|
|
Location: Grand Rapids, MI | tcbetka - 11/22/2017 12:32 PM
So this tells me that while the fish's overall metabolism is likely diminished in the fall due to falling water temperatures, the rate of digestion likely isn't.
Could they be crapping all over your boat because the rate of digestion had slowed so much that they're eating beyond their digestive rate? Late fall muskie poop is very different from summer muskie poop and appears to be less digested (more scales, bones, etc). |
|
| |
|
Location: Green Bay, WI | I suppose it's possible, but generally speaking the gastrocolic reflex dictates...in with the new, out with the old. So that means that if there's food in the stomach, there's poop in the bowel--and it's heading for the great outdoors. That said, the fish aren't always pooping *voluntarily* mind you. Some of it is pressure from angling and some of it is certainly from their autonomic nervous system stimulus, related to the catch.
The other thing is that I really don't know how any animal is going to out-eat their rate of digestion. They would be satiated to the point of not wanting to eat any longer, simply because (I'd think) they wouldn't be able to physically get any more food into their stomach. Then again my dog seems to ALWAYS want to eat, even when she's just eaten. But I think that's more of a psychological thing--as you saw that night we were eating pizza while watching the football game.
So I tend to think that although the fish may indeed have a somewhat slowed rate of metabolism, it isn't nearly as significant as we might think. Don't forget that we anglers tend to think of warm water temperatures in the summer because the surface temperatures exceed 70 degrees. But in all reality the fish are going to seek out water temperatures most desirable to them...which means finding deeper/cooler water. Therefore the temperature drop between summer and fall months, in terms of its significance on their metabolic rate, really doesn't seem as significant as we like to make it out to be.
At least that's my thinking anyway. |
|
| |
|
Posts: 1291
Location: Hayward, Wisconsin | tcbetka wrote: "Don't forget that we anglers tend to think of warm water temperatures in the summer because the surface temperatures exceed 70 degrees. But in all reality the fish are going to seek out water temperatures most desirable to them...which means finding deeper/cooler water. Therefore the temperature drop between summer and fall months, in terms of its significance on their metabolic rate, really doesn't seem as significant as we like to make it out to be."
LR: Tom, based on my observations while radio tracking muskies in Ontario's Eagle Lake, I particularly disagree with ..."finding deeper/cooler water.", when it comes to digestion. On the contrary, the big muskies (mostly females, but not all) did their feeding in the deeper, cooler (by an average of around 10 degrees F) and then on the average of every third day in mid summer (July) moved as much a several miles to the warmest water available in a fairly shallow bay! My hypothesis, based on these observations was that they were in the warmer water to warm up and speed up digestion. Obviously I couldn't "ask" them when we did recapture them, so I guess we'll never know for sure, but it did make sense to me and Dr. Lebeau and many other seasoned muskie anglers that I have discussed it with. |
|
| |
|
Posts: 152
| Hi Larry, off topic but does any of your data show reduced travel in late fall and into ice times? |
|
| |
|
Posts: 135
| But in all reality the fish are going to seek out water temperatures most desirable to them...which means finding deeper/cooler water.
Yes, and no. Muskies do clearly seek preferred water temps, it's just not deeper/cooler.
The 2011 Melton Hill study using radio telemetry and internal temperature sensors showed that muskies prefer 68-77 degree water when oxygen and forage is available in both cooler and warmer water than that. If only cooler water is available, they congregate in the warmest possible water.
https://www.coopunits.org/Tennessee/Research/Completed/3.8626377729E...
To me, this suggests that if they're moving to an area of cooler water when the preferred warmer water is available, it's because the warmer water doesn't offer something they need (food, oxygen, ???). For example, if they're hungry and the available forage prefers cool water the need to eat will drive them until they're satisfied - but they're not going to stay/live there.
The phenomenon of muskies moving out to deep/cool areas to feed and then up to shallow/warm areas when not feeding is well-observed. Anyone who's cursed the sunbathers on a Minnesota reef or sand flat knows this. But is the shallow move to speed digestion, or just because it feels good to them? Or more likely it does both...increased metabolism and feels nice? I just know that the shallow-structure fish near deep-water forage behave differently than shallow-water fish near shallow-water forage, and this has meaning when trying to catch them.
My personal non-biologist hypothesis is just common sense: they're fat in the fall because they're eating more. Why are they eating more? Because they can...it's easier to feed because the forage is more concentrated in vulnerable near-shore areas. Summer fish with the same easy food access get stupid fat too.
Edited by Glaucus_ 12/11/2017 9:06 AM
|
|
| |
|
Location: Green Bay, WI | I would agree about them eating more forage because that forage is more available. I think they've learned this over many many years of experience, essentially now to the point it has become "instinct" to them. Shouldn't be surprising I guess. My point about them finding cooler water was meant as a further illustration as to how little change in temperature their two extremes might actually be. Since water freezes at 32F and is slightly warmer at the bottom of the water column, then it's not going to be any colder than that. And if they prefer water temperatures around 70F, then the most we're talking about is a 38F temperature range--which may not be all that much when it comes to the activity of their digestive enzymes.
So in terms of why they put on weight in the fall, I still hypothesize that it's because they're 1) eating more forage because it's more readily available, 2) they don't have to do as much work to go get that forage given point #1, and 3) their metabolism has slowed a bit in the cooler water. Whether or not their metabolic rate has slowed significantly might be debatable given what's been discussed thus far (ie; digestive enzyme activity), so maybe it's as simple as them eating more without having to spend as many calories to go get it.
Maybe it really is like us sitting on the couch watching TV, and pigging-out on junk food? |
|
| |
|
Location: Green Bay, WI | Larry Ramsell - 12/11/2017 7:38 AM
LR: Tom, based on my observations while radio tracking muskies in Ontario's Eagle Lake, I particularly disagree with ..."finding deeper/cooler water.", when it comes to digestion. On the contrary, the big muskies (mostly females, but not all) did their feeding in the deeper, cooler (by an average of around 10 degrees F) and then on the average of every third day in mid summer (July) moved as much a several miles to the warmest water available in a fairly shallow bay! My hypothesis, based on these observations was that they were in the warmer water to warm up and speed up digestion. Obviously I couldn't "ask" them when we did recapture them, so I guess we'll never know for sure, but it did make sense to me and Dr. Lebeau and many other seasoned muskie anglers that I have discussed it with.
Yes, I recall those points in the article you wrote. Do you happen to remember the water temperatures that you found in those different places? I'll have to pull out the article(s) and review them this week, because it's been some time since I read through them.
I'll bet their migration into warmer water was instinctive, given the point you made about digestion. I doubt they put much thought into it, LOL. |
|
| |
|
Location: Green Bay, WI | Sudszee - 12/11/2017 8:19 AM
Hi Larry, off topic but does any of your data show reduced travel in late fall and into ice times?
On a related topic to the study that Larry did on Eagle Lake, there is on-going research in the bay of Green Bay right now, on the migration patterns of (angled) radio-tagged muskies. I haven't heard any sort of preliminary results just yet as it just started this year to my knowledge. But there are apparently several listening stations throughout the bay (including up north) that will record any migratory movement from the fish that have been radio-tagged. I don't have a map of the receiver sites, but to my knowledge they are located by the main rivers going into the bay, as well as across the bay up near the Marinette area. Since the data is gathered from these sites periodically, it should give a temporal migration pattern. Then we'll have some idea of the answer to your question...at least for the fish sampled (tagged) in the bay of Green Bay. |
|
| |
|
Posts: 8782
| Makes me think the fish we catch in shallow water have been hanging out there for a few days and are about to head back out into deeper water to feed again. The question then is do they feed in deeper cooler water because they prefer that, or do they just instinctively know that's where the food is?
|
|
| |
|
Posts: 135
| In the Melton Hill study, when forage was available in areas of preferred water temp (68-77) the muskies stayed put. When the food isn't there? Well, species that can't find food get extinct pretty fast.
And being hungry isn't the only reason a muskie hits a lure. It might have just moved in after feeding and it "eats" again because of reaction or claiming territory or just plain meanness and then it's stuck on a hook.
Edited by Glaucus_ 12/11/2017 1:25 PM
|
|
| |
|
Posts: 1291
Location: Hayward, Wisconsin | Glaucus: My tracking work ended in mid September, so I can't personally answer your question. Some tracking studies I have read had the big females moving shallow...UNDER THE ICE (as shallow as 3 feet of water) in or near the spawning grounds.
Tom: Without digging my data out, I believe the deep feeding areas in the main lake basin were around 62 degrees or so and the shallow about 10 degrees warmer. |
|
| |
|
Location: Grand Rapids, MI | tcbetka - 12/11/2017 10:40 AM
So in terms of why they put on weight in the fall, I still hypothesize that it's because they're 1) eating more forage because it's more readily available, 2) they don't have to do as much work to go get that forage given point #1, and 3) their metabolism has slowed a bit in the cooler water. Whether or not their metabolic rate has slowed significantly might be debatable given what's been discussed thus far (ie; digestive enzyme activity), so maybe it's as simple as them eating more without having to spend as many calories to go get it.
You forgot the most important reason. Eggs!! What they eat comes and goes, 6+ pounds of eggs stays put. |
|
| |
|
Posts: 135
| You forgot the most important reason. Eggs!! What they eat comes and goes, 6+ pounds of eggs stays put.
Look at all of the egg mass present in this 38" muskie from October that died during Sean Landsman's study...now imagine what it's like for a mature 50" fish that's much more productive.
Those eggs are carried up pretty high inside the body, so maybe aren't themselves what makes a fish look fat? But they sure push everything else down and out, so anything they eat is bulging.
http://projectnoblebeast.blogspot.com/2009/10/necropsy-notes-genera...
Attachments
----------------
 eggs.jpg (137KB - 629 downloads)
|
|
| |
|
Posts: 8782
| That would explain the additional mass on a female.
Maybe part of it is the caloric content of their diet. Half the food chain comes with a side of eggs in the fall, so basically everything that eats is getting more calories out of a meal. |
|
| |
|
Location: Green Bay, WI | Will Schultz - 12/12/2017 9:36 AM
tcbetka - 12/11/2017 10:40 AM
So in terms of why they put on weight in the fall, I still hypothesize that it's because they're 1) eating more forage because it's more readily available, 2) they don't have to do as much work to go get that forage given point #1, and 3) their metabolism has slowed a bit in the cooler water. Whether or not their metabolic rate has slowed significantly might be debatable given what's been discussed thus far (ie; digestive enzyme activity), so maybe it's as simple as them eating more without having to spend as many calories to go get it.
You forgot the most important reason. Eggs!! What they eat comes and goes, 6+ pounds of eggs stays put.
Well certainly they develop gametes over the winter...but I'm talking about in fall, when the food bag is on. Also, those eggs have to be made from something--I mean, it takes calories to create gametes. Either they convert caloric intake to fat or gametes, but they need more calories either way. How much egg mass can an anorexic musky create after all? |
|
| |
|
Location: Green Bay, WI | Glaucus_ - 12/12/2017 10:57 AM
Look at all of the egg mass present in this 38" muskie from October that died during Sean Landsman's study...now imagine what it's like for a mature 50" fish that's much more productive.
Those eggs are carried up pretty high inside the body, so maybe aren't themselves what makes a fish look fat? But they sure push everything else down and out, so anything they eat is bulging.
http://projectnoblebeast.blogspot.com/2009/10/necropsy-notes-genera...
Very interesting image.
I believe I've read a paper (LeBeau's thesis maybe?) that discussed how the eggs change over the course of the months leading up to the spawn. I believe I remember that the eggs become larger as they ripen, but I read through most of that thesis about 8-9 years ago...if that's where it even was I read this. I believe that it was yolk enlargement responsible for the increase in egg size (mass) as they ripened leading up to the spawn.
Larry, do you remember seeing this information in Dr. LeBeau's doctoral work? |
|
| |
|
Posts: 135
| It all-but goes without saying that the eggs will change and grow between initial development and the spawn. The point is simply that they are present in large numbers already in October, and this undoubtedly is one part of the "fat (female) fish" equation.
In the blog link above, Landsman explains in more detail about the fish shown:
"...took a small portion of the ovaries and counted the number of eggs then extrapolated the total number of eggs using the length of the ovary. There were 606 eggs in a 29 mm/1.1 in segment of one of the ovaries. The total length of the removed ovary was 43.5 cm/17.1 in. I will forego reporting all the calculations, but there were an estimated 18,180 eggs (give or take) in this 38 in female. Scott and Crossman (1983) reported a range of 6,000 to 265,000 eggs in adult muskellunge."
So, a relatively young 38" female had a 17" ovary containing ~18,000 eggs.
Now imagine a mature 50" female with ~200,000 eggs...
|
|
| |
|
Location: Grand Rapids, MI | tcbetka - 12/12/2017 1:10 PM
Will Schultz - 12/12/2017 9:36 AM
tcbetka - 12/11/2017 10:40 AM
So in terms of why they put on weight in the fall, I still hypothesize that it's because they're 1) eating more forage because it's more readily available, 2) they don't have to do as much work to go get that forage given point #1, and 3) their metabolism has slowed a bit in the cooler water. Whether or not their metabolic rate has slowed significantly might be debatable given what's been discussed thus far (ie; digestive enzyme activity), so maybe it's as simple as them eating more without having to spend as many calories to go get it.
You forgot the most important reason. Eggs!! What they eat comes and goes, 6+ pounds of eggs stays put.
Well certainly they develop gametes over the winter...but I'm talking about in fall, when the food bag is on. Also, those eggs have to be made from something--I mean, it takes calories to create gametes. Either they convert caloric intake to fat or gametes, but they need more calories either way. How much egg mass can an anorexic musky create after all?
Eggs start developing in mid/late-August in most areas, by September they're significant and by October 10+% of weight could be eggs. If I recall correctly our modern day record (mid-October fish) had 8# of eggs, that is 14%. So, I'm back to saying that most of any actual "fat" in a fish is accumulated in August and early-September because after that egg growth has to be using up most of the caloric intake. |
|
| |
|
Posts: 8782
| Do you think they're effectively "programmed" to consume more food during egg development? Certainly would explain why the best fishing starts in late august on some of our favorite waters. |
|
| |
|
Posts: 1291
Location: Hayward, Wisconsin | Tom: I believe you are correct about Dr. Lebeau's thesis containing the information you espoused.
Glaucus: 200,000 eggs is miniscule compared to the O'Brien muskie from the Moon River in 1988. According to Dr. Ed Crossman, Dr. Lebeau did an egg count of the ovaries from that fish and found around 850,000 eggs!! Talk about egg bloat.
Also note that yes, eggs do grow until ripe, different waterbodies and different strains of muskies produce different SIZED eggs! This was noted by both noted WDNR Researcher Leon Johnson and WDNR's Art Oehmcke, who was in charge of the Woodruff hatchery during the mid 1900's.
Will: While I agree that 10% of body weight could be eggs in the fall, according to Dr. Lebeau, it could be as much as 20% by the time they are ready to spawn! As for the Modern Day record, it only contained 2 1/3 pounds of eggs (I personally weighed them). It is likely that that fish was at the end of its life or had ceased viable spawning. Also, it contained very little body fat.
EA: good question, but flies in the face of the belief that they eat more in the summer than in the fall due to metabolism. Something we may never know for sure. |
|
| |
|
Location: Grand Rapids, MI | Larry Ramsell - 12/13/2017 7:00 AM
Will: While I agree that 10% of body weight could be eggs in the fall, according to Dr. Lebeau, it could be as much as 20% by the time they are ready to spawn! As for the Modern Day record, it only contained 2 1/3 pounds of eggs (I personally weighed them). It is likely that that fish was at the end of its life or had ceased viable spawning. Also, it contained very little body fat.
Thanks, LR!! |
|
| |
|
Posts: 612
| In September - October - early November on Chautauqua Lake they follow the perch schools. If the perch are at 50' or 12' that's pretty much where the musky are on the outskirts of these schools. I haven't caught nearly as many as some here, but my experiences show they do bite better in the fall. I know when we used to keep big pike a long time back, fish taken in late_Oct-Nov were definitely filling up with eggs, so I suspect the same is true of musky's. |
|
| |
|
Posts: 17
Location: Tampa, Florida | NPike - 12/13/2017 6:27 PM
In September - October - early November on Chautauqua Lake they follow the perch schools. If the perch are at 50' or 12' that's pretty much where the musky are on the outskirts of these schools. I haven't caught nearly as many as some here, but my experiences show they do bite better in the fall. I know when we used to keep big pike a long time back, fish taken in late_Oct-Nov were definitely filling up with eggs, so I suspect the same is true of musky's.
Hmm, interesting.  |
|
| |
|
Posts: 613
Location: Michigan | NPike - 12/13/2017 7:27 PM
I haven't caught nearly as many as some here, but my experiences show they do bite better in the fall.
Are they biting better/more often or are they just all congregated in the same general area which makes them more susceptible to being caught by anglers who know they are there? |
|
| |
|
Posts: 612
| I don't believe they necessarily congregate any more in late fall than at other times of year. In the lakes I "normally" fish, I can generally "using the term loosely" find spots regardless of time of year. |
|
| |
|
Posts: 239
Location: Elroy, Wisconsin | Acids that break down proteins react at rate that is temperature dependent. The higher the ambient temperature the faster acids change sugars, carbohydrates and proteins into simpler compounds. Therefore, Muskies can and do digest proteins faster in warmer water (given adequate Oxygen levels) and they are found there in response to simple biochemical reactions. Then again, maybe they just feel better in warmer water and are happy there after feeding.
Mudpuppy |
|
| |
|
Posts: 8782
| jasonvkop - 12/15/2017 11:24 AM
NPike - 12/13/2017 7:27 PM
I haven't caught nearly as many as some here, but my experiences show they do bite better in the fall.
Are they biting better/more often or are they just all congregated in the same general area which makes them more susceptible to being caught by anglers who know they are there?
Maybe there are just a lot fewer anglers in the fall, and the few that are out there catch all the fish... |
|
| |
|
Location: Green Bay, WI | Mudpuppy - 12/17/2017 7:59 PM
Acids that break down proteins react at rate that is temperature dependent. The higher the ambient temperature the faster acids change sugars, carbohydrates and proteins into simpler compounds. Therefore, Muskies can and do digest proteins faster in warmer water (given adequate Oxygen levels) and they are found there in response to simple biochemical reactions. Then again, maybe they just feel better in warmer water and are happy there after feeding.
Mudpuppy
Exactly, but you're talking about a qualitative assessment, and I was attempting to hypothesize a quantitative one. I'm confident that their GI (digestive) rate is slowed somewhat in the colder water--but by how much? If the water temperature they prefer is 68-70F, and water freezes at 32F, then it can't have dropped more than about 36-38F...right? And this is even less when you consider that we normally fish waters that are no colder than about 38-40F here in Green Bay in the fall. So this means about a 30F temperature drop, compared to their "preferred" water temperatures. Therefore, is the enzymatic activity in their gut halved? I seriously doubt it. Rather I think it's probably down 30-40% at most, which certainly doesn't seem to hurt their GI abilities.
Again, I've caught a number of fall muskies on Green Bay, and invariably they seem to crap all over the boat. So that means their GI tracts have made waste products, and by us handling them...they poop. All over the place. By definition, this could not happen if they hadn't digested their food. So they are certainly doing just that, I guarantee it. Which tells me that their GI activity is still going quite strong in the cooler waters of fall. |
|
| |
|
Posts: 135
| If the rate of digestion (breakdown of food items into usable compounds) slows down in cold water...does the rate of pass-through change as well? Or does peristalsis keep moving things along at the same pace and the food just doesn't get time to be as fully digested before it's kicked out? Someone mentioned earlier that there's a difference between summer poop and fall poop, and that's my experience too: summer seems to be more of a smooth paste, whereas the fall is more clumpy with more easily identifiable items such as scales.
Is it possible that a muskie is getting less food value in the fall due to less efficient digestion? This would lend support to a hypothesis/observation that they eat more, because they'd have to be ingesting more in order to get the same amount of energy if more is lost as waste, let alone to provide the additional energy needed to grow eggs.
I'm not a fish biologist, nor do I play one on TV. But I did stay at a Holiday Inn Express last night. 
|
|
| |
|
Location: Green Bay, WI | Those are great thoughts actually. Especially the GI pass-through idea. I'll have to talk myself through it a bit...
Peristalsis shouldn't necessarily be slowed, but it may be. I mean, it's (largely) driven by the nervous system, which seems to work just fine in these fish even in cold water. Muskies have no problems whatsoever going after a 4-5 mph lure in 40F water, so certainly their motor neurons are firing just fine. I've seen that for myself, and you can also find ample video evidence of it on YouTube. So I'm going to go out on a limb and say that it's unlikely that muskies have a slowed digestive tract in cold temperatures solely due to decreased nervous stimuli of the gut.
With regards to the lumpy vs smooth feces thing, I can't say that I've seen all that much musky poop in the summer--so I can't say I've seen such a difference. That's not to say it doesn't exist...I've just never seen it. And maybe that's saying something right there, in that (as others have mentioned) they simply might have such a high GI transit time, that their gut is empty much of the time? However assuming that their fecal matter IS lumpy in the summer, I would suggest that it might be due to less well-digested portions of their prey. Maybe their GI system is working so fast in the summer that they're actually wasting calories through incomplete digestion? That's an interesting thought, but it might help explain why these fish gain more weight in the fall? So then,
1) Due to a slowed digestive process in the fall (through whatever mechanism), the digestive enzymes have a longer period of time to work on the prey eaten by the fish, resulting in more calories being absorbed...and thus more calories being made available to be converted into musky biomass.
2) Due to a (relatively) more rapid digestive process in the warmer/summer months, the digestive enzymes simply don't have as much time to work on the ingested prey, and thus digestion isn't as complete. Thus there are undigested "lumps" of prey remaining in the fecal matter of the musky.
Is this the case? I honestly don't know. And I don't know how you would ever really prove it, unless you had a musky in a large tank or a pond someplace (fish farm maybe?) and could study this sort of thing over a fairly long time (months to years). But it might well help explain some things in regards to the kinds of anecdotal observations we've been discussing in this thread.
TB |
|
| |
