When is warm too warm [Archive] - Fly Fishing Forum

: When is warm too warm

07-31-2003, 11:31 AM
So last night I went up to the river and did a couple of hours of fishing. Wading wet I the water felt warm so I took the temp and I got 68. I did fish for the next two hours but didn't touch anything but I felt guilty the whole time because of the temp and if a miracle happened and I hooked a fish what stress would I be putting on the fish. I went back and forth and I hope if I would have hooked a fish I could have followed through on what I set for myself in that I would have broke it off after a very short time.

I don't think I will be up on the river until the nights cool down more then they have been and no more evening fishing. So it looks like it won't be until next week.

So do you think that we should close rivers down at some point if water temps get to high. I hate feeling guilty when I am fishing and felt like a two face jerk by fishing for a a fish I say to love and want to perserve in those water temps.


07-31-2003, 12:33 PM
Howdy Jeff, I don't know the rules and species for the river mentioned in your post but unless it is strictly a catch and release river for all species during the hot weather I would not be for letting some part of a govermental agency decide this for everyone. In my opinion there is a great trend in this counrty for letting the goverment take the place of personal responsibility. The more this is done the more freedoms we will lose. I am not judging you as a person because you went fishing, I'm just saying that if YOU thought the river was to hot for fishing then YOU should of not of fished. The next guy may not have the same feelings or opinions as you do. Take care, MJC

07-31-2003, 12:56 PM

I totally agree. I am not for more government regulations. This was a we as fly fishers might want to think about regulating ourselves but if we can't there might need to be a stronger rule to protect fish. Also I fish for Steelhead 95% of the time if not more and where it is C and R on wild fish.


07-31-2003, 05:19 PM
If the water temp really was 68 degrees, I'd be suprised. I know of others that have registered temps of 55 to 58 degrees depending on the time of day on our W Washington rivers, but no others in the 60s.

Is it possible you tested in shallow water, or in the sun??

Either way, if I felt it was too hot for the fish to handle the fight but I just had to keep fishing I'd put on one of my ultra-lightwire barbless scud hooks (one of the advantages of tube flies). A bit of pressure, the hook straightens and Mr or Mrs Steelie is on their merry way.


07-31-2003, 05:39 PM
Yes I really did get a 68 in swifter water and I took it twice because I didn't believe it. I was shocked to. I went to lighter tippet and new I could break it off.


07-31-2003, 06:52 PM
I have been fishing without a thermometer for far too long. That in spite of a good friend giving me a gift certificate to go buy one.

I do know though that the water temps on the river Jeff was fishing are in the 60s. I fished it yesterday morning with just shorts under my Pategonias and the water was quite warm. I heard on Sunday a reading of 64 so I think 68 very likely.

I like Doublespey's idea of the light wire hook. I have been going with heavy tippet (13#) so that I could horse the fish in. Of course that presupposes being able to entice a fish to take and we all know that is impossible.

07-31-2003, 07:00 PM
These temperature readings are not surprising me at all. I took a reading over a week ago and the thermometer read 62 after the sun had left the water.

The forecast is calling for cooler temperatures but alas, no rain! :(

07-31-2003, 08:21 PM

The temp of 82 today here in Mount Vernon was a very welcome relief from the 90+ we have had the past 4 days. On a another note, only George and I shared the Flats Saturday eveining, and neither of us took a fish. In fact, George has not gotten any so far this summer. It sure is a strange year.

08-01-2003, 09:15 AM
Not surprised at the temperatures being reported, at least here in Western Washington.

Two of the USGS gauges have thermographes that recorded daily high temperatures above 70 degrees this week - South Fork Nooksack above Skookum Creek at nearly 75 degrees and the Cedar at Renton at 70. On Monday evening (7/28) I took a hand held temperature on the North Fork Stilaguamish at Arlington that was 78 degrees. In past years under similar conditions I have seen temperatures on lower Deer Creek (NF Stilli) exceed 80 degrees!!

Obviously under such conditions the fish are very stressed. They only survive by finding cooler waters. This generally is located in deeper pools that have ground water inputs through the pool bottom. Such spots may 10 or more degrees cooler. Such fish are difficult to take with swung flies as the fish would have to venture into the warm water however they are can be taken when forced feed "jig flies".

Something to think about - Our summer steelhead as they enter the rivers are bring with them all the fat reserves that they have to maintain themselves until spawning. If the fish exhaust this reserve they will not survive to spawn. It is not uncommon to see some females run out of fat reserves and begin to re-adsorb their own eggs to stay alive - needless to say they don't spawn successfully. Following summers such as this becomes much more common. It just takes more energy for the fish to stay alive when they are stress in such conditions. Unlike trout that can replenish their reserves when conditions return to more favorable temperatures the steelhead can not. Certainly current conditions are pushing the fish nearer the metabolic edge of survival. Any additional stress under these conditions is not benefical to the fish. I'm not sure that the fish can afford any additional stress - and I mean any - that includes even the metaboloc cost of being caught and released once the water cools. How do we know how empty their tank is? And whether they have enough to last to next spring?

A question for those that prefer no government restrictions - Can I asssume that you also dislike fly only restrictions, or no bait allowed (selective gear), or bag limits, or wild steelhead release regulations? - all State imposed restrictions. Or is it that you object to such interfenence only when your own fishery is being threatened?

Whether we fish, or when we fish again, or how we fish of course depends on each of our own ethic.

Tight lines

Rick J
08-01-2003, 09:28 AM
The Klamath in N California often runs in the 70+ range in the fall. I think the fish must be better adapted to these high temps. though you do need to spend some time reviving some of the hotter fish that takea bit of time to bring in. I also like the idea of the small light hook. I apply a great deal of pressure to get the fish in quickly and do not much care if it pulls loose. Once he has been on for awhile I will take more care as a fish that pulls loose after he has fought hard will have less chance of survival than if brought to hand and revived.

Regarding the closing of rivers I'm not sure I totally agree with MJC. I know that my favorite trout stream, Silver Creek, seems to have been hit hard by some calamity over the last couple of years that is likely related to some extent to warm, low oxygenated water. The Conservancy was asking that folks limit fishing to certain hours. If a watershed is threatened due to adverse conditions and can be monitored by fisheries biolologists - these guys have the most information available to make an educated evaluation on when it might make sense to shut things down.

There is a run on the Klamath called Blue Creek where cooler water from a tributary enters - there can be literally hundreds of steelhead and silvers that hold up in this run and just get hammered. I have been in favor of DFG closing this reach of river during certain times when river flows are low and hot and the fish are not spreading out through the system.

08-01-2003, 09:39 AM

I have voluntarily stopped fishing the NF Stilly for the reasons mentioned in this thread.

It appears to me that Deer Creek does not have enough water for fish to migrate up the stream. I would assume that these fish would start to stack up in those sections directly below the mouth of Deer Creek perhaps making them far easier to hook and possibly allowing the fish to be hooked multiple times. In this time of low water and high temperatures this could be a death sentence to those fish staging to go up Deer Creek. Given the high temperatures and the low water conditions does WDFW, at some point, consider closing certain areas to fishing?



08-01-2003, 11:22 AM
While I am always against more government intrusion into our daily lives, I'm not against all government imposed restrictions. On rivers with a varied fishery I would be opposed to closing the whole river to benefit one species, or segment of the fishing population. In my opinion this just causes alienation between fisherpersons of different persuasions which is already a very large problem to the determent of all fishing resources.
Rick, I would not necessarily be opposed to closing your favorite trout stream to benefit the fishery during warm water, and I'm not opposed to closing certain reaches of a river, however should your favorite stream have a warm water fishery in it's lower reaches than I would be opposed to closing the whole stream.

08-01-2003, 11:51 AM
I guess I'm just suprised at how warm our Western Washington rivers (or more accurately creeks) can get. I used to take temps regularly during summer steelheading outings and only remember an occasional reading approaching 60 degrees.

Do others remember our local rivers regularly getting into the mid/upper 60s? Is this another aspect of global warming? :eyecrazy:

Next time I go to the river, instead of fishing I think i'll just throw in a few handfuls of icecubes!

wet fly
08-01-2003, 06:13 PM
I will list some of the warmest temps in the past hot spell. NF 8-29 at daylight. 64 F. 8-29 lower river at 3 pm 73 F. 8-30 lower river at 3pm 74 F. This morning at 8am below Arlington 65 F. My thermometer is calibrated and these reading were taken in the faster deeper water. Over the past 20 years or so it is not unusual to have over 70 F on the warmest days. The 74 F. is the highest temp reading I have ever taken in the lower Stilly. It is very important to have as many shade trees as possible along the river. Jerry

08-01-2003, 08:42 PM
Kerry -
I have been concern about whether the fish can get up Deer Creek since early June. Just not very much water. In the past WDFW has closed the North Fork at the mouth of Deer Creek several times. See -

Rick -
If your fish are need of being revived then they are pretty stressed. This would be doublely so if you had played them hard (quickly) and they still need reiving.

Doublespey -
I have also noted that the stream temperatures are higher than 20 years ago. The water below Oso would rarely get about the mid sixties and today it maybe 10 degrees warmer. Believe this is due to a combination of factors:
1) Weather pattern changes have resulted in lower snow packs, and shrinking snow fields and glaciers.

2) Increased bed load inputs have resulted in wider stream channels and shallower pools.

3) Less shading from ripparian zones - due in part to the wider river beds.

4) Lower ground water inputs (springs) due in part to increase use of ground water for domestic uses.

Tight lines

08-01-2003, 08:59 PM

Although the Oso area is one of my favorite places to fish, I think it might be time to close the Stilly from the bridge at Oso to the Hell Hole. This would provide the fish some sanctuary (event hough I am aware that it will cause some to get angry about the closure) that I think they need this year because of the higher river temps and resulting using of energy reserves more quicklyt than normal.

I am worried about any Deer Creek fish that make it up to Oso being hounded and stressed because it is obvious they are not going to make it up Deer Creek until we get some good rain. And that is probably not going to happen until sometime in September.

08-01-2003, 09:39 PM
Flytyer -
I don't disagree however I would expect that the emergency regulation (address posted in my previous posting) should buy them and the other salmonids in the North Fork some relief.

Let's all hope that the ninety degree days are behind us!

Tight lines

08-01-2003, 10:22 PM
It is times like these that I do a little exploring and am open to the idea that there are fish out there worth catching besides steelhead. :hehe:

Mountain Stream Trout
Bull Trout Where They Are Open
Saltwater Salmon
Etc. Etc.

Rick J
08-01-2003, 10:37 PM
Some steelhead and trout just sorta roll over and just come in but a screamer that takes off is going to get stressed to some degree and water temp certainly makes it worse. I have made it a habit to spend a bit of time with most fish I hook - be it a steelhead or a trout to make absolutely sure it is in good shape when is swims off. I often wonder when folks brag about never touching fish and using quick hook releases. A large fish generally should be revived prior to release and that requires you carfully handle the fish

08-01-2003, 11:27 PM
Rick -
For the various salmonids the popular fly fishing literature and fishing shows generally agree with your position. So much so that it has become the conventional wisdom of the angling world. However my experience and observations would indicate otherwise. The handling of the fish that is need to revive the fish needless prolongs the time it is confined (controlled) by the angler thus the period of stress.

Let's take the most extreme case - a bleeding fish. I commonly see folks craddling the fish and attempting to revive it. It is my position that fish's blood if given a chance will clot quickly - if that wasn't the case they would quickly bleed out from any injury. In the process of trying to revive the fish we continue to place the fish under some stress and likely its heart rate remains high - thus preventing the clotting of the blood quickly - extending the period of bleeding thus the likelyhookd of death. It is much better to quickly release the fish in a quiet location with little current flow (an eddy, under a log etc) thus allowing its heart rate to slow and give the fish a chance to revcover.

It is my firm belief that if the angler attempts to land a fish by breaking its will to resist rather than fighting it to exhaustion reviving it is not necessary. By breaking its will to resist fish can be controlled and land long before the tradition landing point of it rolling on to its side. This is even the case of some large fish on relatively light tackle.

It has become my position that if an angler finds the need to revive more than the very rare fish that he/she is not "fighting" the fish aggressively enough.

In additon to trying to break a fish's will to resist I often will give the fish slack line prior to the final stage of the battle and hope that it shakes the barbless hook on its own. If I run in to the ocassional very stubborn fish (typically a large narly steelhead male) that I can not goad into playing my game I just point the rod at him a break the leader. To me the lost fly is a small price to pay to avoid placing undue stress on the fish.

I freely admit that my position is unorthodox and flies in the face of the conventional wisdom. However I have given the handling of fish a lot of thought and carefully observed the responses of a fair number of large fish landed by myself and fishing partners and believe this approach is the best for most released fish. I encourage you and others to give it some consideration.

Tight lines

08-02-2003, 12:42 AM
I agree with smalma. On the exceedingly rare occasions that a fish does go belly up (usually warm water), then I prefer to hold the fish facing upcurrent in soft water until it regains strength to stay upright. Personally, I never understood the notion of forcing the "back and forth" motion to get water in a fish's gills. Fish don't often swim backwards, but they'll fin in the current and let water pass over and through their gills when tired.

wet fly
08-02-2003, 12:45 PM
I think it is best to get the fish back into the current as quickly as possible. Each fish can present a challange depending on the water speed, depth, type of bottem and the size and will of the fish. My first choice is to wade out to thigh deep water and grab the fly with a pliers. I have on occasion reeled all the leader and fly to the tip top and dislodged the fly as one would do with a snag that is out of reach. At times this can result in a quick release. I have seen some pretty clumsy releases over the years to the detriment of the fish. If I had a video camera of some they would have made the comedy show. If done right one can be satisfied that the fish will make it. Jerry

Rick J
08-02-2003, 01:20 PM
I agree with loco_alto regarding moving a fish back and forth to some extent. I am a part time guide and have had to deal with a number of stressed fish that clients have not landed quickly - both trout and steelhead. If the fish is highly stressed you will sometimes note that the gills are not moving. If you are holding it by the tail with a hand cradeling it just behind the gills and you give it a tug backwards, this will flair the gills open and often this will start the gills working on their own. At this point, there is no need to move it back and forth but you still need to hold it upright in light to moderate current until it gains strength and can swim away on its own accord.

Smalma - I think you are right when you indicate if you fight a fish with athority it will often need little or no reviving. And you are right about a bleeding fish. There is a belief out there that a bleeding fish will die but this is not so. At hatcheries, biologists will sometimes take gill samples causing the fish to bleed but the fish survives.

I still feel comfortable holding the fish by the tail - often the easiest way to get a hook loose and just get an understanding of how strong it is- if it tugs to get loose, I let it go - if it, for some reason, appears sluggish, I will hold onto it until such time that it appears ready. If a fish is obviously not stressed, I will just unhook the barbless fly - usually the case with half-pounders.

08-06-2003, 02:43 AM
Sparkey, the pisspoor steelheading has caused me to try backup plans also. I fished a local beach for pinks Saturday evening and floated the Skagit for dollies Sunday. I hooked nothing Saturday when humpy fishing and what did I catch near Marblemount Sunday while fishing for dollies? An F'ing humpy.

08-06-2003, 05:31 AM
My opinions on warm weather fishing are not scientific but based on observation which I have a pretty good amount of. I've seen belly up fish and I've had vibrant releases and here are factors to consider in attaining the latter:

The biggest problem I observe is the use of inadequate weight gear for full-sized steelhead. It's pleasant to use light gear in summer but some gear is just plain too light for the good of the fish. For spey rods I won't use anything less than a solid 7wt, and for single handed rods nothing short of a solid 8wt in warm weather. The lighter rods are good for trout and half-pounders, but not steelhead and atlantic salmon.

Get the fish in as fast as possible and let them get back into their lie. Even if a longer rod requires more leverage from the angler, the spey provides much more force and more powerful butt. He might work harder but the fish is moved much more per pump.

100% Barbless hooks. The faster and easier the fly is removed the better. Who cares if you drop one while photographing it once or twice, it's better than struggling to get the hook out or having to use pliers. Carry something to remove the hook quickly without handling the fish. Glenn LeGrand at Camp Bonaventure gives his guests a hookout tool for the vest, very nice touch.

Land and keep the fish in oxygenated water. As the fight wanes, I am always looking for the right spot to land the fish. Although the frog water might be best for me, I opt to bring the fish close to the chute or riffle for a fast recovery when water temps are high. Try it, it really works.

Well it sounds like the hot spell has snapped in the PNW. Cooler nights and freshets are right around the corner and I hope to be practicing release methods very soon! :smokin:

08-07-2003, 09:59 AM
Juro -
I have to disagree with some of your opinions.

By far the largest problem I see with anglers fishing in warm water conditions is the fact that they are fishing. I would not expect better from newbies but would hope that those esperience anglers with a true passion for the fish would be able to put aside their need to fish for the need of the fish.

Rods are just tools for the fisherman and it is the angler using those tools that mis-play the fish not the rods. With today's modern materials one is much more able to take the fight to the fish with some amazing little weight rods without unduly stressing the under most conditions. I do agree that in-experiene anglers or those having trouble landing fish without beating them to exhaustion should probaably stick with the large sticks. My measure of whether the tackle is too light for a given angler is whether the fish being landed needs to be revive or not. I would be more inclined to "tip" my hat to angler using a 5 weight that doesn't need to revive his released fish than one using an 8 weight that has the need to revive most fish.

As a practical matter rather than rod size it is often the leader strength that determines how aggressively one can take the fight to a fish. The rod's action and hook size can also paly a role.

You mentioned photography - why would anyone want to take a picture under these stressful conditions?

Could not agree more on the use of barbless hooks whether required or not.

Where possible it is good to release the fish in areas near cover so that they can calm down (get that heart rate down) as quickly as possible. Cover can be water depth, chop, shade, logs or other cover. I prefer not to release my fish in riffle water if at all possible. While there are often are good cover in such water it may take some time for the fish to find those soft spots out of the current - prefer to release them near other more obvious cover. It is a fallacy that the riffles may provide the most oxygentated waters - The surface dissolved oxygen levels in the riffle and the pool typically are nearly the same. Often (especially if it has held a fish) the deep water of a pool (the bottom layer) will have as much or more oxygen as the riffle. The amount of oxygen water can hold is dependent on its temeprature - the lower the temeprature the more oxygen (parts/million) it can hold. Thus those deep areas feed with cool ground water may actually be more oxygentated.

Some of my thoughts

Tight lines

08-07-2003, 11:04 AM
Enlightening comments, Smalma.

I think you hit it on the head, it's what the angler does that matters. I am no icthyologist but I interact with a lot of fish. Truth be known my comments were targeted toward an increasing number of anglers who use ultralight gear in summer when conditions are not ideal for the fish. None of my comments were meant to help anglers rationalize fishing under stressfull conditions.

However I feel compelled to clarify that abstaining from fishing is one of my opinions under stressful conditions and one that I practiced frequently. Perhaps we need to close waters based on conditions as a general rule, I'd be all for that. But I am assuming there is such thing as water conditions where it's acceptable to fish, yet what the angler does controls the welfare of the released fish. In other words, conditions under which bad anglers will harm fish but good anglers would not. These are the conditions I am speaking of.

I also maintain that using the same angler as a control, he/she can bring a fish to hand much more quickly with an 9wt rod than a 6wt rod regardless of tippet, which pops if too light shortening the fight to the fish's benefit. One could profess that the ideal tippet would be so light the fish always pops it after the grab, low impact, fishing for the take. So it's possible to argue that light tippet is good for fish. But I won't go there.

My experiences in releasing fish have been that they do better where more water passes through their gills even if the relative saturation is not at it's peak. As an angler and without suitable monitoring devices there is no way I can determine O2 levels in a manner suitable for fish revival so I take the fastest action possible to land the fish where more water passes thru the fish's gill without any action on the fish's part. If I land the fish in a stagnant cove convenient for me, I can not determine whether the O2 level is superior or not. But I do know that for every 10 seconds I am holding that fish, he is not acting as well off as the one I released in a moderate flow.

Purely anecdotal, but until I can somehow determine where the oxygen is in my landing zone, I will have to act based on the feedback the fish has given me. They do act more frisky when I release them in current.

Also, the vast majority of summer run steelhead pictures of fish I've caught are still in the water and stay in the water. You may see some hold-up and grin shots of winter fish from me, but they are a small minority percentage.

But you raise a very good point - stressful water should not be fished in the first place. Unless we get some rain, I will limit my fishing on the upcoming visit to those waters where temperature and oxygen are adequate for fighting fish.

I hope enforcement and regulations move toward condition-based closures in the future as well.

BTW - thanks for the tip on "cover".

08-07-2003, 01:20 PM
Juro -
Speaking of cover -

Many anglers continue to believe that fish are in the riffles during low flows becaused higher oxygen levels. I argue that they are there because of the cover the choppy/whitewater provides. I have had a number of opportunities to fish wild winter steelhead in extremely clear and low waters; especially in the 1960s, 70s and early 1980s when we seemed to have colder and drier periods of weather in the winter. Guess what I found the fish in exactly the same places as I find summer fish under similar flow conditions - they are where they are comfortable.

I found the fish "hidding" in the riffles in the winter in 38 degree water and in the summer in 68 degree water. The common factor was the cover that the broken surface provide not oxygen or temperature. In virtually every case the fish are in the soft pockets (behind boulders, drop-offs, ledges etc) within the faster water.

There comfort is based on a need for safety (hidden from sight) which places them in the shadows, under log jams, in the faster water etc. The other aspect is temperature - often will find fish in the deep pools holding in the very slow water. As in the summer they aren't in all pools but tend to concentrate in those with gorund water seeps. On a give section of river in very warm water or very cold water you find the fish in the same pools. The ground water provides a moderating effect on the stream temperature (cooler in the summer and warmer in the winter). This can be critical in the more northern waters as the gound water seeps provide protection from anchor ice.

Just for thought - perhaps the fish act more "frisky" when released in faster water because they have to been. In that type of water they don't have as wide of choice of actions as they would in a more moderate situation.

How many photos does one need in one's album? When fishing in marginal conditions why subject the fish to even a few more seconds of handling needed for a photo - even if it isn't rmoved form the water? It seems to me for many this need to photography every fish is the same reason in past that many anglers "bonk" fish and took them home to be given away. - The need to brag or show off ones fishing powers! I enjoy a nice photo as much as the next guy but is there really a need to photograph every fish, especially when the fish has been stressed?

Tight lines

08-07-2003, 02:15 PM

You are right on on the photo shoots. Why must we insist on taking pics of 5 to 8 pound steelhead. Not against a picture or two in the right situation or if it's a first fish or one that is special to the fisherman but most just end up in a desk draw. I'm guilty as a lot are but will change my ways. Hope the rest of you who take lots of fish pics will consider what Smalama brought up.

Also agree cover is high on the instinct list to a steelhead that's sole intention is to survive in its home river and spawn.

We need to look continuouslly at our own self and why we call ourselves sport/ fly fishers. At the end of each day on the river we need to take a little time and ask ourselves did I truthfully put the fish first. Was that my intention and did I succeed. If we do I think that the warm water thing, fighting fish under extreame stress, photo shoots, light gear and few native fish will find the a right answer for each and everyone of us but you got to ask the questions.

Now is the time to enjoy catching hatchery salmon in the salt and enjoy not only the sport but that they taste oh so good too.
Fishing in the next two months is a great time to be outdoors in the North West a reward for so many wet cold days we put in the rest of the year.

08-07-2003, 03:17 PM
We need to look continuouslly at our own self and why we call ourselves sport/ fly fishers. At the end of each day on the river we need to take a little time and ask ourselves did I truthfully put the fish first. Was that my intention and did I succeed. If we do I think that the warm water thing, fighting fish under extreame stress, photo shoots, light gear and few native fish will find the a right answer for each and everyone of us but you got to ask the questions.

OC This is the point I was trying to make in my original post when this thread started. That I would much prefer, instead on relying on a governmental agency to make more rules, ( in essence act as our conscience) we as sportsmen should be taking personal responsibility for not doing anything that damages the resource. You said it better than I. Take care, MJC

08-07-2003, 11:27 PM
Speaking of photos and such...I sent through a proposal that would not allow wild steelhead to be fully released from the water if they are to be released...hopefully it gets somewhere.

Also speaking of photos...do not get me started on how I often I see piss poor photos taken where the angler and photographer are more concerned with how the shot comes out then the fish.

08-08-2003, 11:00 AM
1 quote for all the picture takers.........................

Many go fishing all their lives without knowing that it is not fish they are after.
- Henry David Thoreau

Rick J
08-08-2003, 02:44 PM
Your statement that riffles do not have more oxygen ain't so. A common method of introducing oxygen into water is to run it over shallow broken bottom - this puts more of the water in contact with the atmosphere and allows maximum oxygen uptake . It is true if water is the same temperature, it's maximum capacity to hold oxygen is the same but in slow deep pools oxygen can get used up so it is possible that this water may not be holding maximum amounts. That is not to say that a major reason the fish are in the riffles are for cover and not due to oxygen.

08-08-2003, 08:49 PM
awright, a discussion of dissolved oxygen!!!

In cool northern latitude streams - many of our steelhead rivers - riffles and pools can have equal amounts of oxygen. As water warms, decomposition of organic matter accelerates and can deplete dissolved oxygen in slow moving areas.

With equal amounts of dissolved oxygen in pool and riffle areas, fish get more oxygen in a riffle because there is more water passing over the gills - a conveyor belt effect

The only way to supersaturate natural waters with oxygen - to have oxygen at levels higher than predicted from chemical equilibrium - is by photosynthesis. This sort of thing leads to marl formation in lakes, etc etc.

In a previous life I was a student of these sorts of things..

Rick J
08-08-2003, 11:02 PM
In my response I did not indicate that riffle water would become supersaturated. But as you indicated in long sections of slow moving water (frog water) a depletion of oxygen can occur. When this oxygen deprived water hits a shallow riffle it can take up oxygen to more normal levels.

I am a student in this life being an engineer who has designed water treatment facilities.

08-09-2003, 12:16 AM
Rick -

no matter about the supersaturation - I only mentioned it because it is common thinking that waterfalls and the like are capable of increasing oxygen to greater than average levels. but this isn't so - its dictated by simple temperature and partial pressure stuff

08-09-2003, 12:20 PM
Rick -
I did not mean to imply that riffles do not oxygenate water - obviously they do. What I said was "surface dissolved oxygen levels in the riffles and pools are typically the nearly the same". While the water may become oxygenated in the riffles it will be only at saturation or below. Once the water flows from the riffle the oxygen levels in the pools will remain the same unless it warms appreciately or there is some sort of large biological oxygen demand (BOD). Normally in most of our PNW streams there are not enough critters or decaying organic materail to significantly reduce the oxygen levels of the water.

Loco -
I don't think your theory that in riffles there is more water flowing over the gills of the fish holds water. For increased water to be flow over the fish and through its gills the fish would have be to actively swimming to holds its place. That is not the case. While snorkelling riffles/whitewater areas the adult steelhead that I have observed are typcially calmly holding a position with virtually no effort. At times one will see them even with there heads or even the whole fish tucked into the cavities in and around large boulders. Due to the coarseness of the stream bottom of most riffles there are plenty of low/no velocity holding areas. While surface current speed may be quite fast the fish's holding areas are quite calm. This phenomenon of calm water associated with coarse stream bottom is why those areas with large substrates are better holding areas/fishing spots? than those riffles flowing over pea-gravels or small stones.

While I'm not an aquatic chemist or hydrologist my ideas and theories are based on my limited training and experiences. They seem to fit what I see on the water and have allowed me to more often correctly perdict where the fish are and what they are doing (read the water?) and thought that they might be of interest and helpful to some.

Tight lines