High Water > Trout Spawn

[afishinado]

The high water levels this summer through the fall have benefited wild for the most part, keeping temps down and making fish less susceptible to predators. The is especially true for the smaller streams that often dry up and warm up in the summer.

Now that the fall spawn is here, how does the higher flows in the bigger streams effect the spawn, if at all? Just as an example, this weekend Penns and the Little J were flowing 10x their normal flow at near 2,000 cfs vs a flow this time of year normally close to 200 cfs.

Is this rain too much of a good thing for too long a period for wild trout?

(Let's not even talk about the washout of smallie fishing this season in PA rivers and larger streams.)

 

[PennKev]

I think that the all the high water could result in bigger, healthier trout in those streams going into next year. If the trade off is a poor spswn, it could be an acceptable trade on watersthat have strong trout populations.

That's making a lot if assumptions and guesses though. The truth is I have no clue how this year's rain will affect those streams. All I know is that our wild trout will be fine in the long run and next year we are just as likely to be fretting about a hot dry summer so I'm not going to worry about this year's conditions too much.

 

[edhank]

Would this higher water cause trout to build their redds in places that would normally be out of the water? If water levels drop, would the alevins die?

 

[sarce]

I'm hoping that all the rain has flushed out a lot of silt from the spawning areas. I'm also hopeful that higher flows will make it harder for anchor ice to form this winter. Past two winters with low flows and brutal cold snaps were very rough on the marginal streams and those streams NEED these conditions to recover IMO.

 

[Vaughn]

I was wondering about this too. Specifically the affect of a scouring flood event on redds once the spawn has started.

 

[JackM]

The strong will survive!

 

[bigjohn58]

edhank wrote:
Would this higher water cause trout to build their redds in places that would normally be out of the water? If water levels drop, would the alevins die?

This would be my guess. As long as water is high when they spawn they are going to be picking out different spots from normal years. If thats the case then hopefully the water stays on the high side then the spawn should be just fine. If we go in a dry spell and the water drops a ton the eggs won't be in good locations causing a poor spawn.

 

[JasonC]

I wouldn’t know how to predict what would happen but I’m sure the streams have experienced high waters during spawning season in their histories and the trout are still there after thousands of years for us to appreciate the little gems. They’ll survive just fine!

 

[Tigereye]

From the link: Effects of extreme floods on trout populations and fish communities in a Catskill Mountain river


"Unlike brown trout that exhibited a marked increase in YOY following the flood, the density of YOY rainbow trout was essentially unchanged between 2011 and 2012 (Table 2). The divergent responses of brown trout and rainbow trout populations to the summer flood could be explained by competitive interactions. Brown trout are autumn spawners, whereas rainbow trout are spring spawners, and thus, YOY brown trout emerge earlier, are larger and may outcompete YOY rainbow trout (Gatz, Sale & Loar, 1987; Strange et al., 1992). Conversely, the autumn spawning of brown trout increases the risk of egg loss if autumn or winter floods occur. Several investigations showed that YOY brown trout or brook trout were generally more numerous than YOY rainbow trout except during years when floods scoured the eggs of the autumn spawners (Seegrist & Gard, 1972; Strange et al., 1992; Warren et al., 2009)."



https://onlinelibrary.wiley.com/doi/full/10.1111/fwb.12577

 

[ryansheehan]

This is slightly anecdotal but the last time the Savage river had similar flows it was the best yoy I can remember. There were probably many factors beyond just flows that led to such a good year. I'm sure some river systems will benefit while others may struggle. My biggest concern is a dramatic drop in flow but that doesnt seem to be in the cards.

 

[troutbert]

Penns Creek is at a high level for fishing, but it's not near flood stage.

According to the USGS, it's current flow level is at 4 feet and flood stage is at 8 feet.

I don't think the current flow levels are high enough to create a lot of scour.

 

[Mike]

In Pa, higher Autumn flows favor BT year class strength; low flows favor ST year class strength.

 

[troutbert]

Mike wrote:
In Pa, higher Autumn flows favor BT year class strength; low flows favor ST year class strength.

What are the causes of that?

 

[afishinado]

Mike wrote:
In Pa, higher Autumn flows favor BT year class strength; low flows favor ST year class strength.

^ That's interesting. Any explanation or theory as to why that would be?

 

[Nymph-wristed]

I have seen redds this season closer to the banks + hidden under overhead cover. If they go shallower perhaps they also go more hidden, just like they do as adults. How many big pigs have you kicked out of logs or undercuts in less than a foot of water? Me? Plenty. I think they have this survival thing down pat by now.

I also like the idea that fewer YOY means a couple years of bigger fish before it swings back.

 

[Dave_W]

My guess would be that this year's conditions will not impact trout spawning and YOY numbers next year. To the contrary, I would expect good trout fishing across PA next year. And not just in small freestoners and marginal valley run-off streams - the CV limestoners have more water in them than I've ever seen for this time of year and I think this a plus.

More to the point on wild ST and BT survival: the water levels we have seen this year have been consistently high for long periods and this has introduced a degree of stability that would favor spawning and survival success (I think). In addition, it has been my observation that the high levels this year have definitely cleared sediment and leafy debris. I cannot recall ever seeing so much polished gravel as this year.

With respect to Mike's observation that ST suvival is poor and BT high in years like this. . . .
Might I speculate that this may have something to do with waterway size(?). Since ST tend to occupy smaller, higher gradient headwater areas, they are in a habitat that rises and drops more rapidly than downstream areas were BT dominate. Also, perhaps, the native PA ST's genetic make-up is evolved to thrive in environments with more stable, primeval forest habitat and the recent removal of this (barely more than a century) has created watersheds that rise and fall faster than our ST's are evolved to adapt to(?). If this theory holds water (pun intended) then our state's maturing forests may be a good harbinger for future ST survival.

(Again, just speculating here)

 

[afishinado]

Found this study on flow relating to waters in our area >https://www.state.nj.us/drbc/library/documents/TNC_DRBFlowRpt_dec2013.pdf

Long read but some interesting stuff.

 

[salmonoid]

From the above linked publication:

Fall marks the beginning of the spawning period for brook and brown trout and several studies describe the
interrelationship of low and seasonal flows to spawning success and egg and larval development. A decrease in
groundwater or surface flows may reduce access to and quality of redds during salmonid spawning, and several
studies have found that localized groundwater contributions attract salmonids to habitats capable of supporting
egg and larval development over winter and through the spring (Hazzard 1932, Raleigh 1982, Curry and Noakes
1995, Curry et al. 1994). Similarly, over a three year study on small streams in New York, all observed brook
trout redds were constructed either immediately below springs or in places where seepage entered the redd
through gravel (Hazzard 1932). In addition to groundwater contribution, depth and velocity are also critical to
suitable spawning areas. A regional IFIM study predicted a loss of 10% of habitat loss for withdrawals of 11 to
14% of the November median (Denslinger et al. 1998). While extreme low flow conditions may reduce extent of
spawning habitat in some systems, an analysis of brook and brown trout biomass before and after the 1991
drought showed that low flows during fall could actually increase brook trout spawning success and these
periodic fall drought conditions may give brook trout a competitive advantage over brown trout where the two
species coexist (Greene and Weber 1993).

The Greene and Weber citation is for:

Greene R. and R. Weber. 1993. Statewide 1991 drought study analysis: Pennsylvania Fish and Boat
Commission. Harrisburg PA. 12 pp

Perhaps that is what Mike is referencing, but it's one study, and doesn't mean the converse is true (i.e. if low flows favor brookies that high flows favor browns).

 

[Mike]

Yes, the study was at least half of what I was referencing. A keen observer would see the rest with enough wild trout stream surveys under his or her belt and a nice size staff of numerous crews with which to discuss annual field season observations.

 

[troutbert]

salmonoid wrote:

While extreme low flow conditions may reduce extent of
spawning habitat in some systems, an analysis of brook and brown trout biomass before and after the 1991
drought showed that low flows during fall could actually increase brook trout spawning success and these
periodic fall drought conditions may give brook trout a competitive advantage over brown trout where the two
species coexist (Greene and Weber 1993).

The Greene and Weber citation is for:

Greene R. and R. Weber. 1993. Statewide 1991 drought study analysis: Pennsylvania Fish and Boat
Commission. Harrisburg PA. 12 pp

Why are they assuming this is related to spawning conditions?

It could have been related to survival differences during the worst part of the drought, i.e. when the water was at its lowest levels, which typically happens in the summer, well before spawning time.

A higher percentage of brook trout, and especially a higher percentage of mature fish capable of spawning, might survive extreme low flows than is the case with brown trout.

Simply because brook trout mature at a smaller size than brown trout. And small trout survive better when the water is very low than large trout.