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Posts: 119
| Just wondering what y'alls thoughts are about good indicators of musky fatigue. Obviously how the fish acts after air exposure is the most important, however, my boat partner and long time musky angler swears up and down by the reddening of the fins as his indicator. I can't prove him wrong on his theory. We CPR as fast as possible to reduce fatigue at any rate but just wondering if there is any merit to his claims or its an old timers tale.
-Riv |
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Posts: 735
Location: Apparently where the Muskie aren't | I believe it is somewhat true. Bass (specifically smallmouth) get very colored up and get red eyes when they are stressed or excited. I have a smallmouth in a aquarium and when he's just sitting there he is pale or at least his colors aren't very vivid. But when it's feeding time his colors become very vivid, and he gets red eyes. This same thing happens when you take a smallmouth out of the water. |
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Location: Green Bay, WI | I've never read anything specific in the literature (in terms of changes indicative of fatigue in fish), but I would think it would be very similar to the pinkness of the capillary beds in humans.
In human medicine, we use the "pinkness" of the capillary bed as a rough indicator of the level of perfusion of the tissues. Just pinch your finger at the nail, and you'll see what I mean: The color goes to white when you apply pressure, and then back to pink when the pressure is released. In a healthy individual that should happen within 2-3 seconds or so, give or take a second. In someone who is volume depleted or otherwise in significant "stress," it's delayed...often significantly so. Fish probably aren't as likely as humans to be volume depleted--as humans might not replenish fluids fast enough after sweating a lot (hot days), or might have a lot of fluid loss through something like vomiting and/or diarrhea when ill. But in theory it would be possible for fish to be volume depleted; especially saltwater fish. This is less likely for freshwater fish however as they are always absorbing water from their environment through their gut, and across their skin via osmosis, because their blood is hypertonic (salty) compared to the water they are swimming in. Saltwater fish have to drink water as they continuously lose water to their environment, so theoretically it should be much more likely to see a dehydrated saltwater fish than a freshwater one.
Therefore it would seem (to me anyway) that any abnormalities in coloration of a fish post-catch are more likely to be caused by vasomotor activity, instead of some underlying medical condition like dehydration or "hypovolemia." Perhaps their autonomic nervous system has an abnormal response to the stress event of the catch, thus rendering the fish less likely to perfuse its tissues normally? I'm not sure how you'd ever quantify something like this however, as you would have to monitor blood pressure to know for sure--as it's the tone of the vessels (ie; the degree of vessel constriction), along with blood volume, that ultimately determines pressure. In humans, we have this relationship:
BP = CO * SVR
Where: BP = Blood Pressure; CO = Cardiac Output (heart rate times stroke volume); SVR = Systemic Vascular Resistance, or "tone" of the vessels. Thus:
Assuming that the same basic relationship holds true in fish, and assuming that the fish's blood volume doesn't drop significantly due to blood loss from the catch/unhooking, then it would seem to make sense that the vascular tone is likely the determining factor of their BP in most cases. Obviously if they bleed a lot following hook removal, we shouldn't be surprised if they exhibit signs of significant stress after the catch. But in the absence of significant blood loss, anything that has a significant impact on their overall vascular tone will likely play a major role in determining how well they'll react to the stress of the catch event.
Finally, keep in mind that in humans, some people react much more severely to a given event than others do. Consider the process of fainting--it's called a "vasovagal response" in human medicine. Some people, when exposed to a certain stressful stimulus, react by having a massive degree of vasodilation...which leads to a significant decrease in their blood pressure...which leads to them fainting when in the upright position. Since fish don't stand up, the effects of gravity aren't likely as significant as in humans--but it certainly plays some role. And it is extremely likely that some fish simply aren't as capable as others are, when it comes to normalizing their physiology after being caught. Maybe they are older, ill, injured, or whatever, and thus have a higher level of baseline stress to start with. So one could postulate that this may be why a fish is unable to maintain itself in an upright position in the first few minutes after the catch: They may simply be showing signs of having an abnormal vasomotor response to the catch.
By the way...any redness in the eyes, fin bases (or anywhere else where vessels are close to the skin surface) MUST be caused by blood flow to that area. There's really nothing else that could be causing redness in an animal with blood. So if you observe this abnormal coloration it's a good bet that they are in significant stress, and that an abnormal underlying neurological response in their autonomic nervous system is the culprit. And I would not be at all surprised to see that these fish also have problems maintaining an upright position.
Sorry for the doctor-speak, but it's the only way I know to begin to explain the physiology that I believe to be in play here.
TB
Edited by tcbetka 6/27/2017 9:09 PM
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Posts: 119
| Well that is one heck of an explanation TC .... and while it took me a few passes to fully understand your post I can agree with some of your facts and hypotheses. When it comes to musky fishing the age old addage that I always hear is the oxygen level of either the water or the fish. So while I agree with you in your statement about a freshwater fish being dehydrated is an unlikely culprit, I am in the camp that it has something to do with stress levels and the amount of energy is exerted during the fight which translates into how much oxygen is left in the fish's blood stream after a fight, the unhooking process and air exposure (if any). I am just wondering if the reddening of the fins has something to do with the fatigue of the fight or if it is more the stress on the fins themselves from the energy exerted by the opposing forces both the fish and the angler. I've seen some fins actually bleed a bit so I'm not sure if they are related or they are separate issues that causes the fins to redden. |
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Location: Green Bay, WI | The fish doesn't have a supply of oxygen dissolved in the blood that gets used up. It doesn't work like that. While there may be a slight amount of oxygen gas in the blood, it is not really bioavailable to the tissues. Certainly there might be some of that going on, but the majority of oxygen is bound to the hemoglobin molecule inside of the red blood cells (RBCs). As long as the fish has a relative normal volume of RBCs, and has the ability to increase its heart rate in response to an increased oxygen demand, then they'll oxygenate the tissues. It's no different than in humans, under ideal conditions. The real determinant, which you mentioned, is the level of dissolved oxygen in the water.
Since fish cannot "breath" air, they must rely on only the oxygen dissolved (DO) in the water for any significant respiration. They tend to do better in cold water because there is more DO available. When water is colder, the molecules have less energy and thus are better able to bind oxygen molecules. Warm the water and the H2O molecules have more energy, and fewer H2O-O2 bonds remain...so the water cannot "dissolve" as much oxygen. It's pretty simple actually. But the gist is that fish can better tolerate stress in cold than in warm water, because they are better able to respire.
It's sort of analogous to humans out running on a dry cold day in the fall, versus a hot humid day in the summer. The hot summer air holds more water for the same reason as above, and because there's more water vapor present in each breath you take...you get less oxygen. Therefore you're likely to be more short of breath while running on a hot summer day compared to running on a cool dry day in the fall. So now, if I were to come along on both days and chase you with my car...on which day would you be better able to elude me?
TB
EDIT: I should add that I have read one or two papers in the scientific literature that (from memory) postulated that the incidence of cardiac arrhythmias increased under conditions of lower DO levels, and this lead to an increased post-catch mortality in the angled fish. While there weren't a lot of musky-related studies in this area as I recall (the Nogies Creek study may have been one), there were a couple nice papers in the literature on cardiac-related causes of post-catch mortality in fishes. Maybe there are more musky-specific papers now, but I haven't researched in a few years. Sean Landsman might know better than I as he finished his Masters degree not all that long ago.
Edited by tcbetka 6/25/2017 6:51 PM
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Posts: 119
| So are suggesting that the increased heart rate from the fight, ect ... raises the blood pressure of the fish and is the reason behind the reddening of the fins ? |
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Location: Green Bay, WI | River2Stream - 6/25/2017 6:49 PM
So are suggesting that the increased heart rate from the fight, ect ... raises the blood pressure of the fish and is the reason behind the reddening of the fins ?
That's possible I suppose, but I don't think it's all that likely because many fish don't display those types of stress-related changes being discussed in this thread.
I was thinking more along the lines that in fish predisposed to an abnormal reaction to angling-related stress, their autonomic ("automatic") nervous system is causing the visible changes you're describing. I have no proof of this, but it's almost certain that this reddening in certain tissues is related to blood flow--basically, like the flushing of human skin. That's mostly related to vascular tone, which is largely controlled by the autonomous nervous system. Certainly the blood pressure of the fish goes up under stress--it has to, based on the equation I posted in my earlier post.
BP = CO * SVR
And given, CO = Stroke Volume (SV) times Heart Rate (HR)...
BP = SV * HR * Vascular Resistance
So then you can see that anytime the heart rate goes up, so does blood pressure. It's a normal physiological process--and there's nothing we can really do about it. But it IS more of a load on the heart of course, since the heart is the pump that's generating the output to meet the increased oxygen demand imposed by exercising muscles.
It's simple physics for the most part. But this happens with any reaction to stress...and one could argue that most caught fish are likely under increased stress due to their struggle to free themselves. Yet we don't see the reddened changes in the vast majority of caught fish. Why not?
TB
Edited by tcbetka 6/25/2017 7:08 PM
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Location: Green Bay, WI | I should add Riv, that although humans really don't use much of the oxygen dissolved in their blood plasma (fluid), that plasma has a HUGE carrying capacity. In fact, when I practiced Hyperbaric Medicine, we used this carrying capacity all the time.
By putting someone in a Hyperbaric Oxygen (HBO) chamber we can give them 100% oxygen at hyperbaric pressures--that is, over 1.4 atmospheres. When you consider that humans breath air that's about 21% oxygen, and they are most often not at sea level pressure, we really don't get a whole lot of oxygen. But it's enough, because our heart rate can go up in response to a physiological challenge. But give someone 100% oxygen at 2-3 atmospheres of pressure, and I think you can see that the amount of oxygen they get is tremendously higher. In fact it's toxic at that level for prolonged periods, and can cause seizures, fibrosis of the lungs, and even cataracts. But the point is that since the hemoglobin molecules in our red blood cells are nearly 100% saturated with oxygen under normal conditions anyway, we can't really use the red cells for oxygen delivery in the HBO chamber. Instead we use the plasma like an oxygen sponge. Saturate the heck out of it, and it will carry oxygen anywhere in the body that can get blood flow and that oxygen will "leach out" of the blood into the tissue, down the pressure gradient. Good stuff Maynard!
It's more complicated than that, but I'll leave that for another discussion. But I believe that's roughly the principle behind these products that you can add to your livewell to increase the amount of dissolved oxygen--they are attempting to super-saturate the blood with oxygen. However unless you can drive the oxygen into the plasma under pressure, it just doesn't work all that well. In HBO medicine, you just don't see the benefit(s) of the extra oxygen unless you can drive it into the blood with increased pressure. Hence the "hyperbaric" nature of HBO therapy.
TB
Edited by tcbetka 6/25/2017 7:27 PM
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Posts: 343
| I have a question; I've seen muskies porpoising early in the morning with red caudal and paired fins, why would that be the case? |
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Location: Green Bay, WI | I'm just guessing, but I'd think that the red areas would be very well-perfused with oxygen-rich blood. But whether the porpoising behavior is related to the reddened fins would be tough to answer. Maybe they're having an oxygen "high" and are happy?
A well-oxygenated musky is a happy musky!
TB |
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