Some C&R Information

Scott Seidman wrote:


Boy, I'd love to see the original paper. Just to lend a scientists eye
to this paragraph, I've seen the techniques used by the NYS DEC, and
frankly question such an organization's ability to quantify the fish
population to within 20%. You'd have a hard time convincing me that
Montana can do much better. When I see a 20% difference in this context,
my thought process brings me to "about the same". Could be that the data
collectors just had a better day of shocking in their control region.

Next, you'd have to show me some convincing data that fish populations in
the C and R area were EVER the same as in the closed section, given the
same techniques for population assessment. How far apart are they? Is
the forage base the same? Water chemistry? Bank and bed conditions?
Bird predation? Pollution?

Now, having demonstrated that a) the population difference is real, and
b) the population difference (if any) is not a natural manifestation of
the habitat (i.e., that their "control" no-fishing region is a valid
comparison), you've still got a long way to go to establish that the
difference is due to release mortality. At the very least, you'd have to
provide me with a good harvest estimate, a good population estimate, a
ballpark release mortality estimate, and then show me that the numbers
would add up to a 20% population hit.

Not that I have any problem believing that C and R fishing access can
cause a 20% population hit, I just have a hard time believing that a DNR
can prove it.


I was interested too, but I wasn't able to find the original paper. I'll
look some more when I have time. You make some good points, but in a
natural system like a river, it is extremely difficult/impossible to
control all the variables. The results you get are from a survey, not an
experiment.

A couple things:

The two sections of river are contiguous sections of the Madison and
they are VERY similar (part of the "fifty mile riffle"). I'm "sure" they
measured fish populations in both pre and post. There was no legal
harvest on either section. Before the study, they both had the same
regulations.

Montana has the most professional state fish and game department that
I'm aware of. During one of the Claves we ran into State workers doing
fish counts and measurements. They actually try and manage their
fisheries based on SCIENCE. I wish Colorado even approached their
philosophy. They're the State that showed that the introduction of
catchable trout into a system that has a self sustaining trout
population, actually reduces the trout holding capacity of the system.
They followed that up by stopping the stocking of catchable in most? of
their streams and rivers, although, at the time, I'm sure it was a very
unpopular decision. That study is on the internet and I'm guessed that
the methodology is similar.

You're right the study isn't perfect but it's the best that we have for
measuring C&R mortality over time. IMO, it is MUCH better than the C&R
mortality "experiments" that have been done. I think that more
significant variables are controlled in this type of study than in the
C&R "experiments".

Willi