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Location: SE Wisconsin | There's a lot of great minds on this forum and plenty with solid knowledge on the effects, both positive and negative, that Disolved Oxygen (DO) can have on our favorite quarry. I think what seperates consistency from luck on the water is the dynamic approach consistent sticks use to identify where to fish and with what. I learned a long time ago that after the photo, release and high-fives, good medicine is to reflect on the success and consider the "why's" behind your catch. This topic should be another gun in the holster if we can get some solid insights, so let's get the ball rolling...
DO comes from tiny bubbles in the water too small to see from the human eye, but their importance is the factor between life and the dead sea when it comes to fish, kind of similar to the difference between humans breathing fresh air and smog in the city. Rain and wind are a majore contributor in creating these little bubbles when they churn the surface, thus the surface of most lakes tend to have higher concentrations of DO than deeper, colder water - bring on the Thermocline Discussion and how fish use it!
Colder water... Temperatures do play a factor in DO, where colder water will generally contain higher concentrations of oxygen than warmer water because the warmth excites the molecules and tends to disperse the oxygen bubbles like bizerk masquitos. Another thing I've learned along the way is where you find a lot of algae you'll also find low DO levels because the algae basically uses it up; conversely, I avoid sheltered bays in the summer and I believe it saves me time. There's a whole bunch more factors that go into increased/decreased oxygen levels but I'll let someone else divulge those instances..
I asked a question back in college on the topic; Are there ever instances when there is too high of a concentration of oxygen for fish and the answer was that over-consumption of DO levels will drown a fish, not the water... Case and point, determine the areas where DO can be very low by understanding the determinants and you can eliminate a spot or two, but remember, this isn't generally going to be a daily determinant, but more of a seasonal or situational determinant.
One thing I always try to remember is to think about forage first, then relate to musky. If the bait isn't there, chances are the musky aren't either.. certain species of fish (cisco) need certain amounts of DO to be comfortable, and keying in on these details can tell a good story. All I'm saying is don't always relate DO to what's comfortable to a musky, thing of the little things they eat, too. I DO know that at times musky will sacrifice comfort for a good meal, so sometimes certain prey that thrive in low DO conditions may look tasty to musky 
Edited by Sam Ubl 3/15/2011 4:31 PM
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Location: Minnesota: where it's tough to be a sportsfan! | On the other hand commercial fish transports utilize Gas Packs of cryo-genic oxygen and will be sending 4LMP of 98% pure O2 into the water the fish are in like 4x4 cells with the water approx 4 foot deep or so. These fish are often in this environment for 48 hours or longer. When they arrive they look extrememly healthy and are super active.
Intersting enough the amount of dissolved oxygen in the water is in direct relation to the water temperature. Colder water holds more O2 up to 39.1 degrees. | |
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Location: Oconto Falls, WI | Sam, as the answer to too much DO level would drown a fish, was there a number thrown out? I doubt a fish in it's natural state will sit too long in DO levels too high for themselves and thus commit suicide. I would think they do the same thing as areas with low DO levels, and that is go in for just short periods of time.
Does a fish 20' down know that because it is raining that the DO level near the surface could be higher then where they are at, and thus rise up in the column? I doubt it. IO kind of look at it like this. Take the water temp theory in the spring. Do fish in the south end of the lake know that the north end is suppose to be warmer, and thus either need to be there to eat, or shouldn't be eating where they are at? Nope!
I honestly don't know what to think about DO levels themselves in that does a fish actually seek out a certain DO level if the whole water column has sufficient amounts of it? I would tend to believe the fish seek out their preferred water temp first and foremost, and get whatever DO level is there. I think chasing DO levels at all is like chasing the pot of gold at the end of the rainbow.
Clear water systems can have DO levels well below the thermocline (lots in northern WI do) and thus the thermocline is nothing other than a temp barrier if you will. If those lakes have forage that love it deep (whitefish for example) it don't matter if you have a thermo or not as there will be some fish way down there chowing on those whitefish or other forage. | |
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Location: Grand Rapids, MI | Travis, are you saying that in the dead of summer when there is a distict thermocline at the 25' level, that there could potentially be muskies deeper than that? That would be something that contradicts what I've learned.... (which is that there is not enough oxygen below the thermocline to support them) | |
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Location: Oconto Falls, WI | That is exactly what I am saying!
Some of what comes into play with DO levels below the thermocline is a relationship to how fertile the water is, and what is has for weeds. It is the decaying matter at the bottom of a lake that reduces the DO levels as well as water clarity, and how far sunlight can penetrate. The less matter you have decaying the better possibility you will have higher DO levels below a thermocline.
Take a look at the following picture which shows temp, and DO levels. I would say there is sufficient DO levels below the thermocline. Look at the 7/18 date specifically. Thermo is between 25’ and 30’ judging by the temp drop.
The data below willalso show you that depending on the day the amount of DO available can vary at depths.
Edited by CiscoKid 3/18/2011 7:25 AM
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 DO Level.jpg (82KB - 170 downloads)
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Location: Oconto Falls, WI | Lots of info out there on DO, but I found this one interesting as it puts some numbers to fish.
http://www.water-research.net/Watershed/dissolvedoxygen.htm
Also keep in mind as something the above link mentioned. The warmer the water the more DO a fish will need, and conversely the lower the water temp the less DO a fish will need. | |
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Location: Minnesota: where it's tough to be a sportsfan! | I have found on the water in the fall where fish believed to be Muskie by the hooks are below the existing thermocline. The thermo was very distinct. Since I have only found this 3 times and for short periods of time ( 2-3 days tops) my take was that there is a large amount of dead or dying baitfish in the thermo layer offering a buffet of sorts to the larger fish. The fish were deep enought that I did not want to bring one up from that depth and just kept going back and looking at them from time to time. This was just prior to turnover period. The last time I pulled out my old X-16 paper graph and took good long printouts over the whole area. The hooks are huge in comparison to the smaller hooks in suspension. | |
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| jakejusa - 3/18/2011 9:36 AM
I have found on the water in the fall where fish believed to be Muskie by the hooks are below the existing thermocline. The thermo was very distinct. Since I have only found this 3 times and for short periods of time ( 2-3 days tops) my take was that there is a large amount of dead or dying baitfish in the thermo layer offering a buffet of sorts to the larger fish. The fish were deep enought that I did not want to bring one up from that depth and just kept going back and looking at them from time to time. This was just prior to turnover period. The last time I pulled out my old X-16 paper graph and took good long printouts over the whole area. The hooks are huge in comparison to the smaller hooks in suspension. WHAT??? | |
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Location: Rhinelander, Wisconsin | Something to consider:
There are two distinct types of thermoclines at play here. Single story, and two story, to oversimplify. In the single story situation, when a thermocline sets up there is frequently not enough oxygen below the thermocline to support fish, making it pretty easy to eliminate that portion of the water column when looking for game fish. Deeper waters might support a two story set up, as is seen in trout waters. The thermocline there is temperature identified more than oxygen level identified, and trout and salmon will frequent the cooler waters below the thermocline. | |
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Location: Oconto Falls, WI | sworrall - 3/18/2011 11:19 AM
Something to consider:
There are two distinct types of thermoclines at play here. Single story, and two story, to oversimplify. In the single story situation, when a thermocline sets up there is frequently not enough oxygen below the thermocline to support fish, making it pretty easy to eliminate that portion of the water column when looking for game fish. Deeper waters might support a two story set up, as is seen in trout waters. The thermocline there is temperature identified more than oxygen level identified, and trout and salmon will frequent the cooler waters below the thermocline.
Thanks Steve for clarifying what I was really trying to get at. Sometimes it is clear in your head, but unclear when typed out for someone else.
Most people almost always just think of the one story type, but I am sure it is associated with the type of water they fish. I usually think of the two story type as that is the water I fish. | |
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| sworrall - 3/18/2011 11:19 AM
Something to consider:
There are two distinct types of thermoclines at play here. Single story, and two story, to oversimplify. In the single story situation, when a thermocline sets up there is frequently not enough oxygen below the thermocline to support fish, making it pretty easy to eliminate that portion of the water column when looking for game fish. Deeper waters might support a two story set up, as is seen in trout waters. The thermocline there is temperature identified more than oxygen level identified, and trout and salmon will frequent the cooler waters below the thermocline. Sworrall, I think you mean to say there are two distinct types of FISHERIES at play here. Uhm.......it is after all a THERMOCLINE they are talking about, and the THERMOCLINE is always TEMPERATURE identified. Geez, I guess because it is a THERMOcline...;) . | |
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| Here's a simple description of lake stratification, along with some cool illustrations:
http://faculty.gvsu.edu/videticp/stratification.htm | |
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Location: Warroad, Mn | Dissolved O2 is very important to fish. However, fish don't seek optimums! If the O2 level is within the range of survival for both them and their forage they are happy where they are. They also don't have any sort of communication system that tells them that the O2 levels (or any other factor that we think is important) are better on one side of the lake than the other. In general I doubt that there's very few muskie lakes that will have an Oxygen problem or there wouldn't be muskies in the lake. It's also very hard for most anglers to measure the O2 levels, and if they could I'll bet that most of the time it wouldn't tell them anything useful (much like PH). I doubt that there's anyway to get too much Oxygen in any fresh water lake. I'll bet that your professor who told you that you can "drown" a fish with too much oxygen was talking about exposing the fish to air not O2 in the water. In general even in two story lakes muskie won't be found below the thermocline, just because of water temperatures (they are warm water fish). Most Ontario trout water that have muskies are two story, (Oxygen below the thremocline) most muskies (not all) are still found in the warm water part of the lake. I might also add the algae is a plant and produces Oxygen through photosynthesis during the daylight hours rather than using it up. Doug Johnson | |
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Muskies don't seem to have a problem being in very shallow water in the heat of the summer when the 02 levels are at the lowest point of the year. Just look at them on the warm water sand flats of Mille Lacs, the rushes on Leech and rockpiles on Vermillion or LOW.
If you measure 02 levels below a thermocline in most lakes they are not so low that fish can't survive. Like DJ said they prefer the wamer water and tend to use the higher warmer column.
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Location: Rhinelander, Wisconsin | Depends on the water-body entirely. Some of he lakes I fish stratify quickly, and the amount of dissolved oxygen is so low below the thermocline live bait that lives a long time above will die immediately below. There's no fish below the thermocline at all, and the 'eyes and perch stack up on the rock spurs and piles that are just above that level predictably, if you know what to look for, and those same small spots can be magic for muskies as well.
http://www.michiganlakes.msue.msu.edu/MichiganLakes/LakeEcology/Dis...
I've even seen this situation in late meso waters.
Learn all you can about thermoclines and what they look like on the new sonars, and apply that knowledge to all the lakes you fish. Some will never stratify, some do very quickly, and some move in and out due to prevailing winds and storms, etc.
Muskies will generally be above the thermocline if you can see it clearly on the sonar and you are looking at a one story system. If the water is reasonably clear, considerable numbers of forage fishes may concentrate on the structures just above, and where there's food.. | |
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| Can someone explain how O2 content and water temps differ in a "2 story fishery"? I'm not sure I understand exactly what that is.
And would catching muskies from those depths below the thermocline in exceptionally warm water potentially be fatal? (to them, not me!)
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| http://faculty.gvsu.edu/videticp/stratification.htm
Go to illustration 3 of your own diagrams.
In a one story fishery, the light blue water is the only water which will contain significant amounts of oxygen. I think musky need something like 5 parts, could be lower or higher(rought estimate). In a one story fishery ie Cave Run Lake, KY, the water below the thermocline actually gets so low in dissolved oxygen it would kill a musky. And it does get very low something below 1ppm. It is essentially a dead zone for aerobic life. Happens down here every summer.
In a two story fishery ie Laurel Lake, a short trip from my house, you get the same two layers of water stratification in the summer with a thermocline in between. However, Laurel Lake, unlike Cave Run has a depth of 60-140 feet over much of its area, and is also fed from a very pristine, and somewhat sterile, wooded watershed. Low fertility in the lake, clear water, nothing using up oxygen, so in this lake's TWO STORY FISHERY, the water below the thermocline, the dark blue area, has high dissolved oxygen content, which makes it very suitable for the 100,000 rainbow trout they dump in every year. I would guess but am not positive that the reason all one story lakes are one story, is that they have too much organic content deteriorating(using up oxygen while doing so) beneath the thermocline, and since the water is no longer mixing with the surface and the air, the depleted oxygen levels never recover until turnover starts the mixing process again.
READ PLEASE, I was not smart enough to get a direct address, click on RAW DATA at the top of the page to get to the actual data profile, and that put you on the page.
http://www.lrl.usace.army.mil/wc/wq/crr.html
Here is a profile of depth temp and oxygen levels for Cave Run in October 2010, you can note clearly the thermocline occuring between 45 and 50 feet, and sliding over to the oxygen levels, you see it drop from 6 to 0.1, and thus the dead zone. If you were to watch this chart through the summer, the thermocline actually comes up to 25 feet. The thermocline in late October is from the deepwater basin, and is not far from turning over. In the summer you will see much higher temps in the upper water column.
Edited by firstsixfeet 3/19/2011 6:14 AM
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Location: Oconto Falls, WI | firstsixfeet - 3/19/2011 6:06 AM
READ PLEASE, I was not smart enough to get a direct address, click on RAW DATA at the top of the page to get to the actual data profile, and that put you on the page.
http://www.lrl.usace.army.mil/wc/wq/crr.html
Here is a profile of depth temp and oxygen levels for Cave Run in October 2010, you can note clearly the thermocline occuring between 45 and 50 feet, and sliding over to the oxygen levels, you see it drop from 6 to 0.1, and thus the dead zone. If you were to watch this chart through the summer, the thermocline actually comes up to 25 feet. The thermocline in late October is from the deepwater basin, and is not far from turning over. In the summer you will see much higher temps in the upper water column.
I could be wrong, but I wouldn't consider that a thermocline. There should be a greater temp difference than that I would think, but like I said I may be wrong. Look at the last profile of depth, temp, and DO in my previouse post. Clearly it indicates a thermocline between 30' and 40'. The July profile, as I mentioned earlier as well, clearly shows a thermo between 25' and 30'. This one also shows more than enough DO below thermo. The last profile (sept) does show typically of what people think about DO below thermo even though the reading below thermo does have enough DO (barely) for fish. After that the DO drops drastically. | |
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Location: Oconto Falls, WI | Guest - 3/18/2011 9:37 PM
Muskies don't seem to have a problem being in very shallow water in the heat of the summer when the 02 levels are at the lowest point of the year. Just look at them on the warm water sand flats of Mille Lacs, the rushes on Leech and rockpiles on Vermillion or LOW.
If you measure 02 levels below a thermocline in most lakes they are not so low that fish can't survive. Like DJ said they prefer the wamer water and tend to use the higher warmer column.
Who is to say the DO is low in the shallow water in the heat of the summer? Have you checked? Is it calm when the fish are found way up in the skinny water, or windy? Certain there are no springs?
Fish going skinny is not the case in all lakes, and the whole population within a lake. There are lakes that ALOT of fish will sit down in the cold water with the cold water forage. Lots of tasty whitefish and laketrout can be convincing for big fat girls to hang around. Sure on special occasions those same muskies may be found up in shallow water (maybe digesting, maybe not), but their home is deep. Just my opinion but deep water fish are a different breed, and their preferred water temp may just be a tad different than other fish. I don't think there is a hard line on what ALL muskies like or dislike. I am sure there is a varience amongst the whole population. Same is why some fish are shallow most of there lives, and some or nomads and spend there lives in deep water most of the time. I even believe Doug J has referenced these fish something like the silver giants (or something like that) that he only sees in the fall on LOTW. Doug can correct me if I am wrong.
Edited by CiscoKid 3/19/2011 5:29 PM
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| CiscoKid - 3/19/2011 5:19 PM
I could be wrong, but I wouldn't consider that a thermocline. There should be a greater temp difference than that I would think, but like I said I may be wrong. Look at the last profile of depth, temp, and DO in my previouse post. Clearly it indicates a thermocline between 30' and 40'. The July profile, as I mentioned earlier as well, clearly shows a thermo between 25' and 30'. This one also shows more than enough DO below thermo. The last profile (sept) does show typically of what people think about DO below thermo even though the reading below thermo does have enough DO (barely) for fish. After that the DO drops drastically.
Sorry you think it should be different, but check the graph again, there is a 3.5 degree temp drop over 5 feet. That is what is left of the thermocline. The oxygen levels above and below are also notable, in that there is no mixing going on, and it is still stratified. Check above this and you will find a 1.7 degree drop in 45 feet. Check below and you will see a 3.6 degree drop in 20 feet. rapid temperature change per foot of drop identifies the thermocline clearly. Check the same graph in summer and you will see it much higher and much more clearly, but it is what it is. | |
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Yah, actually I have checked DO in shallow water and in most cases it is at a lower level than in the deeper realms, which makes perfect sense as the warmer water gets the less ability it has to hold O2.
Wind can help mix water with O2 but the limiting factor of how much O2 can be present is water temp when you are in the shallows. Doesn't matter how much wind you have the level can only get so high.
Muskies can tolerate much lower levels of O2 than say ciscoes or trout can, hence the preference of suspending in cooler depths by those fish in summer. Cooler water holds more O2.
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Location: SE Wisconsin | CiscoKid - 3/17/2011 8:00 PM Sam, as the answer to too much DO level would drown a fish, was there a number thrown out?
I'm glad this thread is growing, good info so far.
The idea that fish could drown of an over dose of DO was just a little tid-bit to toss in, no number thrown out.
I would agree, a muskie in 20' wouldn't know that there is more DO at the surface after a rain, but I am certain that DO sensitive fish will at times, like cisco and trout. Follow the food chain.
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Location: Green Bay, WI | Yes, neat thread...very educational. I am studying some of the links, and found that "Seasonal Lake Stratification" link to be excellent. Limnology was a long time ago for me, so I was happy to get the review.
I remember the chemistry of dissolved oxygen a bit differently than Sam mentioned though. I don't remember there being any tiny air bubbles involved. Rather the oxygen molecules are chemically-bound to the water molecules. But I can't remember whether of not it's a simple hydrogen bond that is responsible, or if it's something more like a Van der Waals force.
But it's nice trip down memory lane, this thread. Very cool! | |
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Air bubbles would be undissolved O2.
JS | |
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Location: Green Bay, WI | That's pretty much what I was thinking, but stated in a "politically correct" fashion... | |
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Location: Minneapolis, MN | Does anyone know how a spring changes stratification, or does it have no effect? Does a spring bring O2 into the system, and if so, in enough quantity to provide a little refuge in an otherwise dead sea? | |
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Location: Oconto Falls, WI | stinger - 4/2/2011 7:45 AM
Does anyone know how a spring changes stratification, or does it have no effect? Does a spring bring O2 into the system, and if so, in enough quantity to provide a little refuge in an otherwise dead sea?
Yes, yes, and yes. | |
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Location: Green Bay, WI | stinger - 4/2/2011 7:45 AM
Does anyone know how a spring changes stratification, or does it have no effect? Does a spring bring O2 into the system, and if so, in enough quantity to provide a little refuge in an otherwise dead sea?
Well, I would think that it would take a couple of weeks or more to replenish dissolved oxygen in the system, once the ice goes out. In the Winter, the warmest water tends to be at the bottom of the water column, due to the fact that its density is greatest at about 4 degree Celsius, and water at the surface is obviously colder given its proximity to the ice. So once the ice melts, the stratification process starts all over again. Check out this link for a very nice visual:
http://faculty.gvsu.edu/videticp/stratification.htm
Because the water (in Spring) is of nearly uniform temperature from the surface to the bottom, there is no appreciable temperature-based stratification. So the water is free to mix, as shown in that series of graphics. Nutrients from the bottom are mixed throughout the water column, providing food for the various types of micro-organisms. These then grow, and a new life cycle begins. As the water warms with the increasing sun energy applied to the system, it starts to stratify once again.
TB
Edit: I forgot to add that since water has such a high specific heat index, it takes quite a while for there to be a significant change in temperature when heat is applied to the system. That's why it takes a while for the thermocline to develop, and for the lakes to turn over in the Fall. That's also why climatic changes aren't as abrupt/drastic near large bodies of water.
Edited by tcbetka 4/2/2011 10:04 AM
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Location: Oconto Falls, WI | Tom I think the spring he speaks of is not the seasonal type, but rather the kind that bubbles out of the ground.
Good thoughts about water temp, and the water in the springtime.
Edited by CiscoKid 4/2/2011 10:58 AM
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Location: Green Bay, WI | Oh...LMAO!
"Springs"
Gotcha.
TB | |
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Location: Minneapolis, MN | Yep, bubble out of ground type. | |
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