Q.
From Patrick730: How does the physical make-up of
a stream bed affect the spawning activity of trout?
A.
Answer: You’ve asked a question that would take
many, many pages to respond to, depending upon
the detail you wanted to go into. What I will do
is list some of the important physical attributes
of streams and how they affect spawning activity.
-
Substratum particle size: For successful spawning,
trout must find places in the streambed that contain the
right sized rocks for them to build their nests. This
is usually gravel sized, although bigger fish can
obviously excavate larger materials. They need to
find a site where they can dig their nest and then,
following oviposition, bury the eggs. -
The right size gravel is also important for
providing large enough spaces for the water to
continually flow over the developing eggs. This
provides well-oxygenated water for the eggs and
also sweeps away metabolic wastes and silt particles
that could smother the eggs. -
This water flowing over and through the nest must
contain adequate oxygen for the developing embryos. -
Successfully spawning also require silt-free water
so that the egg nest will not become covered with fine
particles that will preclude the oxygen-bearing water
reaching the eggs and result in effectively smothering
the eggs. -
The right size particles and interstitial spaces is
also important because when the embryos first hatch,
they spend their early developmental period living
in these spaces while they absorb the yolk sac prior
to beginning active feeding.
I hope this helps. It is brief and I’d be willing to
lead you to more extensive reading on the subject if
you’d like.
If you have a question, please feel free to contact me.
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584
Email: streamdoctor@aol.com
The ‘Stream Doctor’ is a retired professional stream ecologist and
author, now living in the West and spending way too much time
fly-fishing. You are invited to submit questions relating to
anything stream related directly to him for use in this Q & A Feature
at streamdoctor@aol.com.
Originally published March 1st, 2004 on Fly Anglers Online by Robert Younghanz.