C&R Data

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

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, 3:37 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