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A redd is a spawning
nest that is built by salmon and steelhead in the gravel of streams or
the shoreline of lakes. It is formed by the female using her tail to dig
in a small area of gravel in the bottom of the stream or shore. Here she
forms several depressions in the gravel forming egg pockets into which
she deposits her eggs. The size of a redd depends on the size of the fish
making the nest. In the following picture Chinook redds can be seen in
the riverbed along the curve next to the forested riparian area. They
are the light colored areas in the water. Although they are apparent in
this aerial photograph they may be hard to see on the ground. Typically
redds appear as lighter areas in the gravel since the gravel has been
cleaned by the female’s movement of the gravel during spawning activity
while the area around the redd appears darker due to the normal sediment
and other biological material that remains on the undisturbed gravel.
The following diagram identifies graphically what a typical redd looks
like in profile. The downstream flow forces water through the gravel and
across the buried eggs. This brings oxygen to the eggs and alevins while
moving waste products away from the eggs. If the gravel becomes silted
in then this process cannot occur effectively.
It can also be seen
that the eggs and alevin are found relatively close to the surface. This
places them in a situation where they can be easily dislodged from the
nest and float downstream where they are subject to predation or other
mortality. The eggs or alevins are also vulnerable to crushing from either
human or vehicular traffic. This can cause direct mortality. |
