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Species specific stocked trout residency revision

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Pcray reminded me in one of his comments that an update is in order regarding the stocked trout residency studies over the past 5 years. With well over 500 stocking points sampled, it is now clear that rainbow trout have shown significantly (very statistically significant) better residency than either brook trout or brown trout. On average, using rounded numbers for better recall, rainbow trout residency has been in the neighborhood of 80 percent while brook and brown trout residency has been cir 50 percent (brooks 48 percent, browns 52 percent). The residencies of stocked brook and brown trout have not been significantly different. While residency in any given stream may be stream specific, rainbows, when examined statewide, on average move less than brooks and browns in Pa's stocked trout streams. We are even finding that rainbows survive better in lower pH waters than we once thought. We did not used to stock rainbows at pH's less than 6.5 and we are now finding good residency in streams with pH's at least as low as 6.2. I would expect that you will be seeing more rainbows being stocked in some streams in the future. In fact, that has already been occurring in some streams for the past few years where residency of browns or brooks has been poor.

Posted on: 2012/2/15 8:21


Re: Species specific stocked trout residency revision

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Do you have any theories about why rainbow trout have better residency?

And about the cause(s) of the trout movement?

Posted on: 2012/2/15 8:49


Re: Species specific stocked trout residency revision

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Mike,

It makes sense to me that the rainbows would fair better in a lower pH setting. I would suspect that the western streams where they originated from were/are fairly acidic.

Posted on: 2012/2/15 8:52
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Re: Species specific stocked trout residency revision

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Interesting. I've always thought... and heard the opposite. In my mind, it sort of made sense based on my fishing experiences... and to a lesser extent, steelhead vs lake/ocean run brown trout fisheries. I thought of rainbows as a powerful fish built to migrate and browntrout as predators that would live in one spot their entire lives.

Posted on: 2012/2/15 8:56


Re: Species specific stocked trout residency revision
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2006/9/9 9:29
From Monessen, PA
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Trout are built to swim and to travel in streams as well as still-waters. They do not mind it at all. If sufficient nutrition exists, they will move until they find what they "are looking for." What that is, I will not tell. Really, however, I do not know.

Sometimes it is the chemistry of water, sometimes the availability of forage. Sometimes it's this one day and that another. Importantly, whether they do or do not travel is probably influenced alot by environment and just a bit by instinct. Instinct may be behind the reason for travel, or the "belief" (if you will) in the trout's mind that travel would improve circumstances, but there probably is no instinct to travel despite local conditions which satisfy all biological needs.

Posted on: 2012/2/15 9:09
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Re: Species specific stocked trout residency revision

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Yeah, based on previous studies by the PFBC, I had understood the opposite, that rainbows moved the most, followed by browns, and that brookies were the most likely to stay. But admittedly, those studies had very small sample sizes and a very small number of streams. Apparantly we're farther along with the studies, now. Thanks for the update.

The one thing that remained unchanged there is that it is very stream specific. That they show a propensity to leave some streams, and stay put in others. I've heard any number of "reasons" proposed, from water temps, pH, holding water, food availability, territorial behavior of other fish, hatchery they originated and the similarity of water chemistry with the host stream, etc. But last I knew, they were not able to really determine any of that from the limited data. Has anything changed on that front?

Also, how do you define residency? There are really 2 questions that need to be looked at. How likely are they to move? And, if they should move, how far do they go? Are we talking a few hundred yards downstream, or 10+ stream miles?

Sorry for all the questions. I don't expect you to have all the answers yet, just trying to get an idea of what has been determined. The entire topic is very interesting to me.

Posted on: 2012/2/15 9:15


Re: Species specific stocked trout residency revision

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It is apparent from our statistical scientific attempt to ferret out the causes via analysis of a multitude of variables that the reasons are complex and most likely stream and species specific. For instance, habitat characteristics accounted for only 5% of the variation. As a result, it was decided that the problem would be addressed on a stream by stream basis. One cause of poor residency in some streams is clear, however, and is probably what you would expect. Low or falling pH (to low levels) in portions of the Commonwealth that are prone to this (low alkalinities) have resulted in poor residency.

In another, more typical example, you might be surprised. As counter-intuitive as it might sound, stocked brook trout do not do well in fast moving water. They either need and seek out near-by substantial current breaks if they are not stocked directly in somewhat sluggish (eg. glides) or protected water (such as deeper pools, good pocket pools), or they move. Browns do better in that regard. Rainbows, on the other hand, will seemingly waste energy, comparatively speaking, swimming in a fast run. With the typically higher water velocities and colder water temps seen in March and early April across Pa, the stronger swimmer seems to do best. That is not to say that rainbows don't do well in sluggish streams; they do. For instance, they do very well in habitat stressed, sluggish, silty streams in Lancaster Co. They seem to have a wide range of adaptability, and that as a general statement may explain their superior performance in preseason stockings when measured across a variety of waters and stream channel features.

A personal anecdote that exemplifies the more scientific observations above is that there is a bridge over the Hockendauqua Ck in Northampton Co below which the channel configuration is such that I can readily observe the phenomenon. The bridge is over a sharp bend in the creek. The creek is stocked with all three species. The brook trout line up in the more quiescent water on the inside of the bend (where the sand accumulates). The browns are mid-channel in faster velocity water. The rainbows are lined up along the outside of the bend in the fastest velocity water.

I think the original, somewhat lengthy, report on trout residency that dealt with the variables mentioned in the first part of my response above is still available on the PFBC web site.

Posted on: 2012/2/15 9:23


Re: Species specific stocked trout residency revision

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Pcray, now you have asked a question that will also help anglers. First, let me say that the vast majority of streams that have been sampled are in the PFBC's width class 3 category....avg width 4-10 meters. Some have been larger. The trout that have "resided" have generally stayed within a stretch that is 200 m. below the stocking point and 100 m above it. Truth be told, we find very few fish upstream from the stocking points (tip # 1 for anglers). Also, we find only a relative smattering of fish 200 m. below the stocking points (often none from 150-200 m downstream, but plenty within 75 m), but that varies more than the first statement above (So that is tip #2 for anglers). When they do "run" it is almost exclusively downstream and within the first 5 days of the stocking. And, the run does not seem to stop just outside of the 200 meters. Having electrofished as much as 300 m downstream, I have not seen more fish when I have looked. Work by AFM Rob Wnuk using telemetry found that in his study stream the fish ran for miles. Some hit the Susquehanna and kept going. How far the trout are running in any particular stream once they are "willing" to go 200 m downstream from the stocking point is probably stream specific. They might stack up in better habitat; they might distribute themselves somewhat evenly, although I have not seen any evidence to support that via electrofishing, or they might "take off."

One thing that I did not mention in an earlier response to troutbert as a likely cause of the residency problem seen in some streams, especially in my region, is great blue heron predation. This was my observation early on in our residency work and later was documented in Centre Co by a PSU study of tagged stocked fish (and many tags showing up around the heron rookery).

Posted on: 2012/2/15 10:03


Re: Species specific stocked trout residency revision

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Ok, thanks, I'll have a look at that.

Yeah, in my experiences, rainbows definitely prefer faster water than the other two. You especially notice it early season, they often all move to faster water later season if the water warms as it does in most stocked streams (presumably for better DO levels). Never really noticed a huge difference between brookies and browns on that, though. You rarely find them stocked together, usually it's browns in larger streams and brookies in smaller streams, so I'm not sure I'd expect to have noticed it. Interesting, nonetheless.

Smaller streams where wild brookies are found typically may be fairly high gradient, but it's sharp riffles and slow pools, rather than a steady current throughout. And you do find brookies in the riffles, but those riffles are loaded with current breaks. Rocks, logs, etc. So I can make some sense of that.

Posted on: 2012/2/15 10:07


Re: Species specific stocked trout residency revision

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As another personal antecdote, we often fish Tionesta Creek (NW PA) early in trout season between Kelletville and Mayburg. It is not stocked with brookies, just browns and bows. We catch plenty of stocked brookies. More brookies than browns, actually, though rainbows clearly dominate. Still, catching multiple brookies happens every year and is too consistent/predictable to be merely a case of a brookie getting mixed in here and there during stocking.

The nearest stream stocked with brookies would be The Branch/Salmon Creek, which combine shortly before running into the Tionesta about 2 stream miles downstream of where we fish. The nearest upstream trib that's stocked with brookies is BlueJay, which runs in maybe 8 miles upstream. So those fish either went down Salmon and then 2 miles UP the Tionesta, or down BlueJay and then 8 miles further down the Tionesta, or else they came from tribs even further away.

Also, Salmon Creek itself. I know it is identified as a poor residency stream. My perception has been that the reason is low pH, though I've never seen that in writing. My own testing shows very low pH's, and the stream does stay cold yet lacks wild fish in an area where wild brookies are common.

But in the days after stockings on Salmon, it's mouth on the Tionesta is a fairly well known hotspot. While the nearest stocking point on the Tionesta is only 6 or 7 hundred yards upstream, the presence of brookies, and the timing suggests those fish are coming from Salmon or The Branch.

Further, later in the summer, usually June, as the Tionesta warms, the mouth of Salmon again becomes a hotspot, presumably due to cold water influence. And many of those fish do ascend the stream.

Seems logical, but I take it as confirmation that fish don't like acid, but they'll choose acid over warm water. Downstream on the Tionesta is the lake and dam, so it's not like they have anywhere to go in that direction.

Posted on: 2012/2/15 16:18


Re: Species specific stocked trout residency revision

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2007/6/19 21:49
From Lancaster County
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I used to leverage the fact that stocked brookies and brownies moved to put up some phenomenal opening day weekend numbers. My brother and I discovered this fact about ten years ago on Kinzua Creek. After the crowds thinned out, we found dozens of brookies and brownies in log jams half a mile from the nearest stocking point. It was like fishing in a hatchery (almost). I pulled three citation brookies out of these log jam setups over the years and always looked forward to fishing them. They were the type of holding water that most people would toss to once or twice and move on, but if you worked the whole thing and dunked your line in all the nooks and crannies and climbed over the whole thing, you could wrack up the numbers. The only way that the fish got there was they moved - half a mile or more. About four years ago, the lower section on Kinzua transitioned to a rainbow only preseason stocking regime. Now, the rainbows lay in the hole they are dumped in, and we don't walk as much. There are few fish outside the stocking area, unlike in years past. Some of the logjams are gone because of hurricanes a few years back.

The other data point is the year I fished a trib in the ANF of a stocked trout stream. It had at least a bucket of stocked brook trout that had made their way into it; a year later, I pulled an almost black stocked brook trout out of a hole below a waterfall that would have impeded most upstream progress of fish. I'm pretty sure it was from that initial meandering batch.

Both sets of data are purely anecdotal, but definitely support the 50% (+/-) of brookies and browns, and 80% retention of rainbows.

Posted on: 2012/2/17 21:49






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