In this unit we will be diving further into the inner workings of Pacific Salmon, and looking at their broader role in the ecosystem. This module is designed for students in grades 3-6, or anyone with a basic knowledge of salmon. It is recommended that participants have completed our Primary Module, or have looked it over as a refresher prior to taking this course! We will be looking at habitat requirements in both fresh and saltwater, as well as challenges faced by Pacific Salmon.
We will ask those same questions and a few more at the end of this lesson so you can show off how much you have learnt!
Our main focus for this unit will be - salmon life stages, the types of Pacific Salmon and details about their life cylces.
Salmon Life Stages
Pacific Salmon have a very distinct lifecycle, that is very unique as it includes both a freshwater and saltwater component. This begins as adult salmon return to the stream they were born in (their natal stream) every year from August until November.
A female salmon that has entered a river or stream to spawn will begin looking for a suitable area to lay her eggs. This area will usually have small stones that the salmon can dig out into a nest, known as a redd. The female will choose a male, who will fertilize the eggs simultaneously to them being laid by the female. Often times, smaller jack salmon will sneak in and fertilize a portion of the eggs as well, increasing genetic diversity. After the eggs have been laid and fertilized, they will be covered by the female salmon. All of the above can be seen in the video below!
Once the egg has been fertilized, it will start growing immediately. Egg development depends greatly on water temperature. Usually it will take between 20 and 35 days for eggs to start showing eyes.
Above you can see the fully developed eyes in a group of Chinook eggs that are close to hatching out. These fish will hatch out between 45-65 days after they have been fertilized into what are called Alevin
Alevin are the first stage we start to see the fish shape emerge. These young salmon are still reliant on there yolk sacks for nutrients, and will remain in the gravel for a few weeks after they have hatched.
As they absorb and digest more of their egg sack, they will begin growing. Near the end of this life stage, they will slowly begin feeding on microscopic zooplankton, doing so until they have closed over their egg sacks and begin to swim freely as
The salmon fry stage is when more noticable differences between the species of salmon start to emerge. Not only do more distinct physical characteristics start showing, but life cycle differences begin to become apparent. Salmon fry are free swimming, and can be seen feeding in slower sections of creeks and rivers.
This is a period of slow growth as the young salmon adjust to their surroundings, and because they are living in cooler spring water temperatures. They will develop parr marks as they grow, which they will lose when they gradually turn into smolts. Chinook, Chum, and Pink Salmon fry will all move into the saltwater environment fairly quickly in the spring, where as Coho and Sockeye will spend a year in fresh water lakes and streams prior to migration.
As a salmon fry begins to prepare for its journey to the ocean, it goes through a process called smolting. The small salmon will lose it's parr marks, and prepare for the change from freshwater to saltwater.
Once the smolt has reached the ocean, it will start growing at a very fast rate, and will spend 2-5 years feeding and growing. Below is a great video by Ocean Wise on the journey of an Adam's River Sockeye!
Species of Pacific Salmon