TR Cascade River

Jonathan Cook wrote:

Willi wrote in message ...

Higher water temps are generally the limiting factor in where trout can
survive. As a river flows downstream, average temps generally rise until
they reach the point where the trout can't survive.


Willi, have you ever explored downstream to see if trout move down at
different seasons? I could imagine that trout move down in winter (if
there's enough water) and maybe back again when it gets too warm. You've
talked here before about daily migrations of a hundred yards, but are
there seasonal migrations on the order of miles?

I've never read anything about that except for some reports from the
East where the trout will migrate in the Summer to spring heads to get
relief from the rising temps. I don't know how far they go.

From what I've read, in some Yellowstone rivers, the trout migrate in
and out of certain areas.

Locally what I've observed is that they "hole up" during either high or
low temps. During these low flow periods, I can clearly see the bottom
of all but the very deepest pools and not see a fish. An influx of water
or a moderation in temps will bring them out.



I could also imagine that in high-runoff years, quite a few trout may
find themselves (either "purposefully" in their pea-brains or accidentally)
quite a ways downstream, and not really make an effort to move back up
as the water warms. This could be an opportunity to harvest some decent
trout that would otherwise perish anyways. Maybe in the few weeks after
runoff and before the water really starts warming up.


I think that since they evolved with runoff, they've adapted well to it.
I'm sure there's some fish that end up like you describe. One of the
things they do locally is run up irrigation canals during runoff, but
when the water recedes some of them will get stuck. A few of them find
spots that consistently hold enough water so they can live there. In the
irrigation canal that borders my property, there's a big brown that
lives under the bridge that's been there several years, even though
flows in the Summer can be almost like bathwater.



I guess it should be noted that you live near streams that make a
fairly abrupt change from good trout water to uninhabitable, with
a fairly short amount of "marginal" habitat. In other areas of the
country, this situation may be uncommon (I'm guessing).


I think many streams and rivers share this at some point. They flow from
elevation which keeps them cool enough to support trout, but as they
descend they reach an area where the water becomes too warm to support
them.

Willi

Willi,

In another post in this thread, I referred to a radio tracking study of
brown trout on a local stream which showed that trout lose considerable
weight over the winter, (at least in the experiment). I do not have a
report, only recollection of a preliminary verbal presentation of findings.
Among the discoveries was that trout do move around, some moving
considerable distances, 8-10 kms, others not as much.

Radio tracking is glamorous and consequently is somewhat of a fad among
field biologists working on almost every species imaginable these days. Some
aspects of it on some species bothers me. For instance, I was disturbed by
tracking experiments on endangered sea turtles; even to my untrained eye the
particular transmitter used had to have affected the hydrodynamics of the
creature. Most researchers never recover their specimens but I recall
reading of one team that did and found their specimen wasted and about to
die, presumably because of an inability to swim normally and feed. The lead
scientist chose to end his program at that point because of that. In the
case of trout in my home river, there was a very high mortality of the
specimens for reasons that apparently could not be identified. My suspicion
is that the fish might have been very highly stressed not by the transmitter
itself but by the procedure to install it. The fish are out of the water
for 5-10 minutes during which time they are only doused with water laced
with a disinfectant. This is inconsistent with the preachings of other
biologists who advise anglers to release their catch as quickly as
possible - I am surprised that any survived at all. However, in the case of
fairly abundant species such as trout, I suppose sacrificing a few to find
information to save many is a worthwhile trade off.

Yuji Sakuma

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"Willi" wrote in message
...


Jonathan Cook wrote:

Willi wrote in message
...

"Yuji Sakuma" wrote:

I have three experiences with this sort of stuff.

Several years ago I talked to a biologist at the Tokul Creek steelhead
hatchery in Washington. He said that some times the fish return early
to the hatchery and they keep them in concrete pens until they ripen.
In one cast this was 4 months with no attempt to feed the fish. He
said the fish lost some weight, but the eggs developed normally and the
fish were released after the eggs were stripped from them. These were
7-10 pound fish that survived not eating for 4 months.

Another item was what we saw last summer on Rock Creek. The water was
too warm in the lower creek, so the fish migrated up to the upper
sections. This was easily a 10 to even 20 mile migration, and I think
that's common for Rainbows and Cutthroats.

I caught a Steelhead in the upper Cedar hears ago that had been tagged
3 days earlier at the Ballard locks. That's probably 20 to 30 liles of
swimming through t lakes and a river. The fish fought hard and tasted
fine.

Chas
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