Population decline?

[wildtrout2]

So, with the super low water levels we experienced this season on MANY Pa wild streams, do you think some will suffer population declines? I can't recall a worse season.

 

[pcray1231]

Some, yes. Others, no. If it stays cold and has enough deep water and/or cover to escape predation, they're fine. But that's not the case with all streams.

It was a drought year but not the worst ever. Just the worst in a while.

 

[Jessed]

I think it depend on the stream. I visited a class a stream today and it was super low but cold and I saw a ton of fish.

 

[Chaz]

Freestone Streams will suffer more than limestone streams. There will be population loss across the board.

 

[troutbert]

Kettle Creek is at 6.8 cfs. The gauge is below the confluence of Cross Fork Creek.

Look at a map of Kettle Creek and tributaries from that point up. Look at all those miles of Kettle itself and all its many tributaries.

Their combined flow is 6.8 cfs. That's a trickle.

Yes, the trout populations will decline from that.

They declined very noticeably after the 1999 drought.

By 2003 they had recovered very well, because of better flows.

The freestoners populations bounce around a lot.

The limestoner populations generally bounce around much less, because they have much better baseflow.

But after the 1999 drought a few of the warmish stretches of limestoners were noticeably down. But also were very good again by 2003.

 

[sarce]

There are probably some small unnamed tributaries that dried up completely. I have heard of trout surviving droughts by burrowing into gravel to get at the groundwater below. It happened when a small Shenandoah National Park stream totally dried up many years ago and when rains returned, the trout repopulated with no stocking assistance (the stream is isolated from other brook trout streams in the park so they definitely repopulated from the burrowers). There are probably a few really small streams that went or are going through something similar right now and could probably use a break from fishing the next year or two. Just my $0.02

 

[724flyfishing]

They'll be down in a lot of places. It will look even worse because the past two years leading up to this mess of a summer were very mild and favorable for trout. Between Mother Nature or the stocking truck, they'll make their way back after a favorable year or two in a row.

 

[k-bob]

I wonder about some streams that are marginal thermally. low water levels (water flows more slowly in unshaded areas) in combination with unusual heat might have increased water temps and lowered oxygen levels?

for example, I have never found choke creek NE of Blakeslee to fish well given its size, but I just tried the newly added stretch in state forest above river road. didn't see a trout. choke has swamp water inputs, low buffering bedrock in headwaters, and slowish flows in limited shade, so not a lot of brookies for its size in my experience. but given the pools I fished, thought I might find a few. i checked dissolved aluminum, which might suggest an acidity effect, but it was low even considering the low flow. (and by the time choke reaches river road, it has run through a longish stretch of catskill bedrock w/ decent buffering)

if it isn't acidity that leads to low brookie numbers, maybe this year choke creek is "too acidic for browns and too warm for brookies?" (choke creek does flow slowly thru a lot of unshaded areas. in previous years, there have been some brookies below the falls on choke but those falls must send the oxygen levels up and maybe there are cooler seeps in that big pool.) however, I also didn't catch any chubs, which may be present in streams w thermal issues for trout. for ex., nearby ash creek has limited shade, brookies and chubs. meadow run w/ a large upstream impoundment has many chubs and just a few brookies. anyone know just how much greater the water temp tolerance of those silver sided chubs/suckers is vs brookies?

oh well cant figure them all out .

 

[pcray1231]

I have heard of trout surviving droughts by burrowing into gravel to get at the groundwater below.

That has always interested me. I have heard of this and it makes sense, as in a lot of cases, a streambed that looks dry really isn't. In normal flows, unless the streambottom is solid bedrock, a portion of that flow is underground through overburden. How much? Well, it varies a lot stream stretch by stream stretch. It goes down to bedrock, which may be the stream bottom or several feet below. Anywhere from 0-100% of flow can be underground. But in MOST summers a lot of the smaller streams appear dry in spots but the holes stay with water and flow. In dry summers there's more of those places, and fewer remaining watered holes.

We have a spring at our cabin. It's naturally a little swampy area on top of a mountain. We dug out a hole and lined it with blocks to create a 2 foot deep spring hole that we use for backup water. This is the extreme headwaters of a brookie stream, but over a mile from the nearest permanent flow. We have found brookies in our spring hole on occasion. Almost white. So they got there underground.

That said, if the stream goes dry in spots but maintains deeper pools, the brookies will be ok. Maybe a slight hurt for those that got caught in shallow water and the coons got after them. If, on the other hand, it has to rely on underground fish to sustain the population for significant portions, well, they won't be extinct and will recover in a few years thanks to "burrowers", but I have to believe the population in such places took a temporary (few years) but severe hurting.

 

[OldLefty]

I believe that a number of freestone streams in NC must have suffered. If I use Young Woman's Creek as an example, for several weeks the water temperature was above 70 to 75 degrees almost every day. Combine this with extremely low flow with the stream gauge recording less than 2 cfs at times which exposes the resident fish to predation far beyond that which may be the norm. These factors can only have a negative impact on a wild trout population.

 

[greenghost]

wildtrout2 wrote:
So, with the super low water levels we experienced this season on MANY Pa wild streams, do you think some will suffer population declines? I can't recall a worse season.

This summer was hot and dry. But the summer of 1988 was worst. Much worst. We were counting days in the 100's (actual temps) not 90's. No rain. Every marginal trout stream was void of fish by August. It was actually a drought that affected the entire country. Thousands of the elderly and homeless died. The worst in my lifetime. So far anyway.

 

[NewSal]

pcray1231 wrote:

I have heard of trout surviving droughts by burrowing into gravel to get at the groundwater below.

We have a spring at our cabin. It's naturally a little swampy area on top of a mountain. We dug out a hole and lined it with blocks to create a 2 foot deep spring hole that we use for backup water. This is the extreme headwaters of a brookie stream, but over a mile from the nearest permanent flow. We have found brookies in our spring hole on occasion. Almost white. So they got there underground.

quote]


Seriously? That's very very interesting!

 

[salmo]

I found this link: http://droughtmonitor.unl.edu/Home/StateDroughtMonitor.aspx?PA

It appears the "drought" is not as severe statewide as it it in the north central part of the state. I don't know how this compares to past droughts in the state. We received about .1 inch in SE Pa yesterday and are expecting a couple of days of rain and cloudy weather in the next couple of days. It will help but not much.
we need a rain maker. See this:
https://www.youtube.com/watch?v=-Zsw04sU6Kc

 

[salmonoid]

I spent a couple days in NC PA on an anniversary outing with my wife. I did take my 8wt rod along for a bit of night fishing but learned from my mistake of four years ago that you can't mix fishing and an anniversary backpacking trip too easily. This is a sizable tributary to Kettle Creek (or was at one point in the year).

The presence of good habitat means that even when the stream bed goes completely underground, there is still some refuge in the pools that remain.

A small tributary that is almost completely underground.

Looking downstream at a dry streambed.

Taken from the end of the log in the photo above.

Taken from the end of the log two photos above, to the left of the pool in the photo above. There is a large pool with excellent habitat sort of visible (leaning tree, root balls, large rocks) and it was stacked with dozens of fish from 3-16". The pool is at least 3-4' deep still and maybe 30' feet long and will be one of the places where the survivors come from.

A tiny bit of stream bed flow.

An almost stagnant pool; surprisingly, when we were hiking up through, at least four fish scattered in this pool, from 3-7" in length. A day later, on the way out, there was not the same amount of activity, but at least one of the fish was still alive. Would love to know what the dissolved oxygen content in that puddle was..

Lots of white bird poop puddles on the rocks of the stream and the only fisherman I saw was a great blue heron that flew over us as we were playing cards streamside Saturday morning. He squawked his disgust at our presence and turned around and flew back downstream.

 

[Mike]

Burrowing into the gravel has been well-documented in at least one or two behavioral studies going well back into the 1960's or early 1970's. ST for sure, RT as I believe I recall as well.

 

[SlingerFlyRods]

Salmonoid, i know that stream well.. ive seen it that low in the drought from the 90s.. took a full year to year and a half for the other well known parts of that stream to rebound as well.

i recognized the hole where it parts between the two rocks into the pool.. fished it this spring before things went south

 

[troutbert]

Salmonid's photos show the importance of pool habitat.

On small freestone streams, during bad droughts, the pools are the places that have water.

The rest of the streambed is dry (or nearly so.)

And trout being AQUATIC creatures...

 

[Chaz]

I've heard a couple of stories when in-stream work was being done a place where the stream bed was dry, when they dug into the SB they hit water and trout.

 

[ryansheehan]

Amazing how nature will find a way. Trout burrowing through the stream bed, wow. Wouldn't the water get warm from the exposed rocks acting as heat conductors? How far down are we talking about when they burrow?

 

[salmonoid]

troutbert wrote:
Salmonid's photos show the importance of pool habitat.

On small freestone streams, during bad droughts, the pools are the places that have water.

The rest of the streambed is dry (or nearly so.)

And trout being AQUATIC creatures...

I'm curious to know what the depth to bedrock is in some of the small freestone valleys. In some places, bedrock is exposed. But in others, there could be several or dozens of feet of small rounded stones that have eroded over many thousands of years. And while the exposed streambed is dry, there's clearly flow occurring at some level. For instance, I have seen fish stack up a few yards downstream of cold tributaries, where there is zero surface flow, but clearly something cool and inviting is moving underground.

The importance of habitat is why I posted the pictures, because they show, on one hand, a stream in rough shape. But on the other hand, they show the places where fish can ride out a year of drought. They aren't exactly thriving, but at least the fish capable of spawning should have a plentiful food supply.