Odds of a Wild Tiger Trout reaching 6”

[Prospector]

I didn’t want to hijack the thread on Catching the Wild Grand Slam, so I opened a new one.

The Odds of a Wild Tiger Trout reaching 6” can be computed using some available data but it also requires making assumptions about things that aren’t very concrete. Obviously this is all up for debate and I’m curious if you would change the assumptions.

Here’s my guess

What are the odds of a hen brown trout choosing a buck brook trout as a mate. Not sure how to quantify, but let’s say 0 to 3 pairs per watershed. The smaller the creek the smaller the chance. For purposes of the calculation, I’ll guess 1 mixed breeding pair on the stream every year.

The average brown trout lays 900 eggs per pound. In a wild trout stream let’s assume the hen brown weighs 1/2 pound and lays 450 eggs.

Some eggs will be consumed by fish, aquatic life, birds or mammals. I’m guessing 30% loss. That leaves 315 eggs that reach maturity in terms of days.

Hatchery success using brown trout eggs with brook trout milt is in the 5% range. The hatchery can increase those odds up to 85% success by artificially introducing a heat process that wouldn’t happen in nature. So out of 315 eggs, 16 hatch.

In the Alevins and Parr stage, many will be consumed by fish, other aquatic life, birds or mammals (typical losses are 95% as reported by trout organizations). Out of 16 Alevines, statistically 0.8 make it to a fingerling.

What is mortality from fingerling to a 6” Trout? I’m guessing 50% minimum but the real number could be as low as 10%. I’ll go with 30% so that calculates to 0.24 or 1 wild tiger trout every 4 years grows to a reasonable size in that stream.

The big variable that is hard to quantify is “What are the odds of a hen brown trout choosing a buck brook trout as a mate”. If that only happens once every 4 years, the stream would produce 1 wild tiger trout every 16 years.

As Wildtrout2 said in the other thread, catching that unicorn of a trout is another miracle.

Frank Nale, you probably have the best data of anyone in the state. Do you have any data that suggests the total number of trout you have caught from streams that exclusively have wild brown and native brook and how many wild tiger trout from those same streams. I’m guessing it’s in the neighborhood of 1 tiger trout for every 30,000 to 50,000 browns/brook

 

[theoriginalnickyp]

Very interesting, is "choice of mate" important to insemination of an egg? Seems like a spunky brook trout could just drop some milt on a red and that would increase probability from your model.

 

[wildtrout2]

That is interesting, thanks for taking the time. Looking at those numbers, I'll stick with my thinking that catching a wild tiger trout is equivalent to hitting a lottery.

 

[troutbert]

I've caught a few wild tiger trout, and saw a friend of mine catch one. The first time it seemed like a big deal to me.

But after that, not so much. I don't know why people make a big deal out of them. They aren't much to look at. And catching one doesn't give you any information about trout populations.

I get more excited about catching a 10 inch native brookie than catching a tiger trout. If you fish a stream and catch a bunch of 8 inch brook trout, and maybe a 9 incher and 10 incher, that tells you that the brook trout population is doing pretty well in that stream, which is a very positive thing.

Regarding the adds of catching a tiger trout. If you fish freestone wild trout streams a lot, you'll probably eventually catch a tiger trout.

 

[rrt]

Agree w/ t/bert. I've caught only a few wild tigers over many years, but if you fish enough times on wild trout streams that contain both native brook and wild brown trout, you are likely to eventually catch a few.

 

[wildtrout2]

troutbert wrote:


I don't know why people make a big deal out of them.

Perhaps their rarity? :-D

 

[Swattie87]

They’re not that common, bottom line. I fish the types of streams you’re most likely to find them in (small, forested freestone streams) a lot. I’ve caught one. Coincidentally, this same fish, confirmed via photos, was caught by salmonoid a few months later and a few hundred yards downstream from where I caught it.

I lost at my feet a second fish I was pretty sure was a Tiger. And I was witness to Sasquatch catching one. But that’s it. I’d estimate I catch on the order of 1000 or so wild Trout/year, and encountering a Tiger is about a once every 5 year occurrence based on the rate I’ve seen them. I’d say 1 out of every 5000 wild Trout is a reasonable rough approximation from my perspective.

Though he fishes with spinners, I agree FrankTroutAngler likely has some detailed statistics on this type of thing. His data set is far larger than mine, and it’d be interesting to see what his Tiger rate is. Whatever it is, I think that’d be pretty accurate. Or as accurate as you’re gonna get anyway. Hopefully he sees this thread.

 

[Prospector]

theoriginalnickyp wrote:
Very interesting, is "choice of mate" important to insemination of an egg? Seems like a spunky brook trout could just drop some milt on a red and that would increase probability from your model.

This is an interesting thought and one that exceeds my knowledge. However let’s assume that fertilizing fish eggs is the same as human eggs where 2 people cannot fertilize the same egg. Something happens to prevent that. However since a fish fertilizes many eggs at once there is a very good chance that some eggs laying in the gravel are not fertilized and a “passerby” could give them a spray on the way past or mating pair of 2 brook trout could use the same gravel after 2 browns laid there eggs.

Someone had a post a in Nov where he saw several pairs using the same gravel on Spruce Creek at the Tepee.. I think it was brown, rainbow and brook.

Again this is just a guess but I imagine the sight of a hen brown doing her thing is what triggers the release of milt and not the sight of a random set of eggs laying in the gravel. Probably the more likely fish response to seeing an egg would be to eat it.

 

[Dave_W]

I'm convinced that - to the extent that one can even get a picture on such a rare occurrence - that wild tigers are more prevalent in NC PA than down here in my neck of the woods.

Anyway, another possible factor impacting this might be the locations in a stream where BTs and STs spawn. I don't think I have ever seen STs and BTs spawning on the same gravel (in Big Spring it is common for STs and rainbows to spawn on the exact same redds or gravel). However, in streams with good populations of both species and with some good sized STs combined with limited sand/gravel. . . it seems plausible to me that these sites would be more likely to be used by both species. Combine this with a year with some sort of weather anomaly that has STs spawning later or BTs earlier. . . such variables could increase the probability of producing tigers(?).

As for growth rates, I would think a wild tiger would reach 6" something like mid-way between the growth rate for STs and BTs in that watershed in the same time frame. Perhaps they might grow a bit faster than STs and maybe as fast as BTs due to hybrid vigor(?).

As for probability of reaching 6" - possible variables that might also affect this could be the time the fry swim up in spring and the ratio of adult BTs vs. STs in the stream. Streams with higher ratios of BTs could increase predation and decrease the survival odds for our fingerling tiger.

Fun stuff to think about.

 

[FrankTroutAngler]

This topic was discussed a couple years ago in the link below. For those of you new to the board, you may want to go back and read it. There are many photos of wild tiger trout in it. This topic pops up once in a while and it is one of the more interesting topics, at least to me.

You may find Mike Kaufmann's (retired Area 6 -- SE PA -- PFBC Fisheries Manager) post that includes electro-shocking data particularly interesting on page 4.

Keep in mind that my home range is the central corridor of the state, from Bedford County in the south to Potter County in the north.

Chances for a wild tiger trout

Prospector asked the following question in his original post:

"Frank Nale, you probably have the best data of anyone in the state. Do you have any data that suggests the total number of trout you have caught from streams that exclusively have wild brown and native brook and how many wild tiger trout from those same streams? I’m guessing it’s in the neighborhood of 1 tiger trout for every 30,000 to 50,000 browns/brook."

To answer this question accurately I would need to take the total number of trout I've caught in the last 42 years (1979 - 2020) and subtract all of trout I've caught from streams holding only wild brown trout so that my denominator includes trout only from streams holding both native brook and wild brown trout. The problem here is that I don’t have a running tally by stream for the last 42 years. It would probably take me a week to add and double-check all of those numbers. Perhaps I could send the raw data to one of you and you could add it up for me? (Yeah, you’ve got to admit that’s funny.)

I’ve caught 23 bona fide wild tiger trout in my life so I know the numerator (23 / ???,???).

Anyway, let me pretend I’m a Great Blue Heron and take a stab at it. I’ve caught 315,258 trout in the last 42 years. Since there are people on this board who do not know me, below is a section I put in my year-end trout fishing summary that I post annually on my Facebook page, “Frank Nale.” If you know me and believe my statistics, please don’t waste your time with this section.



“In this summary I will be mentioning numbers of trout caught and other statistics. This is not meant to be bragging but to give you a factual account of my fishing adventures. If this offends you, please read no further. If you choose to continue reading, I can assure you that my numbers are perfectly accurate. I carry a small tablet and pencil with me while fishing. When I get to a stream I write down the date, stream name and section, color of spinner, time, and the air and water temperatures. While fishing, I count only trout that I have hooked, played, and landed. “Long releases” are not counted.

After catching and releasing a trout, without exception, I get out my tablet and record the size, species, and time-caught before making my next cast. This process takes only seconds and eliminates any chance of double-counting. I accurately measure my trout by holding them parallel against the grid of inch-marker thread-wraps that I put on my custom-made spinning rod. When necessary, I round the size of my trout down to the nearest one-half inch. When I finish fishing for the day I calculate the hours that I have fished to the nearest one-fourth hour. I also try to quit on or very near to one-fourth hour increments. I do not count time spent taking photographs or chatting with other anglers as fishing time. All of my fishing is done in streams that are open to free public angling.

Despite all of the effort that I put into maintaining the integrity of my data, people often question how I can have a day where I catch trout, for example, at an average rate of fifteen per hour. Their reasoning seems to be that there is just not enough time in an hour to hook, play and land fifteen trout, much less have time to move from pool to pool and do all of the other things necessary to a catch trout.

Well, in reality it does not take all that much time to catch fifteen trout in an hour. On a large stream it takes me, on average, no more than thirty seconds from the time I hook a trout until the time I am ready for my next cast. I have been timed. On a small stream this time would be substantially lower. If I spend thirty seconds on each of the fifteen trout that I catch in an hour, this means that I spent all of seven and a half minutes on the actual process of catching those fifteen trout. This leaves over fifty-two minutes per hour to do all of the other things necessary to catch trout.

My all-time best hour is 77 trout, so this should show you how much time remains in an hour after just fifteen trout are handled.”



From the total of 315,258 trout we can immediately and accurately subtract 103,176 trout because I do keep a running tally of how many trout I’ve caught on my top stream, a wild brown trout fishery. I’m now down to 212,082 for my denominator.

From here I have to make estimates. I’d guess that I’ve caught about 50,000 trout from two of the larger streams that I fish. I’m now down to about 162,000 trout.

Next I back out the trout from a bunch of small limestone streams that hold only wild brown trout. I’d guess this total to be about 40,000 trout. I’m now down to an estimated 122,000 trout.

Lastly, I have to back out maybe 7,000 trout from miscellaneous streams, such as those that hold only wild brown trout and stocked trout, as well as those that used to or currently hold only native brook trout. This leaves me with a denominator of 115,000 trout caught in streams that hold both native brook and wild brown trout. I want to stress that this is strictly an educated guess. Maybe one of these years I’ll add up all of the trout I’ve caught by stream and do this more accurately.

So, 115,000 trout caught in streams that hold only native brook and wild brown trout divided by 23 wild tiger trout equals one wild tiger trout for about every 5,000 trout caught.

Interestingly, this matches Swattie87’s guess of 1 : 5000. This doesn’t make me or him right, but I think it gives you a pretty good idea of the probability of catching a wild tiger trout.

A couple other tidbits:

1) The stream where I caught my first tiger trout (Mifflin County) I have fished only once and probably didn’t catch more than a dozen trout that day.

2) Two of my 23 wild tiger trout were very likely the same fish. The first time I caught it (autumn) I also caught a native brook trout, a wild brown trout, and a stocked rainbow trout in the same small pool way up in the mountains. I caught it again the following spring in the same pool.

3) As mentioned in the link provided at the beginning of this post, I’ve caught almost all of my wild tiger trout in streams that hold only a token population of wild brown trout.

4) Also mentioned in the link provided, one of the wild tiger trout I caught in Blair County was also very likely caught about a month later by KenU, a regular on here. Interestingly, someone posted my photo of this small trout (maybe 6”) with a #10 treble hook in its mouth on a Washington State fly fishing site and a bunch of the guys there immediately said that trout was as good as dead.

5) We all are fascinated by different things, and that’s okay. A couple of the people on here have said that catching a wild tiger trout is no big deal to them. Personally, I think they are beautiful and when I catch one it makes my day. I would rather catch a 5” wild tiger trout than an 18” wild brown trout or an 11” native brook trout because they are rarer.

6) As noted in the link provided, I once caught two small different wild tiger trout within a couple minutes of each other. I’ve caught 6 or 7 of them in this small stream out of maybe only 1,500 trout. My brother also caught one there while fishing with me.

7) On one very tiny stream I’ve caught two wild tiger trout about 35 years apart. My total trout caught on this stream is probably no more than 200.

- Frank Nale -

 

[Swattie87]

Good info, thanks Frank. Glad you saw the thread.

I didn’t back out in my rough math above the fish I catch from streams that only have Browns or Brookies, but should have.

I fish mostly small wild Trout freestoners that have both, and the vast majority of the fish I catch come from watersheds capable of producing a Tiger, but I do fish some central PA limestone streams that only have Browns, and some coal country streams that only have Brookies (for now) a handful of times/year. Accounting for that, my rate may be more on the order of 1 in roughly 4000 to 4500, but still roughly in the same ballpark for estimating purposes.

 

[Prospector]

Frank,

Thank you for providing all of those details and obviously your data is tremendous. Your point #3 strikes me as a key element for anyone with a lifetime goal of catching a wild tiger trout.

You wrote: 3) .......I’ve caught almost all of my wild tiger trout in streams that hold only a token population of wild brown trout.

In my original post I wrote: The big variable that is hard to quantify is “What are the odds of a hen brown trout choosing a buck brook trout as a mate”.

Well the answer is obvious...it’s when male Brown trout are not readily available so the hen brown settles for a brook trout. It just makes so much sense when you can evaluate 23 occurrences.

Frank, I knew you were key to this discussion and I appreciate you sharing. Also I think it’s great that you and Swattie line up at 5000 wild brown and brook caught for every wild tiger. I had that number 6x to 10x higher. However with the added knowledge that an angler can target streams where brook trout are dominant with just a smattering of browns, you can up your odds significantly.

Very interesting.

 

[wildtrout2]

The smattering of browns concept certainly applies to the stream I caught my only wild tiger on. I'd fished this stream for about 6 years and only ever caught natives, until I caught the tiger. I thought it was very odd, because I had never seen a brown, let alone caught one, thus far.

I went another several years before catching my first wild brown. It was actually pretty decent at 11". I've since only caught 3 other browns. I just find the wild tiger trout thing fascinating.

 

[Prospector]

Mike’s data from SEPA has 5 wild tiger trout found over 42 years of electro shocking when 93,000 wild brook and brown were found. So that is 1 wild tiger trout for 18,600 wild brown/brook combined.

 

[afishinado]

Prospector wrote:
Mike’s data from SEPA has 5 wild tiger trout found over 42 years of electro shocking when 93,000 wild brook and brown were found. So that is 1 wild tiger trout for 18,600 wild brown/brook combined.

That high number makes sense since a lot of the wild tigers caught as detailed by Frank and others were actually the same fish caught multiple times.

So if the numbers hold true the odds of catching a WTT is 1/5,000, and that's only if fishing in certain streams.

I would guess the actual numbers of fish out there are far less, more like Mike's numbers.

 

[troutbert]

Prospector wrote:
Mike’s data from SEPA has 5 wild tiger trout found over 42 years of electro shocking when 93,000 wild brook and brown were found. So that is 1 wild tiger trout for 18,600 wild brown/brook combined.

That data probably includes many streams that hold only brown trout, or only brook trout. Such streams have zero chance of producing tiger trout.

Frank's estimations tried to include only streams with mixed populations, which is the logical thing to do.

For streams with mixed populations, the 1 in 5,000 ratio seems like it is probably "in the ball park."

 

[FrankTroutAngler]

afishinado wrote:

Prospector wrote:
Mike’s data from SEPA has 5 wild tiger trout found over 42 years of electro shocking when 93,000 wild brook and brown were found. So that is 1 wild tiger trout for 18,600 wild brown/brook combined.

That high number makes sense since a lot of the wild tigers caught as detailed by Frank and others were actually the same fish caught multiple times.

So if the numbers hold true the odds of catching a WTT is 1/5,000, and that's only if fishing in certain streams.

I would guess the actual numbers of fish out there are far less, more like Mike's numbers.

Only one of my 23 was caught twice by me and included in my stats twice as far as I know. I didn't mention this before, but I also hooked one that was about 5" many years ago that actually jumped out of the water and onto the bank on the other side of the stream. Its mint-green color was distinctive so I know it was a wild tiger trout. The water was too deep for me to wade over to it but it flopped into the water within about two seconds. So...even though I obviously didn't count this one, it kind of makes up for the one that I caught twice and counted twice.

 

[Prospector]

troutbert wrote:

Prospector wrote:
Mike’s data from SEPA has 5 wild tiger trout found over 42 years of electro shocking when 93,000 wild brook and brown were found. So that is 1 wild tiger trout for 18,600 wild brown/brook combined.

That data probably includes many streams that hold only brown trout, or only brook trout. Such streams have zero chance of producing tiger trout.

Frank's estimations tried to include only streams with mixed populations, which is the logical thing to do.

For streams with mixed populations, the 1 in 5,000 ratio seems like it is probably "in the ball park."

Troutbert,

Thanks for pointing that out. I had intended to highlight some past comments that alluded to wild tiger trout being more prevalent in NCPA and CPA, probably for the reason you point out. However the ST numbers that Mike cited are higher than I expected for that region.

But only 5 wild tigers in 42 years is a surprise. That implies that if an angler fished the same places and for the same amount of time the electro shocking team worked the area, that angler would be within catching distance of a wild tiger trout once every 8 years.

 

[KenU]

About 20 years ago I was fishing Spring Creek just above the old abandoned hatchery, above the Paradise. It was late in October and the browns were starting their spawn. I had just starting for the day and saw a female brown about 16 inches long excavating a redd. She was being attended by a smaller brown about 12 inches long. He was hanging out a foot or so downstream below her.

To my amazement there was a good sized brookie, maybe 10 inches long, hanging out about a foot from and alongside the hen brown as she was digging the redd. Whenever she would squat on the redd he would rush over beside her and the male brown would dart up and chase him away. This went on for about a half hour before I tired of watching the whole affair and went on upstream to fish. I never knew the outcome of all this. I have no idea where that brookie came from or whether he got a chance to dart over and fertilize some of the hen brown’s eggs, but he was sure trying. I might add I have never seen or caught a brookie in Spring Creek, but he was there. And that’s how tiger trout happen.

And Frank: I bet I know where you caught that tiger trout you refer to. It’s a small trib to a trib of the Little J. It was a bit bigger than 6 inches though and it wasn’t caught on a treble hook. I got it on a dry #14 Adams. How in the world did you ever know about that fish?

 

[FrankTroutAngler]

KenU wrote:
About 20 years ago I was fishing Spring Creek just above the old abandoned hatchery, above the Paradise. It was late in October and the browns were starting their spawn. I had just starting for the day and saw a female brown about 16 inches long excavating a redd. She was being attended by a smaller brown about 12 inches long. He was hanging out a foot or so downstream below her.

To my amazement there was a good sized brookie, maybe 10 inches long, hanging out about a foot from and alongside the hen brown as she was digging the redd. Whenever she would squat on the redd he would rush over beside her and the male brown would dart up and chase him away. This went on for about a half hour before I tired of watching the whole affair and went on upstream to fish. I never knew the outcome of all this. I have no idea where that brookie came from or whether he got a chance to dart over and fertilize some of the hen brown’s eggs, but he was sure trying. I might add I have never seen or caught a brookie in Spring Creek, but he was there. And that’s how tiger trout happen.

And Frank: I bet I know where you caught that tiger trout you refer to. It’s a small trib to a trib of the Little J. It was a bit bigger than 6 inches though and it wasn’t caught on a treble hook. I got it on a dry #14 Adams. How in the world did you ever know about that fish?

Hi Ken,

Stocked brookies were very common in Spring Creek in the autumn of 2004 due to Hurricane Ivan flooding out the Benner Spring Fish Hatchery, particularly in the stretch above Fly Fisherman's Paradise and up to the Benner Spring Fish Hatchery. If by chance this was the year you saw the brookie on Spring Creek then it almost for sure came from the Benner Spring Fish Hatchery.

If the year you saw it was not 2004 then I would say it was just an escapee from the BSFH.

The wild tiger trout I mentioned above that I believe you also caught was caught by me on 5/23/15. It was 6.5" long. This was my 20th lifetime wild tiger trout.

Coincidentally, my 19th lifetime wild tiger trout was caught on this same stream within probably fifty yards of where I caught this 6.5"er. This 19th wild tiger trout was 4.5" long and was caught on 5/15/11.

The reason I know about you catching what was probably the same wild tiger trout that I caught on 5/23/15 is that you told my brother Mark about it and he told me. Assuming you caught it within a month or so after I caught it my guess is that it couldn't have been much more than 7" when you caught it. If your wild tiger trout was, say 8", then I would say you likely caught a different one.

I may not have been very clear above when I wrote about the wild tiger trout with the treble hook in its mouth. The photo that I spoke of is a photo I took of the 6.5"er I caught. This photo is in the link I posted above. I think everyone knows you wouldn't have caught a trout with a treble hook and I hope no one thought I was implying that.