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SmallstreamOctober 9th, 2007, 3:39 pm
State College, PA

Posts: 103
On one of the recent threads it was mentioned that a fish becomes harder to catch once it is hooked and released. I was wondering if anybody had any knowledge as to if a fish really does figure out what a hook is and do they not feed as much once hooked or do they just become more wary of their surroundings or spooky. If this is the case and fish really do learn this, than that means that they do have a memory and are a lot smarter than I give them credit for. Do the fish remember this traumatic event, say, the next day? Sorry for the odd post but I was just curious.
LamOctober 9th, 2007, 3:46 pm
Lancaster, PA

Posts: 81
speaking as a fish, I must say that I haven't forgotten a thing. Especially when you got frustrated last week and put a worm on your hook to try to fool me. For shame sir, for shame.
MartinlfOctober 9th, 2007, 4:14 pm
Moderator
Palmyra PA

Posts: 3165
A very good question for Jason, if he's around.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
RleePOctober 9th, 2007, 4:28 pm
NW PA - Pennsylvania's Glacial Pothole Wonderland

Posts: 398
>>On one of the recent threads it was mentioned that a fish becomes harder to catch once it is hooked and released. I was wondering if anybody had any knowledge as to if a fish really does figure out what a hook is and do they not feed as much once hooked or do they just become more wary of their surroundings or spooky. If this is the case and fish really do learn this, than that means that they do have a memory and are a lot smarter than I give them credit for. Do the fish remember this traumatic event, say, the next day? Sorry for the odd post but I was just curious.>>

Good thread topic.. I'm not sure what to think a fish actually knows or remembers. One thing I've noticed on streams that get quite a bit of pressure is that there is a clear difference in how fish in 2 different settings react. Fish who lay in the open or usual holding lies will often develop a very jaundiced eye towards any offering that floats past them. They'll bump a fly with their nose or swirl it and not take. But find a fish in a lie that is measurably more difficult to fish and this fish will not be anywhere near as discerning. I've demonstrated this to myself dozens of time, using the same fly and same tippet, etc. on fish in both types of settings. To that end, I tend to think that fish do not so much remember a given fly, etc. as they become increasingly wary of being approached and presented to over and over and over from a certain direction or in a certain manner. I even think that in some cases, heavily pressured fish will choose lies out of the main forage flow because they somehow learn that they need to avoid the places where they also get stuck the most often. Difficult for me to adequately explain. However, I've seen this happen pretty often. Once on the DH area on Muncy Creek, nearly every fish in a 100 yard section was under a big maple limb that was hanging in the water and defying conventional casts. There was all kinds of good holding water all around them, but this is where they all were. And they'd been in the stream for a couple months. They weren't last week's herded-up stockers. I have to believe theat there is something in this behavior that is about minimizing the number of times they are harrassed..
Jmd123October 9th, 2007, 8:22 pm
Oscoda, MI

Posts: 2536
Hey folks, I did a post somewhere else on the site about my fly fishing experiences in Missouri some time ago. I fished at Roaring River State Park down there, which is one of their four "trout parks" - essentially, hatcheries built around massive springs (and they have LOTS of very large springs down there - hundreds of millions of gallons per day, no bullshit). As I described previously, fresh hatchery trout are released every day and are casted to by throngs of waiting fisherman. Many are caught almost instantly by the, how shall I say, "power-bait" crowd, but plenty hold over in the 57 F water below the hatchery. Having watched these fish sipping #16 sulphurs off the surface, plus some similarly-sized cream-colored caddis, I went back the next time with nicely tied imitations, with expectations of successfully matching the hatch. Well, the fish had other ideas - they took a good look at my flies, sometimes follwing them for a foot or two, but rejected EVERY ONE of them.

Were these fish "educated"? YOU BETCHA! They must get just about everything known to man in the way of a fishing lure or fly thrown at them. But these fish weren't getting caught and released, at least I doubt very often - most people who frequented the place were there for the meat (and that's why they were pumping them out by the thousands every day). So, how did the fish get so educated? Perhaps, as in someone's favorite Yogi Bera quote, they learn by observing...

As a follow-up, I fished some other Missouri waters with considerably more success. On a stream called Capps Creek in southwestern MO, I met a man who expressed surprise that he hadn't seen a single trout along the entire stretch of the stream. After which, he mentioned that he had been to Roaring River where all the fish were easily seen...I almost had to chuckle and tell him how REAL trout behave in REAL trout streams, but I kept it to myself. As far as the fishing went, I caught a couple of nice rainbows and a 12" brown (right in front of a couple of old codgers soaking bait from the bank) that made a fine shore lunch. Oh, and all on dry flies - I think an Adams, size 12 if I remember correctly (an old favorite). I should mention that this was also in the middle of the day, with nice warm sunshine - not exactly when I would expect a brown to pounce on a dry fly, though it does happen.

So, here we have a case of obviously visible fish refusing perfectly good imitations of what they're actually eating at the time, while fish that are unseen attack a dry fly that doesn't specifically imitate ANYTHING (OK, I know some might debate that...). Maybe fish that prefer to hang out in the open are extra wary due to their vulnerability, whereas those under cover feel perfectly safe to attack whatever comes their way...???

Some thought to fall asleep by...

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
GeneOctober 9th, 2007, 10:19 pm
Posts: 107Gentlemen:

Do fish remember? As an aquatic scientist I can tell yes they do! Furthermore, there have been a number of controlled experiments that prove this. Here's one of them:

Trout were placed in tanks and and there was trigger of one color that they hit they would get a food pellet. The other trigger (another color) gave them a shock or nothing at all depending on the experiment. The trout learned rather quickly which trigger to hit to get a pellet. The fish were removed from the experiment and placed in other tanks for about 6 months.

When the fish were place back into the original tanks with the triggers. Guess what? The fish remembered which trigger to hit to get the pellet!

Trout survived on this planet for all of these years by being selective and "learning" believe it or not. Not all trout learn at the same levels....just like people. But the natural selection process of evolution allow trout to perceive color, size and behavior as well as what is predator or prey very quickly in the wild or they don't make it. In most instances wild trout are more selective but trout that are fished over constantly "get educated" very quickly.

Trout in spring creeks get a very good look at flies both natural and tied due to the clarity of the water whether those spring creeks are in Missouri or Pennsylvania.

What the angler saw in Missouri is what we refer to as a Compound-complex rise form (coined by Vince Marinaro years ago on the Letort).

Trout must remember fairly well because that's why they feed on one item for so long and that is the basis of fly fishing. If they can eat it and it doesn't hurt them they continue feed upon it. That's why trout are so surprised when they get hooked!

Furthermore, trout are a relatively short lived species. Those that survive and become selective tend to pass their genes down to the next generation and thus the emphasis on wild fish versus hatchery trout where trout are raised for quick growth rather than the characteristics that allow trout to survive in the wild.

Even bass especially smallmouths get selective to lure color, size etc. Ask any bass angler why they have so many lures.

The trout have small brain and large optic lobes so they are sight feeders and this would not have developed evolutionarily if these fish weren't learning and selective because it would make no sense biolgically.

tight lines and selective trout and dumb nymphs

gene
www.eugenemacri.com
Luc384October 10th, 2007, 3:51 am
Belgium / zoersel

Posts: 14
Waw Gene,
Nice testresults! Now we know for sure.
I had a experiance in France where there were a lot of fishermen on the same spot. Trout is hard to cach there and we were trying hard when my son tyed a very strange fly (he made himselve) onto his leader... result... he caught the trout we were fighting for!!! All other welknown patterns were refused by the fish..
Kind regards from
Luc
The worst day fishing is still better than the best day at work!!
www.flyfishingpassion.net
SmallstreamOctober 10th, 2007, 11:38 am
State College, PA

Posts: 103
Wow, awesome replies guys, thanks. What you guys say does make a lot of sense, and what gene says about that research probably tells the story.
TroutnutOctober 12th, 2007, 12:03 am
Administrator
Bellevue, WA

Posts: 2723
Everybody talks about the fact that trout, like most other animals, learn from unpleasant experiences and try not to repeat them. The experiment Gene described shows that. But we have to question whether (and, if so, how quickly) trout catch on to the fact that whatever they ate before getting pulled around the river had a hook in it. When you're used to eating thousands of bugs with all kinds of limbs dangling out in all directions, tumbling at you quickly at odd angles and without giving you a good look, are you really going to notice that one of those legs is in the wrong spot and made of metal?

I don't think so. I do believe trout become harder to catch the more often they're caught, but I don't think it's because they learn to recognize a hook, a dragging drift, or a poor imitation as a sign of danger. There's a simpler explanation, and it has to do with why trout really become selective.

Selectivity

I suspect that selectivity in trout evolved long before the first artificial fly was ever cast, and that its original and main purpose is to minimize ingestion of debris. Trout are on a tight energy budget: they have to take in more energy than they expend swimming and digesting and spawning. If a trout eats a piece of debris (say, mistaking a twig for a caddis larva), that means it wasted energy swimming over to capture the twig, it wastes energy trying to digest the twig, and precious space in its stomach is occupied by a useless twig.

When trout are feeding opportunistically, they do eat lots of useless debris. They can't help it. You have to snorkel (or at least stick your head under) in a stream sometime to appreciate what a tough job it is to be a drift feeding fish. From a trout's-eye view, everything in the drift comes at you fast, at weird angles, in weird lighting, and you've got to make near-instant decisions about whether to eat something or not. Your targets, aquatic insects, come in thousands of shapes and sizes and most of them are camouflaged to look like the debris you want to avoid. Mistakes are a regular and inevitable part of a trout's diet.

It's very tough to make that "food" or "not food" determination. Selectivity allows trout to make an easier choice. "Size 16 female Hendrickson" vs "everything else." Or any other specific bug vs "everything else." There's a lot of debris that looks like it might be food, but not much that looks like a size 16 female Hendrickson. The chance of a mistake is much, much lower.

Of course, this comes at a cost. A selective trout misses out on all the other types of food that drift by. It only makes sense to do that if the trout can pretty much eat its fill anyway. That explains why trout usually don't become selective unless they're feeding on something that's really abundant.

I think most of the time when trout are selective and tough to catch, they're actually employing this ancient debris-avoidance mechanism rather than being hook-shy. But how does this explain why they become harder to catch the more often they're caught?

"Hook-shyness"

I think trout are often aware when they eat something bad. Maybe they spit it out, in which case they only wasted the energy spent capturing it, or maybe it doesn't crunch up and feel right as it goes down. They know that when they feed selectively, they don't have these bad experiences.

So trout face a trade-off. When they're selective, they pay the cost of missing out on some good food. When they're opportunistic, they pay the cost of eating things they shouldn't. Their feeding behavior is a constant balancing act between these two opposing costs.

When one of those costs changes, so does the balance between them. When a feeding mistake leads to the near-death experience of being caught, suddenly the average cost of a feeding mistake is MUCH higher. This means the trout should be more prone to feeding selectively and avoiding mistakes.

Summary

I think I've given the most natural explanation for why trout are so picky. There is no advanced learning or recognition of hooks or drag or anything else involved. Being caught just moves the slider on a natural spectrum of caution which has nothing to do with humans.

I think we give ourselves, and the trout, too much credit for the difficulty of the game we play. But that doesn't diminish the reward of winning.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Jmd123October 12th, 2007, 8:57 am
Oscoda, MI

Posts: 2536
Good points, Jason! I think you may be right with the selectivity argument. What it means for us fly fishers is we HAVE to get it right in order for the trout (or other species) to want to eat it, and that "educated" fish simply are very good at rejecting those objects that don't completely, or almost completely, look like the food item that they're keyed in on. My sulphurs and caddis that were rejected in MO were typical impressionistic dry flies, the sulphurs tied in classic dry fly style and the caddis were elkhairs (almost always use these when fishing caddis hatches. The water at this location is coming straight out of the ground and is crystal-clear - giving the fish a very good view of what's floating along above them. Like I said, these fish sometimes followed beneath my fly for a foot or two to get a really good look - and their impressionistic nature didn't look enough like the actual bugs for them to be acceptable.

The bluegill and smallmouth on the Huron where I live don't seem to be too selective during mayfly and caddisfly hatches, but they became so during flying ant falls - I didn't have anything that properly matched in these cases (i.e., nothing small enough!) and I didn't get many hits.

Heading for salmon waters this afternoon! I will be taking my tying goodies to create some big streamer flies and egg patterns to throw at them with my 9-weight...

Jonathon
No matter how big the one you just caught is, there's always a bigger one out there somewhere...
GeneOctober 12th, 2007, 11:08 am
Posts: 107Jason:

Unfortunately your argument sounds logical to fly anglers one would think that it has to be true and many would believe, but alas there are many flies in the ointment.

1. first of all trout do not feed the same way. Some trout feed inefficiently especially hatchery trout and even some wild trout. Years ago the legendary fishery biologist Robert Butler explained this very well in a presentation before Fly Fishers of Harrisburg. In his presentation he stated that trout are just like people. Some are smart, some are dumb, some are gluttons etc.

2. Most trout feed opportunistically at some time. These are obviously the easiest trout to catch but I don't believe however, we are not really talking about these fish but are talking about how trout become selective. I believe you are missing the idea that trout selectivity in itself is simply a result of feeding mechanism, availability etc. Selectivity is the result of myriad of inputs that we don't have the time to go through on this forum however, consider this: the majority of selectivity of trout is result of the food supply, the turbidity, and the fishing pressure.

In a headwater streams brook trout are very opportunistic and will grab at most things that float by naturally enough. This is a survival mechanism because these stream are relatively barren as compared to others. Brook trout in Big Spring Creek in the Cumberland Valley of Pa are seldom opportunistic feeders even when they are small because the stream's food base is off the charts. Furthermore, there are extremely large populations of just a few organisms (which contrary to what many fly anglers believe is typical of these types of streams) such as sulfurs, blue winged olives, scuds, cressbugs etc. Many of the mayflies have a large emergence period which give the trout a good impression of the pattern over time thus more selectivity. Add the water which is clearer than gin and the subtle currents and you have environment for selectivity. It's the environment that creates the selectivity in trout in many instances but not all. Notice we haven't even mentioned fishing pressure yet and what role that plays in the mess.

3) The idea that the insect must be abundant for the fish to be selective and therefore an efficient feeder etc seems so scientifically accurate.....but it's not. You have run into what we call a circular argument. Here's one of the best examples of why this is just completely wrong sometimes (but not all the time). In Loch Ness in Scotland when they were searching for Nessie the biologists decided to do fish and invertebrate studies also to see if the fish population etc. could support a so called Nessie. What they found was this: that there were a lot more trout (char) in the so called dark waters than they thought and the loch was much more productive than previously realized. But what really blew their minds was what the fish ate. In a category of invertebrates a type of midge larvae ranked last on the quantity in the Loch but the was the most abundant in the bellies of the trout ( in fact it was in such a small quantity they just couldn't believe it)! The biologists couldn't understand why the fish would feed so inefficiently (at least that's what they thought) and selectivitely on these tiny invertebrates. But most fly anglers who have fly fished for a very long time would have no trouble understanding that selectivity is the result of not a super efficient mechnaishm in fish that many anglers believe. It can occur at any time for many reasons we don't know. Sometimes trout do feed efficiently by our standards but the only standards that matters is that of the fish. What Loch Ness also showed the biologist was just how well these trout could see in the murky waters of the Loch.

In spring creeks trout typically feed on midges often times not very efficently by our standards. Gary Borger in an interview once told me of a stream (I believe it might have been in Wisconsin..a spring creek) where because of fishing pressure the trout just refused to take large flies and would only feed on midges! Now did they understand that larger flies would get them caught...I don't know but we see the same things on these spring creeks in the Cumberland Valley.

4. Finally Jason your comment on what the fish eat during opportunistic feeding---the debris, twigs, algae etc. Does that stuff kill the fish? No, they usually ingest all types stuff like that when they grub for nymphs or caddis flies or when they feed opportunistically. Do the fish have the instincts to know this stuff won't hurt them AND THAT IT IS MORE EFFICIENT TO TAKE EVERYTHING IN, IN TERMS OF ENERGY CONSERVATION THAN TO SELECTIVELY SPIT IT OUT OR AVOID IT!

Just food for thought!

gene
www.eugenemacri.com

trout fear me and rightly so!

TroutnutOctober 12th, 2007, 12:37 pm
Administrator
Bellevue, WA

Posts: 2723
1. first of all trout do not feed the same way. Some trout feed inefficiently especially hatchery trout and even some wild trout.


I don't see how that's inconsistent with my argument. Of course there's individual variation in feeding behavior, due to genetic variation, current habitat, and individual life history. The latter includes not only origin (hatchery/wild) but also the number of times an individual fish has been caught or has fed on heavy hatches.

2. Most trout feed opportunistically at some time. These are obviously the easiest trout to catch but I don't believe however, we are not really talking about these fish but are talking about how trout become selective. I believe you are missing the idea that trout selectivity in itself is simply a result of feeding mechanism, availability etc. Selectivity is the result of myriad of inputs that we don't have the time to go through on this forum however, consider this: the majority of selectivity of trout is result of the food supply, the turbidity, and the fishing pressure.


I guess I didn't explain my argument well enough, because I'll be the first to admit that all trout are opportunistic some of the time, and most of them are opportunistic most of the time. I believe they all have the capacity to be selective, and that selectivity is triggered by the extreme abundance of near-identical food items.

The idea that the insect must be abundant for the fish to be selective and therefore an efficient feeder etc seems so scientifically accurate.....but it's not. ... In a category of invertebrates a type of midge larvae ranked last on the quantity in the Loch but the was the most abundant in the bellies of the trout ( in fact it was in such a small quantity they just couldn't believe it)!


I would like to read that study, but I don't think it proves me wrong. When I say an insect must be "abundant" to trigger selectivity, I mean that it is abundant enough in the current encounters of a particular trout that the trout can get all the energy it needs by focusing on that one food. Many insects which are not generally abundant in a water body's population are locally abundant in some microhabitat. If that's where the trout's feeding, it could be selective to something uncommon.

Also keep in mind that just because a trout has a stomach full of something, that doesn't mean it was feeding selectively. It might have found a good way to get that particular food, but that doesn't necessarily mean it's rejecting all others. It might just not be seeing much other food. I've caught several trout with stomachs full of one thing, which struck a fly imitating something completely different.

In spring creeks trout typically feed on midges often times not very efficently by our standards. Gary Borger in an interview once told me of a stream (I believe it might have been in Wisconsin..a spring creek) where because of fishing pressure the trout just refused to take large flies and would only feed on midges! Now did they understand that larger flies would get them caught...I don't know but we see the same things on these spring creeks in the Cumberland Valley.


Trout feeding exclusively on midges would be consistent with my ideas above. If they can improve their accuracy by focusing on midges, then rejecting everything else -- whether it's large or not -- can make sense. The reason they reject a big juicy beetle while midging, for example, is that it might also be a big not-so-juicy piece of bark. They aren't thinking that -- it's just the reason driving the mechanism.

4. Finally Jason your comment on what the fish eat during opportunistic feeding---the debris, twigs, algae etc. Does that stuff kill the fish? No, they usually ingest all types stuff like that when they grub for nymphs or caddis flies or when they feed opportunistically.


No, those things don't kill the fish, but they do waste energy. If a trout eats a caddis larva, the fact that the case is along for the ride is not a problem -- the trout still gained a lot of energy from the larva. The problem is with expending energy to catch and digest something which gives no energy back. The more often a trout does that, the less efficient it is, and the less energy it has to grow or survive. Minor inefficiencies add up to long-term competitive disadvantages over more efficient fish.

Do the fish have the instincts to know this stuff won't hurt them AND THAT IT IS MORE EFFICIENT TO TAKE EVERYTHING IN, IN TERMS OF ENERGY CONSERVATION THAN TO SELECTIVELY SPIT IT OUT OR AVOID IT!


No, it's not always more efficient to take everything in -- even with the charitable definition of "everything" as "everything an opportunistic trout would judge to be food." (As opposed to everything that drifts by, which would probably be 95% debris or so.)

There are many situations in which feeding opportunistically is the most efficient method -- when multiple foods are needed to get full. But if a trout can fill up on a single food, then it's more efficient to do just that. The opportunistic trout may end up digesting a stomach full of 70% food 30% debris, while the selective trout digests a stomach of 99% food 1% debris... selective trout wins.


Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
SmallstreamOctober 12th, 2007, 12:49 pm
State College, PA

Posts: 103
I dont know about you guys, but its nice to know that there are other people out there more obsessed with trout fishing than I am. I dont feel so bad, haha. you guys are crazy, but in a good way lol!
GeneOctober 12th, 2007, 2:37 pm
Posts: 107Jason:

Sorry I don't buy your debris theory at all. Trout evolved to take in a certain amount of debris and this I believe is immaterial in the equation. I don't find anything in the literature that suggests otherwise. In fact some scientists aren't sure whether algae, sticks and other plant substances are consumed accidentally or actively eaten! Your so called minor inefficiencies are are expressed by all trout. It's the times they pound up that make up for these so called efficiencies.

Selectivity of trout encompasses a myriad of possibilities including some of the following:

1) Competing species--other trout species
2) other competing fish..such as Chubs. because in some streams the chubs mouth is more efficient at bottom feeding tool than brook trout; the brook trout diet actually changed to zoo plankton in open water stretches (I believe this was done in Quebec).
3) As we both agree the abundance of food supply
4) seasonal variation on the food supply etc.
5) It is well know that trout will take advantage or be opportunistic of certain food items.......if that item is preferred food item to begin with. "But the total density of drift is only loosely associated with feeding activity in trout; peak occurrence of preferred items in the drift may not correspond to the peaks in total drift volume." Sometimes they take in a variety of things in the drift at other times they have a preferred food items even in these situations.

However it should be realized that the trout feeding during this so called opportunistic time often spit out certain insects (trout appear to be able to taste certain things); trout will chew somethings and either swallow or spit them out. Furthermore, according to Willers and other trout tend to get more selective when hungry. When trout selectively rise to a single insect there is usually a rhythm to their feeding cycle (and thus higher efficiency but this does not happen all the time; often true years ago on Falling Spring during trico time). This goes back to the "imprint" the pattern makes on the fish and the fish' selectivity. This imprint allows the fish to keep feeding successfully without getting killed. Over time this imprint on some streams due to the length of emergence, clarity of water etc. gets more refined and thus harder to fool the fish. Notice I haven't talked about fishing for these fish yet! You can easily see this on the Green Drake Hatch on Penns Creek. Most of the trout continue to rise for Sulfurs on most stretches of the stream even though the larger drakes are on the water even though by quantity of flies and the size the flies the drakes dwarf the sulfurs. Why? Do they like the taste (some of us believe so). But the trout are feeding on more of the safe imprint because that refined imprint has allowed them to survive. Why would most of the trout feed on finger food when they could gouge on millions of big drakes floating and hatching ( in terms of efficiency). This often baffles fly anglers. But remember the statement I made above about preferred food items! The sulfurs are a preferred food item and I've seen this everywhere with this species both east and west.

When you throw in fishing pressure that takes the selectivity thing to a whole new zone.

I didn't explain myself clearly with the Borger inteview. He basically said the trout's condition he thought was deteriorating due to the fishing pressure because of the selectivity of the midges against large food. I've also seen this on other streams where trout refuse to eat larger items and the so called "condition factor" of the fish decreases due to stress and overpressure.

Also in the case of the midge larvae in Loch Ness according to the documentary I saw and the interviews ( I believe it might have been BBC production) the trout would have actively sought out these minute larvae and they were in such small quantity that it was astounding. Could they have gained some type of advantage ...don't know. Maybe no one fished midge larva? But in such a large place would that have made any difference?

My points are this:

1) trout do not always feed efficiently ( do humans?)
2) trout feed most efficiently during a hatch when they are probably taking a single preferred food item in rhythm
3) opportunistic trout are sometimes feeding more selectively than we think; don't believe a trout can't ascertain something in a second or two coming by him in a drift because it would make no sense evolutionarily to begin with. That's why the debris thing doesn't make much sense to me.
4) trout will sometimes feed selectively to their disadvantage due to fishing pressure (which makes sense biologically)
5) certain stream environments lend themselves to more selective trout due to food supply, clarity of water, strain of trout, fishing pressure etc.
6 trout actually feed more selectively when they are hungry
7 laboratory studies prove trout have preferences for food types, colors, and specific behaviors related to these items.

8 the first job of a trout is survival. All things relate to survival whether they know it's a hook or not is immaterial. Many of them know t they were caught on and thus the more refined imprint pattern during selective feeding. In most instances of wild fish (not hatchery pets) that have heavy fishing pressure these fish are survivalists and the difficulty catching them involves the simple fact that environmental and fishing pressures makes the fish more selective. This can be advantage or it can be a disadvantage. For example, the most native instinct of a trout is cold water. Trout will sometimes enter springs and other streams in summer months even though these areas may contain high nitrogen or other harmful gases or perturbations which eventually harm them because cold water is the overlying survival mechanism.
9) It's not only the percentage of food in a trout's stomach but what type of food it is! What's the fat content protein etc. Once again the ideal of debris just doesn't make it in anything I've read or seen in the literature. Furthermore, a trout would usually do better on a variety of protein, carbo, fat and fish diet than just one item. The selective hatch phenomenon is part of the overall pattern of feeding of a trout it may for a short time be the most efficient.
10) In stream studies with artificial streams and streams with no fishing pressure often times a different picture will emerge to show the trout's preference for larger invertebrates in any population. But once a great amount of fishing pressure is applied to any system the trout usually become more selective and it is a survival mechanism.
11) in studies on fish it has been shown that stress causes the fish to release certain hormones (cortisol) in some waters. Do other fish in our case trout pick up these up these odors and what response do they predict in the other fish?

12 Finally trout are not super machines which always feed efficiently. They may feed opportunistically and sometimes can do it selectively other times not at all. They can feed selectively due to a variety of circumstances and in some cases this may actually be bad for the trout. There is not one way or one method and when we talk of this we are talking about hopefully the majority of trout in the population but we should all remember this: it may be a game to us; but it's not a game to them. Their instincts are to survive which goes back to the original question someone posed. Yes, trout are selective. They can learn. They perceive color very well. They can also see things quicker in a current than we believe they can. Fishing pressure and environmental conditions may increase this selectivity. And yes, I believe that the main reason for selectivity is survival whether it's efficient feeding or not to get caught since the trout must survive under these changing conditions of fishing pressure. Efficiency alone is not the answer on streams that are fished over and over.

gene
www.eugenemacri.com

somewhere they are rising..I just know it...and so do you!
TroutnutOctober 12th, 2007, 4:13 pm
Administrator
Bellevue, WA

Posts: 2723
However it should be realized that the trout feeding during this so called opportunistic time often spit out certain insects (trout appear to be able to taste certain things); trout will chew somethings and either swallow or spit them out.


That's true -- there's more complexity to opportunistic feeding than "eat everything that comes along." Taste and preference are issues. I just think there's a bigger, better explanation for true selectivity than just an extension of these sorts of preferences.

You can easily see this on the Green Drake Hatch on Penns Creek. Most of the trout continue to rise for Sulfurs on most stretches of the stream even though the larger drakes are on the water even though by quantity of flies and the size the flies the drakes dwarf the sulfurs. Why? Do they like the taste (some of us believe so). But the trout are feeding on more of the safe imprint because that refined imprint has allowed them to survive. Why would most of the trout feed on finger food when they could gouge on millions of big drakes floating and hatching ( in terms of efficiency).


That's a good question, but again I believe my debris hypothesis gives the best answer. Selectivity is a simple, limited instinctual tool that can explain a lot of these perplexing behaviors. Many of them are misfires of this overall beneficial mechanism. When trout are selective (or "fixated," the term Gonzo prefers and a better one to use here) they see only two categories of items in the drift: "target" and "non-target." Cognitive limitations prevent them from juggling multiple types of targets or thinking much about which non-targets are or are not food.

They're basically in a trance that doesn't break until the abundance of the target falls below some situation-specific point. This explains why they ignore green drakes to keep feeding on sulphurs: they're fixated on sulphurs until the sulphurs trickle off, regardless of what else is going on.

If it were, as you suggest, a matter of preferred species, then we would see trout feeding selectively on green drakes eagerly switch to sulphurs before the drakes are done, for the same reason they stick with sulphurs when the drakes start. (Don't read too much into the specific species or emergence order there -- my point is that, if preferred species are the explanation, then trout would frequently stop a selective trance to switch to that species.) Instead we see something more like inertia: trout in a selective trance want to continue that selective trance until they're no longer getting enough food.

This "inertia" is not a pro-efficiency feature of selectivity, but a cognitive limitation. Trout can't fixate on a target food while evaluating other potential target foods at the same time. This leads to some inefficient decisions around overlapping hatches, some negative side effects. But those have been outweighed, over lifetime and evolutionary time scales, by the positive effect selectivity has on efficiency.

Here's my idea in a nutshell: Trout don't think about efficiency. They have just evolved to follow a very simple rule which, in the long term, increases their efficiency. That rule is: Be opportunistic by default. If you find lots of one type of food, then become selective/fixated/entranced until there's not enough of that food. I think this is the simplest possible explanation from which we can logically deduce the perplexing selective behavior we see. (Much of the complexity, including effects of angling pressure, falls into how specific trout define "lots" and "not enough.")

I didn't explain myself clearly with the Borger inteview. He basically said the trout's condition he thought was deteriorating due to the fishing pressure because of the selectivity of the midges against large food. I've also seen this on other streams where trout refuse to eat larger items and the so called "condition factor" of the fish decreases due to stress and overpressure.


That's a really interesting point I hadn't seen before, and it could very well be correct. However, I think it is consistent with my explanation of selectivity and fishing pressure. I said trout are constantly balancing the cost of missed opportunity (bypassing good food) versus the cost of feeding mistakes. The cost of feeding mistakes = the cost of wasting energy eating debris + the cost of getting caught. When there's no angling pressure, selectivity works to maximize feeding efficiency. Adding angling pressure tips the equation in the direction of being more selective than would be energetically optimal otherwise. Enough of this unnatural manipulation would naturally lead the fish to be so selective their condition suffers.

1) trout do not always feed efficiently ( do humans?)


I'm not saying they always feed efficiently. But having a simple mechanism which adds to their efficiency in the long term gives them an evolutionary advantage over fish without that capability.

3) opportunistic trout are sometimes feeding more selectively than we think; don't believe a trout can't ascertain something in a second or two coming by him in a drift because it would make no sense evolutionarily to begin with. That's why the debris thing doesn't make much sense to me.


I'm not saying opportunistic trout are completely unscrutinizing gluttons. They manage to take mostly food from a drift which is overwhelmingly debris. That's impressive. If it's as high as 90% food, it's amazing. But a trout feeding selectively probably gets almost 100% food. That's a 10% advantage over an opportunistic trout. Add that over every hatch all spring long, and maybe the selective trout has an extra half-inch on him when spawning season rolls around and he wins the mate. That's the kind of difference I'm talking about here... subtle advantages which favor this adaptation over the course of many generations.

7 laboratory studies prove trout have preferences for food types, colors, and specific behaviors related to these items.


And all these things may come into play during opportunistic feeding, and even in determining how quickly trout become selective (or stop being selective) to certain foods. But I think selectivity itself is independent of these preferences.

And yes, I believe that the main reason for selectivity is survival whether it's efficient feeding or not to get caught since the trout must survive under these changing conditions of fishing pressure. Efficiency alone is not the answer on streams that are fished over and over.


I agree, but I'm not saying feeding efficiency alone is the answer. Feeding efficiency is the original reason for selectivity. It's the original reason trout evolved a mechanism for extreme accuracy, for which they pay an opportunity cost. It's why they balance that against the cost of feeding mistakes. But the cost of feeding mistakes is paid not just in feeding efficiency when angling pressure is involved. Angling pressure shifts the balance by adding huge energy and survival consequences to feeding mistakes. This dramatically shifts that balance of costs, and the natural result is that fish are more selective.

By the way, this is a great discussion. It's really helped me refine my ideas. My "theory" is still just a set of untested ideas, although I think they're very good ones and probably correct, but I'm open to changing them or giving them up if contradictory evidence prevails. I just haven't seen any evidence or arguments yet which convincingly contradict what I'm saying.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
TroutnutOctober 12th, 2007, 4:21 pm
Administrator
Bellevue, WA

Posts: 2723
I dont know about you guys, but its nice to know that there are other people out there more obsessed with trout fishing than I am. I dont feel so bad, haha. you guys are crazy, but in a good way lol!


Welcome to Troutnut.com!
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
DanoOctober 12th, 2007, 9:29 pm
Vanderbilt, Michigan

Posts: 101
Tim,

Using human behavioral terms such as "figure out", "remember", "learn", etc. and applying those terms to "trout" is a loosing proposition. So the short answer is: They don't think, they react purely to stimuli, they don't "remember" they become conditioned (for lack of a better term). I can't count the number of times I've "missed" a strike only to come back an hour or so later and net the same fish after "pricking" it....

While this is a very interesting discussion, it is somewhat overwhelming even to one who has been fishing for over half a century.

Any meaningful discussion on fish behavior should be species specific and then one would need to look at the behavoir of the one pound Brown at the tail of a pool and how it's behavior differs from the 5 pounder at the head of the pool (Browns being very territorial).

"Selectivity", IMHO, is much overused, or at the least much misused. Example: Angling for Brown trout in gin clear waters, where Eagles, Ospreys, mink, and other predators are abundant, the fishing pressure very low, yet your offering is "refused". Is this "selectivity" or "warriness". In my book it's "warriness"; any hint of a shadow will keep 'em down. Remember Browns are nocturnal, territorial, and primarily bottom feeders....(they also aren't a trout). Thus they "behave" almost completely different than a Raindbow, which will "behave" differently than a Brookie, and so on and so forth....

Bottom line, in my experience, is to know the two basic priorities of any fish; cover and food. To understand the food chain; the bigger the fish the higher up the food chain it is. Fish are basically "lazy"; they will expend the least amount of energy for the greatest amount of food (if a trout "needs" to just lie at the bottom with it's mouth open and let the midge larvae stream in it will do so). Always be stealthy, the lateral line of any fish is it's primary line of defense (or offense). Know your quary; learn how to react like a fish. Presentation is most important, size is second, actual pattern is third.

I can honestly say that in 50 years I've never met a selective trout but have had the distinct pleasure of meeting a hell've alot of wary ones. Mebbe that's because I don't angle for 'em; I hunt 'em...FWIW.

Dano



Eventually, all things merge into one...and a river runs through it.
GeneOctober 12th, 2007, 9:29 pm
Posts: 107Jason:

Is there anyway we can get paid for this continuing discussion; this is more fun than work! However, you are using some great logic in your discussion which makes me think you haven't been fly fishing too many years ( because sometimes too much logic is the bane of fly fishing)? Am I correct on that? How do I know this? If one fishes the sulfurs long enough one knows that the sulfurs do not have to be in great abundance for the trout to ignore the drake. Trout do have a certain preference for certain foods. The sulfurs are on the stream for a long time and thus have a refined imprint to the fish. This might be efficiency but it appears that it is more preferred selectivity which happens all of the time. Trout not only get conditioned to the sulfur but to their behavior the longer the hatch goes on. Even when the sulfurs peter out the few that are left are selectively taken versus the greater quantity of large flies.

I'll give you another example that many fly anglers have probably seen something similar over the years. Certain caddisflies have a slashing types of emergence pattern. I've seen trout so conditioned to this type of emergence on stretches of some streams that when this hatch has basically finished after a few days the fish remain conditioned to feed on this type of fly for days after even though there are tons of other insects on the water. I have proved this over and over again by taking such fish with a certain patterns and motion which imitate this. I have watched trout for days doing this on tons of streams. It's common place. Your entire theory seems to based on efficiency and abundance; this I'm sorry I believe from both biological sense and fishing sense is incorrect. You should search the literature for many examples trout preferred food especially under fishing pressure and certain environmental conditions. Selectivity evolved as a survival mechanism for trout. It allows trout to perhaps to feed efficiently sometimes but is most likely the result of the organism not hurting the fish. Trout can feed selectively without feeding efficiently; they do it all of the time

There are tons of examples in the animal kingdom of what animals eat by similar survival mechanisms. Birds have evolved similar survival selectivity. You should read studies which show interpecfic competition of trout even in set up conditions show that one species of trout will force another species of trout to change it's preferred food in foraging. Is this efficiency or is this a survival mechanism? Here's link to an abstract on one such study: link to allenpress here

You make too much of gut contents in terms of percentages. It's also what the fish ate that gives it energy.

I totally disagree with your target and non targeted theory. I have not found anything over the years in the scientific literature which will support that. Of course if a trout or any other animal feeds efficiently this should give it an advantage however they don't need to feed efficiently to be very selective. Selectivity once again is a survival mechanism... and trout may be a lot smarter than we think!

Your theory on spawning is also of limited usefulness. You are trying to force trout into some basic evolutionary theory you have hatched rather than take what we know about the fish and use it. For example, in salmon and in trout studies show that precocious smaller males sneak in and fertilize the eggs and they are extremely efficient at it. Check the literature. The theory of what is a dominant male or who wins the mate is more fiction often times than scientific fact. Any good deer hunter who has been in the woods for many years will tell you that sometimes the big doe runs off with the buck who actually lost the battle. Some might say that it doesn't make sense but it really does because in an ecological system the more aggressive animals tend to get shot or killed earlier and use too much energy and thus nature has provide a range of variations to make sure the most animals are produced...survival!

And finally I know you are just starting your career in the fishery sciences so read lots and lots of papers and books and I think you eventually come to the conclusion that your theory needs more work.

One final point are you sure we can't make big living doing this? Perhaps we can ask for donations or something.

Take care Jason

and stay away from those Alaskan Girls cause I heard they just want your fishing equipment!


gene

www.eugenemacri.com
TroutnutOctober 12th, 2007, 11:47 pm
Administrator
Bellevue, WA

Posts: 2723
They don't think, they react purely to stimuli, they don't "remember" they become conditioned (for lack of a better term).


That's a very good point almost everybody in our sport overlooks at one time or another.

Besides, it can't do much for our egos to think of our sport as a match of our wits against a fish. It is much more impressive -- and, luckily, more realistic -- to think of it as matching our wits and skill against millions of years of evolution.

Any meaningful discussion on fish behavior should be species specific and then one would need to look at the behavoir of the one pound Brown at the tail of a pool and how it's behavior differs from the 5 pounder at the head of the pool (Browns being very territorial).


I don't really think that's true. We can study common trends while being fully aware that there are plenty of exceptions. This whole selectivity debate, for example, means nothing in the context a 5-pound brown that eats an 11-inch sucker once every three days and very little else. There are other feeding modes altogether, like chasing minnows or trying to knock scuds out of the weeds. But drift feeding (and selective drift feeding) are both very common.

Pretty much all questions in ecology have to be broken down into pieces before we can say anything meaningful. This is a good piece to study.

"Selectivity", IMHO, is much overused, or at the least much misused. Example: Angling for Brown trout in gin clear waters, where Eagles, Ospreys, mink, and other predators are abundant, the fishing pressure very low, yet your offering is "refused". Is this "selectivity" or "warriness". In my book it's "warriness"; any hint of a shadow will keep 'em down.


Selectivity certainly isn't the only thing that can make trout hard to catch. People probably do frequently spook fish and then attribute the failure to selectivity. But I think there are also times -- even with fish that receive no fishing pressure -- when trout key on one species and will ignore everything else, even real insects. And that's the phenomenon I'm talking about.

Lloyd Gonzales (Gonzo on this forum) included in his book a compelling argument against using the word "selective" in favor of "fixated." He says "selective" connotes more of an active, considered decision between two alternatives, whereas "fixated" better fits the trance-like state we really observe. He's right that it's a better word, but I still use "selective" because it's so well-established already.

Remember Browns are nocturnal, territorial, and primarily bottom feeders....(they also aren't a trout).


They do plenty of daytime surface feeding, too. They have a stronger tendency to be nocturnal or to hang near the bottom or under wood than other species do, but they're also the species most commonly found selectively drift feeding.

If brown trout aren't trout, what it a trout? Browns are Atlantic salmon, rainbows and their offshoots (the goldens and cutts) are Pacific salmon, brookies and lakers are char... what does that leave us? Do I have to rename my website in light of the fact that trout, technically, do not exist? I think we can all keep using "trout" for what it is -- a common name applied by tradition, without any rigorous taxonomic meaning.

However, you are using some great logic in your discussion which makes me think you haven't been fly fishing too many years ( because sometimes too much logic is the bane of fly fishing)? Am I correct on that?


I've been doing all kinds of fly fishing this summer, but I'm in grayling territory here, and they're not usually as challenging as selective trout.

How do I know this? If one fishes the sulfurs long enough one knows that the sulfurs do not have to be in great abundance for the trout to ignore the drake.


I thought someone might bring that up. I am a less clear on how that works, but I believe it's due to another "inertial" effect.

A trout is taking a chance every time it acts selective: it's gambling that more of whatever target it's seeking will be coming along soon. If it becomes selective to a "false alarm" of a hatch and then sits there waiting for something that isn't coming, it wastes energy. If it has fed for several days on a reliable hatch like the sulphurs, this risk is lowered, and therefore so is the threshold for becoming selective. This fits with your idea of an imprint... it's just a more detailed way of describing how I think the imprint works.

Of course, I'm not ascribing any of this careful reasoning to the trout. I just think these may be the forces that guide the optimal long-term behavioral rules toward which the trout's instincts evolve.

Another thing I know from fishing sulphurs that the fish don't key on them much during their earliest hatches, but trout really stick with them as the hatch tails off. This is consistent with an inertial effect, but not with a species preference.

Selectivity evolved as a survival mechanism for trout. It allows trout to perhaps to feed efficiently sometimes but is most likely the result of the organism not hurting the fish.


It is very uncommon that a piece of food would hurt a trout unless there's a hook involved, right? So are you suggesting that selectivity evolved as a defense against fishing pressure? I really don't think that makes sense. For one thing, a few hundred years isn't a very long time to evolve such a fine-tuned mechanism. For another, there are hundreds or thousands of separate lineages in all species of trout which date back to before the birth of modern fly fishing. The capacity for selective trances seems to be present in most or even all populations of trout, so it would make sense that it had to evolve before most of these lineages diverged. It evolved then not to save them from woolly mammoths with ivory 5-weights, but to give them a slight edge in efficiency.

Trout can feed selectively without feeding efficiently; they do it all of the time


As I've said, selectivity isn't perfect. It misfires frequently. But all it has to do is offer an improvement in efficiency, on average, over an evolutionary timescale. And I think it does.

Is this efficiency or is this a survival mechanism?


Efficiency is a survival mechanism. The concept of efficiency underlies most of the field of foraging ecology and much of the rest of behavioral ecology. The most efficient forager has the most energy available for growth, reproduction, and predator avoidance.

I totally disagree with your target and non targeted theory. I have not found anything over the years in the scientific literature which will support that.


Nobody has really looked into it in the scientific literature. It's an open question. I think it hasn't been studied much because (a) there don't seem to be any direct management implications, (b) it's so specific to trout in specific situations that it's not likely to lead to general theory applicable in other areas of ecology, and (c) it's hard to collect data on what trout in the wild are eating piece-by-piece.

Your theory on spawning is also of limited usefulness. You are trying to force trout into some basic evolutionary theory you have hatched rather than take what we know about the fish and use it. For example, in salmon and in trout studies show that precocious smaller males sneak in and fertilize the eggs and they are extremely efficient at it. Check the literature. The theory of what is a dominant male or who wins the mate is more fiction often times than scientific fact.


That wasn't really a "theory on spawning." Look back at what I wrote -- I was just using it to illustrate one of many possible competitive advantages held by the competitor in the best physical condition. If you're denying that faster growth and larger energy reserves usually give a competitive advantage, then you're in opposition to most of ecology.

I think you eventually come to the conclusion that your theory needs more work.


I've never denied that it needs more work. Everything in science needs more work. That doesn't mean the basics aren't right. I think my main idea -- target fixation as a means of increasing long-term average energy efficiency -- is very sound and you haven't made much of a case against it yet.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Shawnny3October 13th, 2007, 6:51 am
Moderator
Pleasant Gap, PA

Posts: 1197
Wow, you guys have gone a long way before I've had a chance to weigh in - a tall feat and probably a good thing. I've enjoyed barely keeping up with the posts. Smallstream, it's now clear there was no need to apologize for your first post - it's a great topic and a great forum to ask it on.

I only had a few things I wanted to say, and most of them have already been said better by others (and then quickly refuted). I just wanted to add a point about opportunistic feeding. I think that trout, when we think they're feeding opportunistically, sometimes may just be acting out of curiosity. Fishermen often have great success on certain brightly colored flies that are not at all imitative, probably do not trigger aggressive responses, and do not offer a particularly large intake of calories. Why do the fish strike them then, even when 'fixated' on something else? Maybe they're just being curious.

Though I have absolutely no scientific evidence for it, I think fish might use their mouths as we use our hands - to feel stuff. I think a lot of animals do this (as does my 10-month-old son!), and I think fish might do the same. This is significant to the fisherman because we usually assume a fish is trying to eat the fly we just used to catch it, when really it may have had no real intention of eating it at all - it's just using its mouth to check it out. This is not to say the fish is feeding selectively or not selectively, it just complicates matters. This idea does influence my tying, though - I often try to develop patterns (and many others do this as well, perhaps without really stopping to think about why) that capture the attention and curiosity of the fish, flies that do things just a little differently from other naturals and artificials they see on a daily basis. I don't know if trout curiosity is responsible for the effectiveness of these patterns, but they can be consistent producers and, sometimes, lucrative producers.

To continue this idea, because trout have no other real means of "feeling" debris floating by, it is not crazy to think that they might have a powerful sense of taste. Again, you guys could probably comment on this a lot more knowledgeably than I can - I just bring it up as a possibility. Do sulphurs and some types of midges just taste really good, as some have posited (perhaps facetiously) before on this forum? Maybe that's why they're taken over the drakes. Just a thought - please correct me if I'm way off.

I like a lot of what Jason has said, but the idea that fish are simply conditioned for efficiency (albeit imperfectly) I'm not sure I buy into. Why do some fish expend so much energy on inaccurate rises, flipping two feet out of the water to slap haphazardly at dries? Even foraging animals exhibit "play" behavior, some of which could be construed I suppose as exercise or training for future battles, but sometimes I think it may just be play for the sake of playing. Animals exhibit this behavior when energy sources are abundant and they don't have to worry too much about being efficient. So I think there's a limit to the ideal of efficiency - when you have abundant food, you can afford to fool around. The big, lazy fish who eats a sucker every three days decides to spend his leisure time safely tucked away under a rock, while the little 6-incher slaps at dries out in the middle of the pool.

There's been a lot of disagreeing on here, but I think that may be more a function of people's trying to sum up in 50 lines ideas which really require 500 lines than of people really having drastically different opinions about trout feeding behavior. Personally, I'm trying to use the counterpoints as a way to clarify ideas and synthesize an overall better understanding for myself. I appreciate everything that's been said - my thanks to all who have posted.

-Shawn
Jewelry-Quality Artistic Salmon Flies, by Shawn Davis
www.davisflydesigns.com
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