green is outside the public land boundary. The dark burgundy color is our public land areas (SGLs, State forests, State parks, and ANF).
Limiting the allopatric patches to only patches contained entirely within public land, the number drops to 93 patches or roughly .17% of available patches. Here's what that looks like in map form. I'm not going to get into overlap analysis and sorting by percent overlap. I'm just trying to visualize why it seems like we have very little allopatric brook trout water to fish. Again, knowing that the data isn't entirely accurate, it still paints a bleak picture.
It's also worth pointing out that this data was generated in 2006, and from what I can tell by looking at the TU conservation portfolio data, it's identical to 2006 Hudy et al./EBTJV classified catchments dataset. So it's likely that some of these have changed since they were classified in 2006. In other words, we've probably lost populations, gained populations, or lost/gained mixed populations.
The point is, I think there's a sentiment by some that we don't need to be concerned with brook trout because we still have a fair amount of them in the state. The question is/are, how healthy are those populations? Are we gaining allopatric populations or losing them? I know these questions need to be answered across the native range, and I hope we get an update on the 2006 study so we can establish a trendline. I'm concerned about what that will look like, but we need to know.
I know this comes across as alarmism. I'm not suggesting brook trout are imperiled to the level of some cutthroat subspecies in the west, but if we don't start making serious efforts to bolster their populations now, the long-term outlook is going to get very bleak very fast and cause more disruption far into the future when someone has to ultimately deal with it.