Day 2: Salmon Spawning: A simple yet complex ocean-forest relationship

Question of the Day:

Why is the health of the marine ecosystem important to humans?

Character of the Day:

Spawning Migration: It is unsure as to how exactly salmon detect their birth streams, though it is suspected that scents and chemical cues, as well as the sun, play an important role in the homeward migration. Once the salmon reach the freshwater of the stream, they stop feeding. During the course of the journey, their bodies instinctively prepare for spawning. The taxing journey draws energy from their fat storage, muscles, and organs, except for the reproductive organs. Males develop hooked noses, or kype, in order to fight for dominance.

Key Concepts:

How do salmon benefit forests?

The relationship between salmon and trees is more significant than you would think along the Lost Coast. Salmon and forest actually need each other. Salmon that die in the streams become part of the forest ecosystem by fertilizing riverside vegetation; and the woody debris that falls from the forest into the streams improves salmon breeding success of salmon.

Studies of pacific salmon in rivers along the Northern Pacific Ocean show that migrating salmon are a conveyor belt of nutrients for the ecosystem. Pacific salmon move nitrogen and phosphorus upstream from the Pacific Ocean to the interior stream habitats. Here the fish spawn, die, and are decomposed by bacteria and fungi. Young fish travel downstream, grow in the sea, and repeat the process when they are mature enough to reproduce. Trees on the banks of salmon-stocked rivers grow more than three times faster than their counterparts alongside salmon-free rivers. In fact, the certain species of spruce trees have been found to only take 86 years, rather than their usual 300 years, to reach 50 centimeters thick. Some researchers suggest that years of good or poor growth among these trees can be related to the success of salmon populations during those years (related to the width of the individual tree rings).

Salmon, in turn, need big trees. They clean and shade the water, helping eggs and young salmon to survive. Strong currents cannot shift their heavy debris, leaving small fish somewhere to hide.

Bears along the Lost Coast love salmon, during peak periods when salmon are spawning bears carry hundreds of kilograms of fish out of streams and into the forest to consume. With the abundance of fish, the bears can afford to selectively gorge on their favourite parts of the fish, the eggs (or roe), brain, skin and back muscles, before they move on to the next fish. Sometimes they eat as little as five percent of the fish, leaving the rest to decompose on the forest floor. That is where the relationship between the bears and the fish connects to the trees.

Tree growth in coastal forest ecosystems is often limited by the availability of the element nitrogen. Gardeners can tell you that fish fertilizer is a potent and effective way to increase the health and size of your garden plants, and the same goes for these trees. The fish left behind by the bears are packed with nitrogen, which fertilizes the trees (and other plants) and helps them grow to their impressive size. It sounds simple, yet the science behind it is almost as fascinating as the process itself.

This relationship also suggests that forest and salmon management should be integrated. Accordingly, other threats to salmon populations, such as pollution or overfishing, may affect forest ecosystems. Salmon populations are declining along the Pacific Ocean. In the past century salmon numbers in California, Oregon and Washington, for example, have fallen by about 90 percent. The geographical scale of the trends has led researchers to assume that the cause lies in the ocean itself, and is perhaps related to climate change. Riverside vegetation gets just under a quarter of its nitrogen - the nutrient that most commonly limits plant growth - from salmon.

Youth Ambassador Activity:

Maybe have YA march from stream-side (assuming we know it is a salmon spawning region), measuring tree diameters as they move from the edge of the stream to illustrate tree size dependency on salmon carcass fertilizer.

School Activity:

This lesson plan can be adapted for students in grades 10-12. Students work in small groups to create solutions to a long-standing problem by designing and drawing a dam appropriate for the survival of salmon.


Students have a chance in this activity to create solutions to a long-standing salmon problem: Dams. Idaho is losing its salmon population because the fish migration is blocked by eight dams on the Snake and Columbia Rivers. Biologists and engineers have tried a number of ways to help the salmon move through and around the dams, and for a while some of these methods seemed to work.

Unfortunately, salmon numbers continue to decline — a sure sign that the methods are not working and something new must be tried. Some people have proposed removing four of the dams. Even if this occurs, four more will remain. So we will still need new ideas to help the salmon around these dams. Who better to begin the work than tomorrow's biologists and engineers?


For each group of students:


The student will be able to:

  1. Identify problems experienced by salmon in migration.
  2. Identify mitigations that have worked and those that have not.
  3. Share conclusions and evaluate other group conclusions and project designs.


  1. Write the following topics on a board, large sheet of paper, or overhead transparency:
  2. Divide students into small groups of three or four students; instruct the groups to decide which group will research which topic. To cover all topics, groups may need to choose more than one.
  3. Allow sufficient time for the groups to conduct their research and to present their information.
  4. Re-assign the students into new small groups so that each group contains an "expert" on each topic above. Instruct these new groups to design a dam that will produce electricity efficiently or store irrigation water, and provide safe passage for salmon.

Daily Dispatch

What would awaking in a place where there is no memory of, be like? Emerging from below ground and water, in a bed of pebble rock, I wiggled out of my tiny protective cocoon. I knew not where to go, but I knew I needed to move. But how do I move. Somehow I knew to kick, so I kicked. Unlike a human emerging from the womb into the comforting embrace of its parents, I emerged into new land, and while I do not know for sure if it was a hostile environment, this would certainly felt like it was one. In a blinding flash of brightness that didn’t shut off, I emerged in a never-ending sensation of pressure. I gasped for life as I pitched to and fro. With many passages of light and dark, I was able to sense my new surroundings. At times I was pushed into less hostile regions, and there I was able to take refuge in the near darkness. I did not know why, but I was drawn time and again back into that hostile environment, thinking there could be nothing worse, but then it came. I hit a wall, an impregnable wall that made my body hurt. It was a wall that felt like I should not and could and should not pass over. But with many more passages, I could see the top of the wall, and then in one period of brightness, over it. There it was dark, and I could not see boundaries. Should I turn around and go back? I do not know why, but I began sense a need to climb the wall. Was there something calling me? Will there be others like me? With the other side of the wall be more dangerous to me? How will I get back?