# Discovering - (Coasters) DNR Electrofishing



## PunyTrout (Mar 23, 2007)

Here is a segment on electrofishing for Coaster Brook Trout in the UP. @B.Jarvinen might dig it.







I think I'll withhold my comments for a later date. (If, at all.)


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## bigmac (Nov 28, 2000)

I was "shocked" at the handling of the fish! First they are electrocuted, scooped up scraped by a pair of scissors for a scale, then half of their jaw is cut off. *I understand it's for science*....but then those fish were just thrown back into an inch of water!!!! I just thought they would have treated them a little more gingerly on the release after all that...dang why don't they give em an anal probe while they are at it????
and no Im not some hippie tree hugging sissy. I kind of understand why there are no coasters with the way they got their fins kicked in that video....Hell, I bet half those fish die after all that.


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## summer_doug (Dec 30, 2016)

bigmac said:


> I bet half those fish die after all that


It sure did seem really brutal.


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## MrFysch (Feb 9, 2008)

Not a single coaster surveyed from what I saw....very sad with all the effort put into bringing them back.


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## B.Jarvinen (Jul 12, 2014)

Yeah, Troy sent me a link to that several days ago. I have been compiling a spreadsheet of my Brook Trout fishing results for him even though I don't fish any of the actual BTRA streams with the special regs, just for more comparison data. I believe he is just starting on trying to survey people who fish the adjacent shallow waters of Lake Superior - surely they should turn up a Coaster once in a while?

But OMG OMG, he named THE Coaster River in Michigan, like every other web resource on this subject ever - should we delete the thread?

I don't think the handling techniques were all that stressful. This was filmed in the Fall, obviously; Trout are more stressed by catching them in hot weather, and far more stressed after being caught by hook-and-line than this shocking technique. I don't think the fine points of careful C&R are as important here.

I did think it was cool they would both be able to confirm a fish having lived in Superior via chemical analysis of those clips they were taking. It is also great that they will be correlating age from scales, to size of fish. Minnesota published a good look at that after a 2013 study, I am looking forward to an update on their data someday. I think one reason it is pretty hard to find Brookies in the 14+ class in a stream is that a 10+ Brookie is likely a third year fish, and there just might not be a real good chance they can make it to four years in a small stream. Just a personal hunch that I hope to learn more about.

And there weren't any Coasters in the video. The video does reveal a prime reason it is harder to find a Coaster - competition with Coho and Steelhead, the predominant two species found via the electro-fishing. Troy confirmed for me that THAT ONE SECRET Coaster river actually does have Coho and Steelhead too, despite never being planted with either species - as does just about every single tributary to Superior aside from possibly the Waishkey, many/most without ever being explicitly planted. (Same for many Lake MI tribs).

Water temps forcing the Brookies out to the Lake - could be, could be. I am very curious lately about the return mechanism of Salvelinus (Brookies) vs Oncorhynchus (Steelies, Coho). I somewhat doubt it works exactly the same and as a fellow angler on the South Shore pointed out to me this fall - if the streams come out of the same general streak of bedrock a few miles apart, are they really going to be all that chemically different? Is the "homing" mechanism that exact? Clearly finding exotic Oncorhynchus species in so many streams where they were never planted indicates it might be a little less than precise.

So if whatever it is that forces Brookies down to the Big Lake - population pressure / food competition, or water temps (genetic mechanism is now a theory of the past I believe) - what would guarantee the Coaster returns to the exact stream of birth? The Minnesota study in 2013 found the beginnings of correlation to Fall water temps and return stream choice, I believe. Will have to read it again. 

Though I usually catch Coho and Rainbows when I am out hunting Brookies, I think there are far better Brookie streams, or at least Brookie reaches, than the one depicted by the camera crew. Just a tad shallow, in my opinion; too close to the headwaters to find the more delightfully sized Brookies, who are the Boss Fish in the deeper holes farther downstream. If I came up on to that reach in the video, I would fish it, sure, but I wouldn't spend much time there as I kept trekking on in search of deeper water, if it were Brookie season. Cohos are looking for gravel, not cover depth; though they are wary in shallow water, they don't avoid it routinely, either.


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## Forest Meister (Mar 7, 2010)

B.Jarvinen said:


> Yeah, Troy sent me a link to that several days ago. I have been compiling a spreadsheet of my Brook Trout fishing results for him even though I don't fish any of the actual BTRA streams with the special regs, just for more comparison data. I believe he is just starting on trying to survey people who fish the adjacent shallow waters of Lake Superior - surely they should turn up a Coaster once in a while?
> 
> But OMG OMG, he named THE Coaster River in Michigan, like every other web resource on this subject ever - should we delete the thread?
> 
> ...


Do not count out the river you excepted. Not going to tell you how I know. FM


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## Cork Dust (Nov 26, 2012)

bigmac said:


> I was "shocked" at the handling of the fish! First they are electrocuted, scooped up scraped by a pair of scissors for a scale, then half of their jaw is cut off. *I understand it's for science*....but then those fish were just thrown back into an inch of water!!!! I just thought they would have treated them a little more gingerly on the release after all that...dang why don't they give em an anal probe while they are at it????
> and no Im not some hippie tree hugging sissy. I kind of understand why there are no coasters with the way they got their fins kicked in that video....Hell, I bet half those fish die after all that.


They Should have placed those fish in a tub post-handling to recover. You *don't *squeeze a fish via a single-hand hold over its visceral cavity when marking fish. The key scale sampling area on soft-rayed fish is immediately below the dorsal fin and above the lateral line, *but hammering away *at a fish with a scissors blade is not the best way to take scales since it can also induce Saprolegnia sp. colonization. Troy Zorn and I have had a couple of marked disagreements over the years regarding study data he has been involved in. This is just one of them, since he is there to function in a supervisory capacity, as well as a researcher.

The really sad part of all this is that these streams are quite infertile, causing false annuli to form in the scale samples they are using as a means of aging the fish. They can cross-section the Maxillary bone to age the fish far more accurately.

They are using pulsed-DC current to shock those fish, as mentioned by the fish tech. interviewed. Fish have four longitudinal muscle bands, seperated by spinal column and midline, repectively. The upper two bundles are epaxial muscle groups and the lower two are termed hypaxial muscle bundles. When exposed to pulsed DC current flow in water, the epaxial and hypaxial muscles contract in a pattern that litterally compells the fish to swim toward the tip of the cathode on the hand-held probe. It is imperative that the fish not touch the probe tip, getting scooped-up prior contact. The surface area to volume ratio of a fish determines how susceptible the fish is to the current field, with smaller fish far more imperalled during capture efforts. You can dial the charge up or down, based on water conductivity values for the stream, but sometimes you end-up"frying" small fish like darters as the pop-up off bottom when exposed to the electrical field. You also capture a fair amount of giant water bugs in these streams.


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## Cork Dust (Nov 26, 2012)

B.Jarvinen said:


> Yeah, Troy sent me a link to that several days ago. I have been compiling a spreadsheet of my Brook Trout fishing results for him even though I don't fish any of the actual BTRA streams with the special regs, just for more comparison data. I believe he is just starting on trying to survey people who fish the adjacent shallow waters of Lake Superior - surely they should turn up a Coaster once in a while?
> 
> But OMG OMG, he named THE Coaster River in Michigan, like every other web resource on this subject ever - should we delete the thread?
> 
> ...


Howard Johnson and Ray White did a fair amount of work on cover preference of trout. Rainbows like lateral cover, while brook trout and browns are fish species that prefer overhead cover for holding sites.

Correlation is a measure of covariance similarity, so a positive correlation outcome does not actually infer a cause and effect relationship between the variables. Positive correlation only indicates that the variables move in-sync with each other, generally requiring other statistical test applications to determine and verify what influences the co-dependence. 

Duration of hatchery planting of coho and chinook in Superior is what drove colonization of those streams. For decades no effort was made to imprint fish to release site streams, which markedly increased straying, which usually holds somewhere around 5% during a spawning run.

Basically, what has been accepted on what constitutes a coaster is that, in years of good spawning production, there are more fish than available cover, consequently there is a cohort of fish that slowly gets "pushed" downstream and exits into the open lake environment imprinted to that stream, returning at sexual maturity to spawn.


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## PunyTrout (Mar 23, 2007)

Cork Dust said:


> The really sad part of all this is that these streams are quite infertile, causing false annuli to form in the scale samples they are using as a means of aging the fish. They can cross-section the Maxillary bone to age the fish far more accurately.


Maybe I'm under-thinking it but, some of the sampling seemed haphazard at times. Is there a risk of _cross-contamination_ with the implements being used and the samples themselves? They mentioned 'chemical signatures' to determine if a fish had migrated from Lake Superior. Can you help educate me on how this is determined?


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## Cork Dust (Nov 26, 2012)

I'm assuming they were using stable isotope analysis techniques via the maxillary bone samples they were taking to "assign" where the brook trout were living and feeding most of the time. If they were coasters that had come in to spawn, they would register with a different stable isotope signature when contrasted against the stream brook trout sampled.

Scroll down to Ecology sub-heading and read from there:

https://en.wikipedia.org/wiki/Isotope_analysis

There are now a variety of statistics driven analyses that enable fishery researchers to determine, down to species, what a fish has been feeding on, not for weeks up to a month or so, as in standard stomach content driven food habits studies, but for months. Since Great Lakes open water species move around on a near-constant basis, shifting seasonally from inshore waters to offshore locations, stable isotope signature analysis of tissues enables a researcher to essentially get an integrated signature of where the fish has been feeding over an extended duration of time, since stable isotope ratios shift both across trophic levels within the food web and depths that species "live" at for both vertebrate and invertebrate prey species. 

This technique was recently employed in a long-term analysis of salmon, trout, and lake trout food habits by the USFWS, analyzed by Matt Kornis and Chuck Bronte:

https://www.fws.gov/midwest/fisheries/fishlines-2016-07-22/feature4.html

What I find a bit odd, and problematic, is when Matt presented these data to his peers at the Great Lakes Fishery Commission's Lake Michigan Committees meeting, he presented specific data that indicate that lake trout, when they feed on alewife, preferentially consume the adult size fraction rather than the far more numerous juvenile alewife population component that all other salmonines generally consume. Since lake trout are now numerically dominant in the basin, this consumption is likely resulting in the decline in the age array of sexually mature lake trout jeopardizing the future of this sizeable segment of the forage base.

IF they were doing a population survey on brook trout within this stream, handling mortality would have to be estimated, requiring them to hold the fish sampled long enough to determine what proportion died immediately from capture and handling, which would have to be factored-into the ratio of marked versus unmarked fish via the Peterson Index. There is also a delayed mortality component that is seldom addressed...and likely heightened by the handling techniques you are witnessing. 

As several of you have noted, this ain't good science...!


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## PunyTrout (Mar 23, 2007)

Cork Dust said:


> Scroll down to Ecology sub-heading and read from there:
> 
> https://en.wikipedia.org/wiki/Isotope_analysis


Thanks for the info. Much appreciated.

Although, I can hardly tell the difference between an isotope and an isopod without my reading glasses on...


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