What is a Redd?
A redd is a spawning nest that is built by Trout 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. They are the light colored areas in the water and can be some what difficult to see. 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 sac fry 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 sac fry 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 sac fry are also vulnerable to crushing from either human traffic. This can cause direct mortality.
Understanding what Trout Spawning Redds are and what they look like on the Grey Reef section of the North Platte River, will help protect our great fishery.
For another great article on Why to leave spawning fish alone.