How Long is a Typical Salmon? Unpacking the Life Cycle of these Iconic Fish

Salmon are one of the most recognizable fish species in the world. They are known for their remarkable migrations from freshwater rivers to the ocean and back again to spawn. But just how big do salmon grow during their complex lifecycle? In this article we’ll explore the typical length of salmon at different life stages.

Salmon belong to the family Salmonidae and are split into two main groups – Pacific and Atlantic salmon There are noticeable differences in size between salmon species and populations, but some general trends emerge when looking at their growth from eggs to spawning adults

Egg Stage Length

The life of a salmon begins as a tiny egg buried in a nest of gravel on the floor of a stream or river. Salmon eggs are small, ranging from 4 to 7 millimeters in diameter – similar in size to a pea or marble. Though microscopic at this stage, the salmon embryo continues to grow and develop inside the egg casing.

Alevin Stage Length

After incubating for several weeks or months, the salmon egg hatches into an alevin. Alevins are characterized by a large yolk sac attached to their bellies which provides nourishment. At this stage, an alevin can be 20 to 25 millimeters long, not including the yolk sac. They continue to grow as they absorb the yolk, emerging from the gravel 2 to 3 months later as free-swimming fry.

Fry Stage Length

Once they absorb their yolk sac and emerge from the gravel, salmon fry are typically 25 to 40 millimeters in length. Some species, like pink and chum salmon, will migrate downstream to the ocean soon after reaching the fry stage. Others, like Chinook, coho, and sockeye salmon, may spend a year or more in freshwater as fry before undergoing the smolt transformation for ocean migration.

Smolt Stage Length

Young salmon change from living in freshwater to living in saltwater during the process of smoltification. In order to get ready for ocean migration, their bodies change, and they look more streamlined and silvery. Different types of salmon smolts are different lengths, but at this stage, most are between 10 and 15 centimeters long.

Ocean Phase Length

The ocean phase represents the period of fastest growth in a salmon’s lifecycle. With abundant food resources, salmon can grow rapidly as they mature in the sea.

• Pink and chum salmon spend only 1 to 2 years in the ocean before returning to spawn. During that time they reach lengths of about 40 to 70 centimeters.

• Sockeye salmon typically spend 1 to 4 years at sea and reach lengths of 55 to 80 centimeters

• Coho salmon also spend 1 to 4 years in the ocean, growing to 60 to 90 centimeters.

• Chinook salmon live in the ocean for the longest time, 3 to 5 years, and grow to be 70 to 110 centimeters long.

• Atlantic salmon can spend up to 4 years at sea and reach lengths over 100 centimeters.

So the time spent feeding in the rich ocean environment allows salmon to reach their full adult sizes.

Spawning Stage Length

When salmon return to freshwater rivers and streams to spawn, they undergo physical changes but no further growth.

• Spawning pink salmon average 40 to 60 centimeters in length.

• Chum salmon range from 50 to 80 centimeters when spawning.

• Sockeye salmon measure between 55 and 80 centimeters at this final stage.

• Coho salmon span 60 to 90 centimeters as spawners.

• Chinook salmon range from 70 to 110 centimeters when they return to spawn.

• Atlantic salmon can exceed 100 centimeters in length at maturity.

After spawning, the adult salmon die and the cycle begins anew. Their bodies deliver important nutrients to the ecosystem to fuel the next generation.