2006 Stocked Trout Residency Study - released today

[Mike]

Just when your minds were beginning to clear from reviewing the Wild Trout Creel Survey report and the Stocked Trout Creel Survey report here is another tome that we prepared for your consideration. You may link to the full report from the news release link provided as follows:

http://sites.state.pa.us/PA_Exec/Fish_Boat/newsreleases/2007/trout_residency.htm

Even if you don't read the full report, checking out the maps and some of the tables, especially the study waters ( all less than 15 m. wide) I think will be of interest to anglers, even those whose eyes glazed over in science class. Also, some of the habitat aspects may interest those of you who are interested in habitat in general. The topic sentences in each paragraph should do a pretty good job of telling you whether or not you want to read the entire paragraph. We had very good biometrician working on this so if it has been a while since you took your last statistics course or biometry course, this should bring back bad memories. Enjoy.

 

[Maurice]

Mike,

I am having trouble understanding the percentage of recapture. 100 fish released, 50 captured, 75 percent recapture rate adjusted.

As a coincidence today a fellow from Lebnan called me telling me I am full of it.(imagine that). He has a buddy that has no computer access and produced a report stating that 85% of trout stocked in 2004 (or 06, I cannot remember) left after high water in Lancaster...and 74% in another stream, etc. Is this the same report?

My claim was that stocked trout do a pretty good job of holding their ground. Keep in mind his experience is on Muncy Creek up North. He was disappointed that after the early stocking this season that a high water "iceout" flushed all the trout out.

This guy walks the stream driving out poachers every day. He said there were very few trout left. (I guess based on the disappearance of the goldens he could see being gone). He has a bleak outlook on the opening day.

Any insight?

Maurice

 

[Mike]

Maurice,

The gentleman may be referencing the report. Early in the tables you'll see the list of surveyed streams and the adjusted recapture rate rating of "excellent, good, fair...etc" He may have seen the table and checked out the results for his streams of interest. He then just had to look up the percentages associated with the ratings.

As for your question, which is a good one and will clarify things for the other readers, there is a recapture rate and an adjusted recapture rate IN THE REPORT ITSELF (as opposed to the news release, which I think refers to the adjusted recap rate simply as a recap rate).

The adjusted recapture rate (as it appears in the report) is the estimate of the actual number of fish that remained at each sampling site (stocking point) in the study. The initial recapture rates at each sampling site (how many of the stocked fish were actually captured) were adjusted upward by dividing the number captured at each site by 0.67, which was the average effectiveness or efficiency of the electrofishing crews in early spring (cold water) as measured before the study began. In the pre-study sampling, one electrofishing run through a length of stream one day after stocking produced an average return of 67 percent of the fish that had been stocked the day before. As you know, we don't capture 100% of the fish in a single electrofishing pass, but this way we had a good estimate of what proportion we were capturing in a single pass.

 

[ryanh]

I'm a simple man...
Where do all of the fish go? I mean I have never walked the banks in the spring and seen massive fish kills so I am left to assume that they are still alive somewhere. Do they disperse throught our waterways? If that is true than you would have a chance of catching a trout in just about any stream in the state correct?

 

[OhioOutdoorsman]

The study is very interesting.

My concerns with stocking next to wild trout are the following:

1) Stocked trout will compete with wild trout for food
2) Stocked trout will compete for lies and spawning habitat
3) Larger stocked trout (browns in particular) will each juvenille wild trout and eggs
4) Stocked trout will breed with wild trout and dilute/change the genetic diversity of the wild trout population.

If the fish do not disperse, then all of these fears are abated. If the PFGC monitors this behavior and uses it to guide how close they can stock next to wild trout populations, kudos to the PFGC.

Furthermore, I found it interesting but have not fully digested the parts on the study on stream habitat on dispersal. This may be a way for local TUs and other groups to minimize the effects of stocking on neighboring wild populations. It seams, at first glance, that the variance in dispersal was only weakly correlated with measured habitat charateristics?.....

Just from my experience, I see large pods of stocked trout all year round in some locations.....

 

[Maurice]

ryanh wrote:
I'm a simple man...
Where do all of the fish go? I mean I have never walked the banks in the spring and seen massive fish kills so I am left to assume that they are still alive somewhere. Do they disperse throught our waterways? If that is true than you would have a chance of catching a trout in just about any stream in the state correct?

Ryan,

They typically go downstream...that is why the downstream reach or river miles typically had more favorable results.

The guy I talked about said he talked to a fellow from the Conowingo Dam on the Susky at MD line and said while watching the shad come up through the ladder cameras, he would watch brown trout going down. Not just one or two either.

Using the data from the article of 259 streams, 177 had fair, good or excellent residency. Thats 72% which falls just below the (good) rating. This is the glass half full scenario.

The GHE paints a different picture. Taking the Fair rating (40-74%) residency and lumping it with the poor and very poor indicates 56% of the time the trout leave their stocking point.

And the fact that they cannot come to any conclusions as to why is the trout are leaving on a statewide basis is astonishing to me...Maybe it is because the streams have different dynamics and need to be managed differently...even if that means stocking at different times. , closer to the season, etc.

I mean come on, you telling me with 65 pages of a reports with like 8 shotgun targets in it. ( I liked those ones) :lol: The only conclusion is. (we are pleased with the result)

People should catch trout? lets hope so.

Maurice

 

[ryanh]

Oh, my mistake I misread the data. I gathered that the upper sections would hold more fish cause they would be of a higher gradient (more trouty water).

So if you are targeting stockies you would focus on the bottom end of stocked h2o?

 

[troutbert]

I see that one stream had a recapture rate (adjusted) of 180 percent. They stocked 100 trout and recaptured 121. What's the explanation? It seems pretty messy, biometrically-wise :-0

Regarding the reasons why they take off some places, my guess is that the physical reasons discussed are probably the main cause. The chute-like sections will "shoot" the trout downstream in high flow. They'll keep going until they find a low velocity area:
pools, overhead cover, tree roots, downed trees, boulders, etc. where they can find refuge from high velocity flow.

 

[Maurice]

Ryan... let me say that I got bored with comparing the numbers. what I found was 11 instances where the lower end performed better, 7 where the upper did and 7 where the were about he same.


I am sure this had alot to do with many factors regarding the streams I chose (alphabetically from A-C) Not much of a sample, I know but the very notion of not finding any overall smoking gun as to why they leave shouts individual management strategies.

 

[Maurice]

troutbert wrote:
I see that one stream had a recapture rate (adjusted) of 180 percent. They stocked 100 trout and recaptured 121. What's the explanation? It seems pretty messy, biometrically-wise :-0

Regarding the reasons why they take off some places, my guess is that the physical reasons discussed are probably the main cause. The chute-like sections will "shoot" the trout downstream in high flow. They'll keep going until they find a low velocity area:
pools, overhead cover, tree roots, downed trees, boulders, etc. where they can find refuge from high velocity flow.

TB,

I bet where the adjusted was 121 the actual was nearer to 105 or something, anyway, more were found there..and probably less in the other section. My guess is upstream.

You lower paragraph should end with.."..much like the concrete environment they were reared in."

 

[salvelinusfontinalis]

Maurice,
that fellow might not have been to far off. on first day last year i was fishing a lancaster county stream. the year before i landed over 25 trout. last year i caught 2 in 5 hrs. now while i know that doesnt mean much, im not that bad of a fisherman. i started asking around at each angler i ran into. they ALL said that they had caught either 0-1 trout. seemed unusual and then there he was, a game commission fellow. i asked him how many fish they put in.....he said quite a bit of fish. he asked why? i said i think they packed thier bags and moved away! i returned 2 times during the year to the same stream. one time was the day after second stocking. nothing was in that stream.
so my conclusion is that they either didnt put in any fish.....they didnt stock what they said.....or the fish moved down to find better water. on that report the stream got a good rating! thats bull.
try to remember that books and history are written by those who won the war. do you really think they are going to release a report saying the outlook is poor when sales are down? :-x

 

[Mike]

Sal,

What stream was that? I did the survey work in Lancaster Co and I can tell you that I did not skew the data. What we captured is what we recorded.

 

[salvelinusfontinalis]

mike,
w br octo and also experienced the same at middle ck in sub basin 7. didnt say that you skewed the data but......
data is subjective and it can say what ever we want it to. in the example where the recapture rate was over 100%. i could say that you guys didnt know how many you put in. so the data is skewed. i could say you captured wild trout. so the data is skewed. i could say that since one stream is off they all could be. who knows. i just know that if i had a hardware store and was selling snow blowers, im not going to tell people in the fall that we are going to have a mild winter!

 

[Stone_Fly]

My first though is that maybe the early opening day isn’t such a good idea, if the trout are moving as much as they do, but that's not the point, I have no reason to be critical of the data, it is what it is. No matter where I fish I here guys complaining that the fish are, too small, too few, too this, too that, etc. etc. I'd like to see an effort to identify the streams where there is a problem with stocking you’ve already started that effort and change the management on those streams. I think the study suggests that.
Now let's stop studying the movement of stocked trout and spending money on some so ephemeral and find ways to better manage something we can an impact on wild trout.

 

[vcregular]

I'd love to see some effort put toward examing the movement of wild fish in some of our larger wild trout waters, ie., Penns or Lehigh for example. I think a lot could be gained from that.

...sorry for the off topic.

 

[Chaz]

Yeah, I think it's important to the management of wild trout streams to know how the wild troutadjust to the environment where they live. I'd want Pine Creek on the list of big streams. But you see to PFBC that's not really important, because nobody fishes for wild trout.

 

[Mike]

Sal,

Thank you for the info. on the W Br. Octoraro and on Middle Creek. I belive the WCO has had some suspicions about Middle Creek. As for the electrofishing data, it certainly was not subjective. The ratings of Very good, good, fair, etc with respect to the percent recapture boundaries established for each rating were subjective, but not the electrofishing counts themselves. The counts were recorded in the field as fish were captured and we certainly did not mistake wild fish for stocked fish. In fact, my recollection is that we did not find any wild fish in the stretch of the W. Branch that we electrofished (1. about a half mile below mouth of Meetinghouse, 2. big rock area above power line). As for the site(s) where more fish were recorded via electrofishing than stocked, this is addressed in the report either in the text under sources of variability or in the recommendations. Clearly, fish could have moved into the sampling sites from upstream stocking points and there were likely some errors in counts at some sites as trout were placed in buckets to be stocked.

By the way, heron predation appeared to be very high on the section of the West Branch where we worked. One or two of the streamside landowners also mentioned that each evening and night great blue herons were working over the stream and the trout.

 

[RRR]

Mike You've finally hit the nail on the head. It's those lousy herons which cause many of the problems on both wild and stocked trout waters. Probably ought to put a bounty on them like they had on great horned owls back when I was a kid. I see no logical reason to either conserve or protect those devils. :-x

 

[salvelinusfontinalis]

suspicions about Middle Creek.

mike,

thank you for your honesty. also i never thought about fishing moving into sampling sites. good point. obviously you have and inside track and more knowledge about trout than i do. i just know how to catch them. dont think that i am picking on you or the pfbc. we all have opinions and thoughts about how things should be managed and things that should be changed. i know iam on the extreme side. i should have asked before saying anything and pointing fingers. i apologize. thank you for your insights and being so polite. hope you accept my apology.

 

[Wulff-Man]

Relax, Sal. He won't revoke your fishing license. :-D