Halfordian Golfer wrote:


Hi Willi,

I haven't seen any of the study URL's that I'd asked about to help
clarify your question, which, I'm sorry but is not specific enough to
be useful.

Here is a specific study on optimal partial harvesting:
http://tiny.cc/2g3hKhttp://tiny.cc/2g3hK (download the pdf).

Abstract When growth is density dependent, partial harvest of the
standing
stock of cultured species (fish or shrimp) over the course of the
growing season
(i.e., partial harvesting) would decrease competition and thereby
increase indi-
vidual growth rates and total yield.

Now, this is the basic fisheries management theory. Not 'exactly' what
you asked but it demonstrates the concepts clearly.



Your URL didn't work for me. However, from abstract, it was based on
cultured, not wild populations.

Like I tried to explain to you, I have no trouble with you
philosophical/religious position on C&R fishing. Like religion, that's a
personal choice based on an individual's own values.

However, I do object to, what I see as, your pseudo biological
explanations for
C&R which is why I changed the subject to fishery management. I was hoping
that you could discuss this in a more "scientific" vein. This is an area
that interests me and I've done considerable reading on it. You make
statements about how a C&R or any fishery can be "improved" by harvest.
There
are many studies done on the effects of different of regulations on fish
populations,
but I've NEVER seen a study based on a self sustaining trout population
that
shows what you claim. I asked you to cite one study.

Below are three examples of statements you have made concerning harvest
"improving" a fishery:

" Willi you just said that reducing harvest can improve a fishery. So
can increasing harvest. This is as old as the hills. Don't make me
spell out "S-T-U-N-T-E-D" again. There is no question about it.

I am interested in culling the fish that makes the
most sense for the given situation and large fish are good candidates
because they start to create negative yield from a fishery. Slots on
both sides with restricted bags and restricted fishing, instead of C&R
and watch the quality of the fishery soar.

It is undeniable and unequivocal. Partial Harvest increases individual
growth rate and total yield, at the very least in some situations, of
recruitment, available forage, size and nature of habitat, etc."


I asked (and still ask) you to show me ONE study done with a self
sustaining
population of trout in a stream or river that the supports any one of
the above
statements you made. There are tons of studies showing that reducing
harvest improves a fishery
in this manner. If you like I'd be glad to cite some (in addition to the
one YOU cited). I also cited two studies (and there are more) that showed
that "culling" large fish leads to a decrease in size of the
populations, which I felt you
discounted because it didn't agree with your position.


When I asked this in a past post, the study YOU cited was:

http://www.wnrmag.com/stories/2007/oct07/fishery.htm

The study didn't show that harvest improved the fishery rather that
REDUCING the harvest increased the number of "catchable" and large
trout as well as increasing the total trout biomass in a stream.

I'll try again.

1. Show me ONE study where a self sustaining stream based trout fishery
with C&R regulations was "improved" (use the article YOU cited as an
example of "improved") when harvesting was again allowed.

or

2. Show me ONE study where a self sustaining stream based trout fishery was
"improved" when harvesting was increased.

If you answer this post, please address question 1 and 2. "Improved"
needs to be
based on fish population statistics, not aesthetic opinions.


Willi