C&R Data

Tim

Came across this researching something else. Thought you might be
interested:

https://research.idfg.idaho.gov/Fish...ticle%2013.pdf

Some different results using a different (maybe better?) methodology.
Like all fish studies, the methodology has some drawbacks but it seems
much better than the confining that the other studies used to measure
mortality in streams and rivers.

Willi

On Nov 9, 8:03 am, Willi wrote:
Tim

Came across this researching something else. Thought you might be
interested:

https://research.idfg.idaho.gov/Fish...Reports/Volume...

Some different results using a different (maybe better?) methodology.
Like all fish studies, the methodology has some drawbacks but it seems
much better than the confining that the other studies used to measure
mortality in streams and rivers.

Willi

Hi WIlli,

This was a really good read, thanks for passing it along. I agree that
there are some big question marks in the technique. The results depend
on snorkelers finding the corpses of fish that die. The control being
frozen fish anchored. Seems a little questionable to me, for several
reasons, but the results being fairly consistent with the aggregate of
other studies makes me think it's a good enough methodology. Several
things are clear. 1) Mortality is cumulative, increasing fairly
dramatically as the resource is exploited 2) It was not clear in the
study if mortality during high-stress periods such as warm water
temperatures is increased, potentially exponentially 3) Mortality from
Catch and Release fishing is, and can never be, 0. Overall, this study
suggests 3% mortality from C&R through flyfishing, in Yellowstone
park. An assumption is that differing regulations, perhaps mandatory
catch/kill/quit regulations would reduce both the overall pressure,
could target desirable classes for optimal growth, yield and health of
the fishery.

Tim

Halfordian Golfer wrote:
On Nov 9, 8:03 am, Willi wrote:

Tim

Came across this researching something else. Thought you might be
interested:

https://research.idfg.idaho.gov/Fish...Reports/Volume...

Some different results using a different (maybe better?) methodology.
Like all fish studies, the methodology has some drawbacks but it seems
much better than the confining that the other studies used to measure
mortality in streams and rivers.

Willi


Hi WIlli,

This was a really good read, thanks for passing it along. I agree that
there are some big question marks in the technique. The results depend
on snorkelers finding the corpses of fish that die. The control being
frozen fish anchored. Seems a little questionable to me, for several
reasons, but the results being fairly consistent with the aggregate of
other studies makes me think it's a good enough methodology. Several
things are clear. 1) Mortality is cumulative, increasing fairly
dramatically as the resource is exploited 2) It was not clear in the
study if mortality during high-stress periods such as warm water
temperatures is increased, potentially exponentially 3) Mortality from
Catch and Release fishing is, and can never be, 0. Overall, this study
suggests 3% mortality from C&R through flyfishing, in Yellowstone
park. An assumption is that differing regulations, perhaps mandatory
catch/kill/quit regulations would reduce both the overall pressure,
could target desirable classes for optimal growth, yield and health of
the fishery.

Tim



You need to read it again. They found mortality of .3% per capture. The
control of frozen fish were thawed and they also used gill netted fish.
These weren't anchored but allowed to drift downstream.

There were also several other studies cited that found mortality less
than 1%.

I'm involved in conducting an angler usage study for the DOW to try and
get more consistent flows in my home river. It's a project started by a
small group apart from TU, FFA etc. more of a grassroots thing. Quite a
few of the members also want to push for C&R designation for the area
involved. I'm opposed to it and I was looking up studies to bolster my
argument and I ran across this study. The biologist from the DOW met
with us last night and he's in agreement with my suggestion of a slot
limit. I think he convinced the others.

Willi

On Nov 9, 1:37 pm, Willi wrote:
Halfordian Golfer wrote:
On Nov 9, 8:03 am, Willi wrote:

Tim

Came across this researching something else. Thought you might be
interested:

https://research.idfg.idaho.gov/Fish...Reports/Volume...

Some different results using a different (maybe better?) methodology.
Like all fish studies, the methodology has some drawbacks but it seems
much better than the confining that the other studies used to measure
mortality in streams and rivers.

Willi

Hi WIlli,

This was a really good read, thanks for passing it along. I agree that
there are some big question marks in the technique. The results depend
on snorkelers finding the corpses of fish that die. The control being
frozen fish anchored. Seems a little questionable to me, for several
reasons, but the results being fairly consistent with the aggregate of
other studies makes me think it's a good enough methodology. Several
things are clear. 1) Mortality is cumulative, increasing fairly
dramatically as the resource is exploited 2) It was not clear in the
study if mortality during high-stress periods such as warm water
temperatures is increased, potentially exponentially 3) Mortality from
Catch and Release fishing is, and can never be, 0. Overall, this study
suggests 3% mortality from C&R through flyfishing, in Yellowstone
park. An assumption is that differing regulations, perhaps mandatory
catch/kill/quit regulations would reduce both the overall pressure,
could target desirable classes for optimal growth, yield and health of
the fishery.

Tim

You need to read it again. They found mortality of .3% per capture. The
control of frozen fish were thawed and they also used gill netted fish.
These weren't anchored but allowed to drift downstream.

There were also several other studies cited that found mortality less
than 1%.

I'm involved in conducting an angler usage study for the DOW to try and
get more consistent flows in my home river. It's a project started by a
small group apart from TU, FFA etc. more of a grassroots thing. Quite a
few of the members also want to push for C&R designation for the area
involved. I'm opposed to it and I was looking up studies to bolster my
argument and I ran across this study. The biologist from the DOW met
with us last night and he's in agreement with my suggestion of a slot
limit. I think he convinced the others.

Willi

You are citing the mortality rate per capture. As I mentioned this is
cumulative and increases as exploitation increases which is why they
referred to the 1981 study.

The slot limit is definitely preferable to pure Catch and Release,
which can never be justified. I really, really appreciate and respect
that you recognize this difference. As I've often stated, mortality is
not a litmus of ethicity. Of all the fish caught and released in all
studies 100% of them suffer some form of injury and stress that is
unequaled in all other man/animal relationship management.

Tim

Tim

On Fri, 09 Nov 2007 20:16:01 -0000, Halfordian Golfer
wrote:

On Nov 9, 8:03 am, Willi wrote:
Tim

Came across this researching something else. Thought you might be
interested:

https://research.idfg.idaho.gov/Fish...Reports/Volume...

Some different results using a different (maybe better?) methodology.
Like all fish studies, the methodology has some drawbacks but it seems
much better than the confining that the other studies used to measure
mortality in streams and rivers.

Willi

Hi WIlli,

This was a really good read, thanks for passing it along. I agree that
there are some big question marks in the technique. The results depend
on snorkelers finding the corpses of fish that die. The control being
frozen fish anchored. Seems a little questionable to me, for several
reasons, but the results being fairly consistent with the aggregate of
other studies makes me think it's a good enough methodology. Several
things are clear. 1) Mortality is cumulative, increasing fairly
dramatically as the resource is exploited 2) It was not clear in the
study if mortality during high-stress periods such as warm water
temperatures is increased, potentially exponentially 3) Mortality from
Catch and Release fishing is, and can never be, 0. Overall, this study
suggests 3% mortality from C&R through flyfishing, in Yellowstone
park. An assumption is that differing regulations, perhaps mandatory
catch/kill/quit regulations would reduce both the overall pressure,
could target desirable classes for optimal growth, yield and health of
the fishery.

Tim

o "anchor tags" does *not* mean the fish were fixed in place. It means that
type of *tags* were fixed in place - as opposed to the ribbon slips that were
simply passed through the gills. it is clear all carcasses used to refine the
methodology were allowed to "free-float".

o the temperature ranges that existed during the study periods are clearly
described, and the studies covered the warmest temperature periods recorded
for the sections of the river used.

o the methodology seems sound from here. of particular interest was the
avoidance of penning captured fish, as it removes the resulting stress from
the equation.

o if each fish caught has a 0.3% chance of dying as the direct result, and
each fish is caught 10 times during a season, the result is the 3% overall,
seasonal mortality rate. there's nothing "dramatic" about this; it is simple,
straight-line mathematics.

o no assumptions are provided in the study that changing the regulations -
short of banning all fishing - would improve the overall, seasonal mortality
rate.

o there is nothing obvious about a slot limit that would reduce the overall,
seasonal mortality rate. indeed, the opposite is *far* more likely: each fish
legally taken has a 0% probability of survival, while each fish released has
at least a 97% probability of survival...

cheers

/daytripper

On Nov 9, 3:22 pm, daytripper wrote:
On Fri, 09 Nov 2007 20:16:01 -0000, Halfordian Golfer
wrote:



On Nov 9, 8:03 am, Willi wrote:
Tim

Came across this researching something else. Thought you might be
interested:

https://research.idfg.idaho.gov/Fish...Reports/Volume...

Some different results using a different (maybe better?) methodology.
Like all fish studies, the methodology has some drawbacks but it seems
much better than the confining that the other studies used to measure
mortality in streams and rivers.

Willi

Hi WIlli,

This was a really good read, thanks for passing it along. I agree that
there are some big question marks in the technique. The results depend
on snorkelers finding the corpses of fish that die. The control being
frozen fish anchored. Seems a little questionable to me, for several
reasons, but the results being fairly consistent with the aggregate of
other studies makes me think it's a good enough methodology. Several
things are clear. 1) Mortality is cumulative, increasing fairly
dramatically as the resource is exploited 2) It was not clear in the
study if mortality during high-stress periods such as warm water
temperatures is increased, potentially exponentially 3) Mortality from
Catch and Release fishing is, and can never be, 0. Overall, this study
suggests 3% mortality from C&R through flyfishing, in Yellowstone
park. An assumption is that differing regulations, perhaps mandatory
catch/kill/quit regulations would reduce both the overall pressure,
could target desirable classes for optimal growth, yield and health of
the fishery.

Tim

o "anchor tags" does *not* mean the fish were fixed in place. It means that
type of *tags* were fixed in place - as opposed to the ribbon slips that were
simply passed through the gills. it is clear all carcasses used to refine the
methodology were allowed to "free-float".

o the temperature ranges that existed during the study periods are clearly
described, and the studies covered the warmest temperature periods recorded
for the sections of the river used.

o the methodology seems sound from here. of particular interest was the
avoidance of penning captured fish, as it removes the resulting stress from
the equation.

o if each fish caught has a 0.3% chance of dying as the direct result, and
each fish is caught 10 times during a season, the result is the 3% overall,
seasonal mortality rate. there's nothing "dramatic" about this; it is simple,
straight-line mathematics.

o no assumptions are provided in the study that changing the regulations -
short of banning all fishing - would improve the overall, seasonal mortality
rate.

o there is nothing obvious about a slot limit that would reduce the overall,
seasonal mortality rate. indeed, the opposite is *far* more likely: each fish
legally taken has a 0% probability of survival, while each fish released has
at least a 97% probability of survival...

cheers

/daytripper

One thing that bothered me about the study was the use of dead frozen
fish from a different waterway. Perhaps the racoons don't eat those.
The vagueries of 'finding dead fish by snorkeling' sorry but this
seems just crazy, regardless of the statistical control stated. As I
mentioned as well, this is the Yellowstone river, which has aspects
and attribution s unique to it regarding the temperature and habitat
conducive to recovery. It's also just not indicative of C&R from other
modalities, drift boat, raft, etc., nor does it account for the skill
or demographics of the participants, except to say that (I'd suggest)
folkes fishing the 'Stone are top flight with regards to education and
handling. Again, there are a lot of variabities, but the 3% seems
reasonable and in line with most of the studies which don't vary
wildly anyway, in my estimation.

Your pal,

Tim

Halfordian Golfer wrote:


You are citing the mortality rate per capture. As I mentioned this is
cumulative and increases as exploitation increases which is why they
referred to the 1981 study.

It is per capture and that seems VERY meaningful to me. If the study is
accurate, it seems that in some situations, C&R has EXTREMELY low
mortality rate.



The slot limit is definitely preferable to pure Catch and Release,
which can never be justified. I really, really appreciate and respect
that you recognize this difference. As I've often stated, mortality is
not a litmus of ethicity. Of all the fish caught and released in all
studies 100% of them suffer some form of injury and stress that is
unequaled in all other man/animal relationship management.


I'm not a fan of C&R except in some limited situations, but for very
different reasons than you. All types of regulations are tools for
biologist to manage their fisheries. Different anglers seek different
things from angling and the DOW's weigh this in making regulation
decisions. Whether "pure" C&R can be justified to YOUR mind is
irrelevant. C&R is a tool that biologists find useful in managing some
fisheries.

Personally, what I have trouble with are regulations and policies that
ignore the biology of the fishery in favor of "politics".

(Not looking to get in a C&R debate with you. Just thought you'd be
interested in some studies that show such a small mortality rate. They
were news to me.)

Willi

On Nov 9, 3:22 pm, daytripper wrote:
[snip]
o there is nothing obvious about a slot limit that would reduce the overall,
seasonal mortality rate. indeed, the opposite is *far* more likely: each fish
legally taken has a 0% probability of survival, while each fish released has
at least a 97% probability of survival...

You know better, we've been all over this. For one thing, if you had
to kill a legal fish, in a slot, and quit, there'd be a lot less
angler pressure. The quality of the experience would at once improve.
Further, the fish that remained in the system would have less
competition and watershed biomass production would be optimal. It's
also not stated, but somehow implied, that trending as close to 0
angler induced mortality through angling is even a good thing. With
the loss of predation and improved natality rates, some harvest is not
only a good thing, it's required to maintain maximum yield from a
watershed.

Tim

On Nov 9, 3:37 pm, Willi wrote:
[snip]
Personally, what I have trouble with are regulations and policies that
ignore the biology of the fishery in favor of "politics".
[snip]

And in that we find immutable common ground on this subject.

Your pal,

Tim

On Fri, 09 Nov 2007 22:46:09 -0000, Halfordian Golfer
wrote:

On Nov 9, 3:22 pm, daytripper wrote:
[snip]
o there is nothing obvious about a slot limit that would reduce the overall,
seasonal mortality rate. indeed, the opposite is *far* more likely: each fish
legally taken has a 0% probability of survival, while each fish released has
at least a 97% probability of survival...

You know better, we've been all over this.

I agree we've been all over this. I disagree with your conclusions, however,
as they are invariably unsupported by studies or common sense.

For one thing, if you had to kill a legal fish, in a slot, and quit, there'd be a lot less
angler pressure.

That does not describe a "slot limit", and you know it. That describes
something quite different - and you know that, too.

The quality of the experience would at once improve.

Can you support that conclusion in any fashion, short of simply repeating it?

What I suspect you really mean is, if the tourists were not to fish waters
that you'd like to fish, *you* would have a higher quality experience.

Further, the fish that remained in the system would have less
competition and watershed biomass production would be optimal.

Once again, you are stating broad conclusions that you cannot support.
Do you believe the Yellowstone River is overpopulated with trout, now?

It's also not stated, but somehow implied, that trending as close to 0
angler induced mortality through angling is even a good thing.

Regulations, for better or worse, are not based on your particular morality.

Take a poll and let us know what the preponderance of opinion is on that
particular question. My bet is nearly 100% of people would agree close to 0
angler induced mortality is a good thing.

With the loss of predation and improved natality rates, some harvest is not
only a good thing, it's required to maintain maximum yield from a
watershed.

"Loss of predation"? Where'd that come from?

Again, your conclusion could only be even remotely supportable if there was an
extant imbalance - an "over-population" of fish - in the system. If you can
provide even a single study that supports the notion that there are too many
trout in the Yellowstone, I'd be happy to review it...

Cheers

/daytripper