A stream hike

On October 11, 2014, during a severe drought, I took a hike up into the headwaters of Marshall Run, a North Fork Shenandoah River tributary near Fulks Run, Virginia (see my Profile of a watershed). I wanted to see if any deep pools provided refuge for brook trout. Here are some photos of what I found.

I encountered this old log weir installed by the U.S. Forest Service, presumably to create a deep pool for trout. But the pool was dry--a potential fish killer rather than a refuge. Perhaps a bigger log would have scoured a deeper pool...

Further upstream I encountered the first of 5–6 natural pools. Now this is the real thing...

And sure enough, the trout were still there. Look closely--I see nine.

Here's another pool with trout, but they'll need rain soon!

The largest pool is cut into bedrock. It was waist deep, 30-ft long, and full of trout.

I was happy to see these pools harboring brook trout, even in a severe drought. But the entire population is packed into just 5–6 pools. On another hike 15 years ago I saw a guy walking out with a bread bag full of trout in each hand. One unscrupulous fisherman could easily push this vulnerable population over the edge.

Should this brook trout population become extirpated, due to this impassable culvert downstream (and see my Oral explanation), Marshall Run will not easily be recolonized from other streams in the upper NF Shenandoah River drainage (as would otherwise naturally occur over time).

Thus, although the habitat is relatively intact here in one of Virginia's few remaining 'healthy' brook trout watersheds, this brook trout population is vulnerable. Brook trout are well adapted to thrive in small mountain stream networks subject to frequent natural disturbances (floods, droughts, harsh winters, fires), but local populations isolated from each other by barriers and degraded stream segments may eventually succumb to inbreeding, a severe natural disturbance, or overfishing.