AWESOME info! Thanks for reaching out to him!
On Thursday, April 19, 2018 at 8:44:22 AM UTC-4, Tom Moran wrote:
-- On Thursday, April 19, 2018 at 8:44:22 AM UTC-4, Tom Moran wrote:
Folks, I exchanged a few emails with John Odenkirk (VDGIF fisheries biologist) generally on the topic of brook trout in the Difficult Run watershed, and here are his comments in italics below:First, with respect to my misidentification of the creek chub I caught last weekend as a river chub:The fish in the pic is definitely a creek chub (vs. several other sympatric Semotilus species) - you know for sure by the black spot at the base of the dorsal fin on the anterior portion.On when trout were last found in surveys, and if they were believed to be indigenous:I think I shocked the last brook trout in the Diff. Run system - would have been about 1990 or so. It was a large adult. Depending on your definition of "indigenous" - I am not sure they inhabited that system for more than a decade or so based on anecdotal evidence I have heard and the complete lack of any historical sampling data supporting a viable population in eastern counties documenting wild BKT - believe me - many have looked hard for that evidence. We found them (and the Browns we subsequently stocked) in Little Diff. Run and S. Fork Diff. Run - never in the mainstem. We have not been back in decades, but the FX Co. stream team has - they've done a great job sampling and quantifying aquatic resources in the county. They're part of the stormwater group - you should be able to get some reports if you have not already done so. I've got some old field sheets in filing cabinet in the office, and there's probably some data in HQ BOVA (Biota of VA - central database).On stocking vs indigenous:From what I have heard they were stocked in the 1970s by a person(s)/club but was unauthorized. Apparently, there was some natural reproduction, but build-out of the Government Center (ironic, yes?) and associated commercial area off I-66 around Fair Oaks sealed the fate (e.g., habitat crushed by warmer water and sediment). We tried browns for three years following BKT extirpation in mid 90s, but even they could not hang. Each year class sequentially disappeared the following year in almost the exact same declining linear trend based on quarterly sampling.As to if there were ever indigenous trout in Difficult Run, I located a couple of papers that refer to an 1899 study that found them, and another 1915 one. His comments below:ASPECTS OF THE ECOLOGY OF AN ISOLATED POPULATION OF BROOK TROUT (Salvelinus fontinalis) IN FAIRFAX COUNTY, VIRGINIA
JEFFREY E. LOVICHJournal of the Pennsylvania Academy of ScienceVol. 65, No. 3 (March, 1992), pp. 107-111I have seen that 1915 reference before, but I think it's a bit sketchy. I have seen Lovich pub, but it's been a while. My guess is that if the report of their existence around the turn of the century was correct (and, it probably was), they didn't last long and were extirpated once only to be restocked later (and extirpated again, or maybe for the third (or fourth) time. Probably each incident resulted in limited (short-term) natural reproduction. Just a guess...On Wed, Apr 18, 2018 at 11:57 PM, Andrew Sarcinello <andy...@gmail.com> wrote:John, that is so cool that you actually have a picture of one of those brookies! Thanks for sharing! I can imagine it was at one time a pretty productive stream. All those tributaries would have made for a healthier population. But a highway interchange built right on the headwaters is about the worst thing imaginable for a brook trout stream.
As for the fish in the pond, the description sure sounds like a brook trout, and they have been known to survive in very low densities for long after the majority of the population is depleted. Many Gunpowder tributaries are a good example of this. There is a stream near my parent's house in PA where every few years I will randomly see a lone brook trout even though it is a very good brown trout stream and electrofishing surveys have never turned up a brook trout. They are quite good at finding a way to barely hang on, and I actually don't think road crossing themselves are a death sentence to these fish because the deep culvert pools can provide refuge when stormwater impacts have wrecked literally every other potential hiding spot on the stream.
Interestingly, the USGS gage on lower difficult run has a water temp reading. Last year it peaked around 80. While that is harmful to brook trout reproductive health it is not definitively lethal, though it's close for sure. Imagine that the headwaters and tribs are a couple degrees cooler and now you're talking about something they can certainly survive, though with a lot of stress. Now, whether there is suitable spawning substrate and in stream cover for them to sustain a population... doubtful.
I wouldn't say it's totally impossible for there to still be a few brook trout hidden in there somewhere, but I do think it's extremely unlikely. If the fish seen in the pond was indeed a brook trout, there's always the possibility it was brought in by bucket from some mountain stream. And, of course, maybe it wasn't a brook trout at all.
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