BSC Biologist Notes from 2022 Fall Survey

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Thanks for your interest in Blue Springs Creek!  I am the biologist that oversees it and other Meramec basin streams.  We typically survey the wild trout population about every 3 years, and just completed a survey this past fall.  While numbers of fish are lower than we’ve seen during wetter years, there is still a great population of trout in the stream.  I’ve included a graphic showing population estimates over several decades – the population is definitely impacted by the amount of precipitation we get, with wetter years having more fish than drier years.  In addition to total numbers of fish, we look at sizes as well (2^nd graphic) – the management goal for the wild streams are that we have at least 3 year-classes of fish present, so we should see 1 yr old fish in the 4-6 inch range, 2 yr old fish in the 7-9 inch range, and 3 yr old fish at 10+ inches.  I was happy with the sizes we saw this year.   

Regarding the habitat, depth & cover does change over time in Blue Spring Creek – depending on the rainfall event, it can deposit gravel in one flood and scour it away in another flood.  We try to ensure the wooded riparian area next to the stream is in good shape to keep streambanks stable, that trees/rootballs fall in the stream for fish cover at a natural rate, and also provide shade for the stream.  While there are shallow spots with not much fish cover in the area you mentioned, there is enough habitat to hold several year classes of fish through that stretch.  As holes deepen or another tree falls in and creates a scour hole, the fish seem to find those areas relatively quickly. 

is it true you don’t do stream improvements because they wash away all the time?  I would say that’s not 100% correct.  In-stream projects/habitat additions/etc. have been done on several of the trout streams and in the trout parks.  Yes, several (most? I don’t know of a running tally of them kept statewide since many are done locally) of them have become unusable for several reasons: gravel is deposited on top during a flood and buries them, or floods sweep them away or breaks them apart.  One big reason we have not tried any on Blue Springs Creek is the amount of impact the heavy machinery needed to install a structure that can stand up to a flash flood would have on the intact riparian corridor.  There are not many places were we would not have to remove large, mature trees in order to bring the habitat to the stream.  I prefer greatly to let nature take its course and allow the trees to fall in naturally to recreate cover, which happens a lot.  Yes, there are stretches were deeper cover could hold additional trout; however the overall fish population is somewhat stable so I don’t see that instream cover is the limiting factor for them.  Water levels and temperature appear to be way more of influencers than lack of deep holes.  

1. I’m a layman, but I have only seen population estimates in fish per mile.  Is the estimate below from the spring to the river?   I track the population for the whole MDC area (approximately 3 miles).  It does not include what’s above MDC on Camp MiHaska property. 
2. I don’t want to hot hole, but this a debate I hear all the time.  Do you find significant numbers of all class years from the river up to the turn in for the Blue Springs Ranch?  I want to fish it, but people tell me all the time not to waste my time.  Part of the reason I use the area population is that it is significantly different upstream to downstream.  The lower end by Blue Springs Ranch has a less dense (whether you measure it in fish/mi or fish/sampling time effort) – there are all sizes classes present down there, but they are few and far between.  
3. What year do the fish lose par marks?  Usually by year 3 and/or by the time they get to the 8 inch range. I’ve seen some bigger ones with marks, and some 7 inchers without marks. 
4. When they lowered the tunnels below the highway so there was no waterfall anymore… did that do anything to the numbers above and below the highway? That was a natural phenomenon – they have not moved the culverts.  I’ve seen the scour hole fill in one other time when a tree got lodged just right below the concrete apron.  I think it will recreate the scour hole/waterfall again as flash floods come through.  We did not see any overall differences in densities above and below compared to other years, but the scour/waterfall area itself is holding less and smaller fish.  (The ever changing stream bed as evidenced by what can happen with the scour hole during a flood goes back to the top question about why we don’t do more instream habitat work.)

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Thanks for posting this 👍

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What I found interesting the charts is the density of fish in the wetter years... talking 400-500+ fish per mile.  I by no means want to flood anyone out, but come on rain.  I try to never fish the creek in really hot July/Aug weather.  I think I will add a focus to rainfall also.