Shocking And Results?

[Brian Wise]

Ok guys, help me wrap my tiny brain around something.....

MDC (and Justin) shocked the NFOW earlier this month and the fish they counted had their tails clipped so they wouldn't be counted a second time during the next shocking.........we have caught a TON of fish since the shocking and only 1 of those fish had their tail clipped. It is obvious that the numbers aren't meant to be "exact" but does MDC add a certain percentage of "missed fish" to their numbers or do they go with the exact numbers they actually shock, measure, clip, and release?

[Al Agnew]

Nope, I believe they have formulas for estimated total population compared to how many they shock up. And a lot depends upon water conditions at the time of shocking, because certain water conditions make it more effective than others. Mainly, too, shocking each year at a certain time means they can compare from year to year, rather than just making one shocking run and then saying the river has X number of fish in it.

[Outside Bend]

Ok guys, help me wrap my tiny brain around something.....

MDC (and Justin) shocked the NFOW earlier this month and the fish they counted had their tails clipped so they wouldn't be counted a second time during the next shocking.........we have caught a TON of fish since the shocking and only 1 of those fish had their tail clipped. It is obvious that the numbers aren't meant to be "exact" but does MDC add a certain percentage of "missed fish" to their numbers or do they go with the exact numbers they actually shock, measure, clip, and release?

They make a population estimate based upon the number of fish they initially marked, and the number of fish they subsequently recapture. I'm notoriously bad at math, and couldn't accurately cut and paste it, but here's an explanation and some examples of the math involved:

http://www.dnr.state.mi.us/publications/pdfs/IFR/manual/SMII%20Chapter07.pdf

[Gavin]

They dont get them all...say they sample 100 on day one...and capture 100 on day two, with a 30% recapture rate...using the math in Tom's link...it comes out to an estimated population of 329 fish per mile...of which 100 fish were marked....

{(#Sampled Day 1 + 1)x(#Sampled Day 2 + 1)}/(# of fish Recaptured on Day 2 + 1)=Total population estimate.

When we did the Current, or recapture rate was around 40%, but its skinnier water and easier to sample. Cheers.

[Wayne SW/MO]

Color me a skeptic, but I can't wrap my mind around the the claim that they can estimate he number of fish through shocking. I have no doubts about claims of condition and growth, but I don't see how they can get beyond a claim that there is a reasonable population or not. I would think angler surveys would produce better results because of the longer period of time involved.

[snagged in outlet 3]

Color me a skeptic, but I can't wrap my mind around the the claim that they can estimate he number of fish through shocking. I have no doubts about claims of condition and growth, but I don't see how they can get beyond a claim that there is a reasonable population or not. I would think angler surveys would produce better results because of the longer period of time involved.

That may be true Wayne but how do you account for angler exageration and flat out lying????

Tha math to determine real catch rates based on angler surveys has to be extremely complcated and exhausting?? And I thought Quantitative Chemical Analysis was a hard class in college.

Pete

[Brian Wise]

Makes sense....and I figured that was the case. We just simply don't catch 'that' many fish that have their tail clipped after MDC shocks, and lets face it we see one or two fish caught through October.

[Justin Spencer]

I think only 10% or so are shocked on this river. Recapture allows you to extrapolate from the total sample the population estimate and it is only an estimate for sure. Common sense says if only 10% of the fish caught the second day are recaps, then the first day you probably only captured 10% of the total population. That is an extremely crude estimate and I'm sure MDC has a more complicated formula, but it's really pretty simple. More importantly if they sample the same way each year they can look at population trends which is probably more important than the estimate itself.

[Wayne SW/MO]

That may be true Wayne but how do you account for angler exageration and flat out lying????

Tha math to determine real catch rates based on angler surveys has to be extremely complcated and exhausting?? And I thought Quantitative Chemical Analysis was a hard class in college.

Pete

I believe that in most surveys of this type the eliminate the edges. The exaggerators or the poor fishermen wouldn't then skew the results. I don't remember averaging being to complicated, even for me.

I would like for them to use something on the level of average success or reasonable limits of success to describe the stream. Lets face it, we only care about estimated, think guess, numbers because we think high ones will mean a better chance of sucess, but that's not always true.

[Justin Spencer]

I'll give you that estimate. The average fisherman on the NFOW fishing on their own will catch an average of 3 fish in a day. If that does not discourage you and you come back again you will catch a few more fish next time hopefully. This has nothing to do with population and everything to do with a different type of fishing than most are used to. People who have been fishing here for years and do it right might catch between 10-20 fish in a day. I still go out and have days where I catch very few, just the nature of this river. Part of what makes it so tantilizingly frustrating, and also keeps the Orvis hatch down.

If you call me and ask if the fishing is good or bad I'll tell you the truth. And part of the truth is that the fish can be biting good and experienced fly fishermen still can get skunked here. That being said, if you can mend well (more important than casting here) and you put on enough weight, you should catch a few if you are fishing the fast water.

Too many factors go in to expected catch rates to make them a good measure of anything.