Page Content – Salmon

Laying and fertilizing eggs

Early in spawning, as many as 1200 eggs may be released into the nest, the number decreasing in subsequent nests. As they are released, current eddies in the depression pull most eggs downward into the nest to less turbulent water where sperm has settled and where they become lodged in the gravel.

Female covering eggs

As soon as the female has released her eggs, she instinctively covers them by moving upstream slightly and repeating her digging motions. This lifts gravel just above the nest, so that the current carries it into the depression. These “covering digs” increase in intensity until the nest has been filled. Often the males will leave the female, in search of another that is preparing a nest. The female moves upstream slightly and begins digging a new nest. Spawning can last for several days. Once the females have deposited their eggs, they defend their redds until they die, about a week later. Males remain sexually active longer, roaming the stream in search of late females.

Gradually, the scene turns from a frenzied expression of life to a pathetic scene of death. Carcasses beach on the gravel, line the bottom, float downstream, and hang up in roots and limbs. Survivors swim listlessly, often drifting with the current. The scavengers arrive – ravens, crows, eagles, gulls, bears, and others. Footprints appear in the river sand overnight. The smell of rotting flesh rises out of logjams.

As the drama of spawning quiets with the death of the adult fish, the patient observer of salmon can take heart in what the process has yielded. The littered bodies, dragged into the shrubs and partly eaten, feed the entire forest. And underneath those fresh mounds of gravel on the stream bottom, thousands of eggs are already growing. The salmon are very much alive.

From the “Adopt-A-Stream Foundation Field Guide to the Pacific Salmon,” by Robert Steelquist. We are grateful to Sasquatch Books for granting us permission to reproduce this description of salmon spawning.

Female Building a Redd

Each species of salmon shows different preferences in terms of optimum spawning habitat. This ensures that available habitat is used efficiently with a minimum of competition.

The redd is the general location selected by a female for laying eggs. Within that site, she may dig several nests and deposit eggs in them over a period of several days. The female begins by “nosing,” an act in which she tests the gravel by probing, while cruising slowly over the bottom in the redd area. Having identified a suitable site, she turns on her side and begins flexing her body violently, slapping the gravel with her tail. This process dislodges gravel, which is lifted and carried slightly downstream by the current. After a series of digging motions, she swims to repeat the process. Sometimes the movements include tight circling or swimming over the nest in figure eights. Eventually, this produces a cone-shaped hollow varying in depth from just a few to as much as 15 inches (38 cm), depending on gravel composition and fish species.

The act of digging attracts males, who compete for the privilege of courtship. As a male manages to successfully ward off competitors, he joins the female in the nest in a series of movements that lead to egg and sperm release. The first of these movements is a “quiver,” in which the male moves alongside the female and his body undulates slightly. He may follow this by “crossing over” the female near the base of her tail. As the nest develops, the female begins “probing” the gravel with her tail. Gradually, the probing increases and the circling decreases. The female settles lower in the nest for longer periods. As this occurs, the male continues to quiver and frequently opens his mouth in a “gape.”

As the female nears egg deposition, she begins to “crouch,” a position much like the probe, but with mouth agape. By opening her mouth, she increases her resistance to the current, which forces her deeper into the nest cavity. When the female assumes the crouch, the male quickly moves alongside. Both rapidly vibrate their tails and the eggs and sperm are released. The eggs emerge from the female one or two at a time into water clouded by the sperm, or milt. As this occurs, other males stationed outside of the nest may rush in to try to fertilize the eggs themselves. If the dominant male makes chase, another male may try to occupy the nest.

From the “Adopt-A-Stream Foundation Field Guide to the Pacific Salmon,” by Robert Steelquist. We are grateful to Sasquatch Books for granting us permission to reproduce this description of salmon spawning.

Spawning Sockeye Salmon

Salmon spawning is a remarkable phenomenon to behold. Generally, spawning is broken into three types of behavior: redd selection and nest building, courtship and mating, and nest closure. Although individual species differ in certain behaviors, a generalized pattern occurs with all salmon.

Redd selection is the task of the female and is based on a variety of factors. Stream velocity, water depth, and gravel size determine the general suitability of a given site. The ability to claim and defend a redd site and the actual physical strength to excavate the nests vary with each fish.

From the “Adopt-A-Stream Foundation Field Guide to the Pacific Salmon,” by Robert Steelquist. We are grateful to Sasquatch Books for granting us permission to reproduce this description of salmon spawning.