Sockeye salmon and Kokanee salmon
Sockeye salmon and Kokanee salmon are two closely related species of fish belonging to the same family, Salmonidae, but they have distinct lifestyles and habitats. Sockeye salmon, also known as Oncorhynchus nerka, are anadromous fish, meaning they hatch in freshwater, migrate to the ocean to mature, and return to freshwater to spawn. They are known for their striking transformation during spawning, changing from a dull coloration to a vibrant reddish-orange, particularly in males. Sockeye salmon can reach lengths of 1.5 to 2.5 feet and weigh between 5 to 7 pounds, though larger individuals have been recorded.
In contrast, Kokanee salmon are the landlocked, non-migratory form of sockeye salmon that live in freshwater lakes. They typically resemble trout but are distinguished by specific fin structures and lack of distinct dark spots. Kokanee can vary greatly in size, reaching lengths from 4 to 24 inches, depending on their food availability. Both species are semelparous, meaning they die after spawning, with lifespans generally ranging from four to five years, though some may live up to eight years. Their diets overlap to some extent, with sockeye primarily consuming oceanic prey such as zooplankton, while Kokanee feed on insects and snails in their freshwater environments. Both species face predation from various wildlife, including birds and larger fish.
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Sockeye salmon and Kokanee salmon
The sockeye salmon is one of the most valuable Pacific salmon on the commercial market. It is known for its oily flesh and great flavor. When the sockeye salmon leaves the ocean for its spawning run upriver, its dull coloring changes to a deep reddish orange.
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Oncorhynchus
Species: Nerka
Sockeye salmon are anadromous fish, meaning they hatch and rear, up to the smolt stage, in freshwater and then migrate to salt water oceans to mature. They then return to freshwater to spawn and eventually die. Sockeye salmon can be found throughout the Pacific Northwest, from northwest Alaska south to the Deschutes River in Oregon.
The adult sockeye salmon reaches a length of 1 1/2 to 2 1/2 feet (46 to 76 centimeters) long and a weight of five to seven pounds (two to three kilograms). However, they can grow even larger, and some sockeye salmon have been caught at a weight of 15 pounds (seven kilograms). Present inside the fish are a small number of gillrakers, and on its back is a series of tiny spots. Their color changes over the course of their life. After sockeye salmon hatch, they lack pigmentation. As they mature, they become green with spots and eventually blue. When the male sockeye is of reproductive age, they turn their distinct bright red shade. The female's body becomes dark olive to light red. She is darker on the sides than the male.
The diet of sockeye salmon consists of euphausiids, zooplankton, and other small crustaceans.
From March to July, sockeye salmon inhabit rivers, particularly those which branch from lakes. Some spawn in streams which are not fed by lakes. Spawning takes place when a female fish deposits her eggs in nests she digs, or redds, for the male to fertilize. She can deposit anywhere from 2,000 to 4,500 eggs. Typically, though, only a portion of the eggs layed make it to the hatching stage. Spawning in lakes takes place between August and December. Sockeye salmon first spawn when they are four to six years old, but some are as old as eight years before they first spawn. Sockeye salmon are semelparous, meaning they die after spawning.
After hatching, sockeye salmon remain in the lakes for one to three years. Then, from March to May, the young, called fry, migrate to the ocean. Some sockeye salmon do not migrate to the ocean. These fish are known as kokanee, and they are the landlocked, non-anadromousor non-migratingform of sockeye salmon. Aside from their inability to migrate and some slight differences, particularly in environment and appearance, Kokanee are the same taxonomy and species as sockeye salmon. Kokanee salmon can be found in fresh lakes throughout the United States where they have been stocked. They can also be found in lakes throughout Asia and Canada.
Kokanee look like trout. They differ from trout in that their anal fins have more than 12 rays. Each ray has a thin spine connected to the ray by a web-like material. They also lack the distinct dark spots on their back and fins that many trout and other salmon have.
The length of kokanee varies greatly. They can reach full-grown lengths of 4 to 24 inches (10 to 60 centimeters). How large a particular kokanee becomes depends on how easily it can find food. Kokanee are considered to be adults at a length of eight to nine inches (20 to 22 centimeters).
An example of how kokanee grow can be seen by studying those of Idaho's Lake Pend Oreille. Studies of the lake's kokanee population show that the fish reach a length of two to three inches (five to eight centimeters) in their first year, seven to eight inches (18 to 20 centimeters) in their second year, eight to nine inches (20 to 23 centimeters) in their third year, and 10 to 12 inches (25 to 30 centimeters) in their fourth year. Kokanee do most of their growing from July to October with very little growth taking place in the winter.
The kokanee salmon's diet is somewhat different than the sockeye salmon's diet because they do not inhabit the ocean. Kokanee salmon typically feed on insects and snails, and they, like sockeye salmon, also consume zooplankton. Like sockeye salmon, kokanee salmon are semelparous and die after spawning. Their lifespan, and the lifespan of sockeye salmon, is typically four to five years, though the oldest salmon caught on-record was eight years old.
Both sockeye salmon and kokanee salmon are preyed upon by a variety of creatures, including humans. Bears, eagles and other large birds, and large fish eat salmon, though most predation occurs in freshwater environments.
Bibliography
Dueck, Kathryn. “Kokanee Salmon.” A-Z Animals, 13 Dec. 2022, a-z-animals.com/animals/kokanee-salmon/. Accessed 4 May 2024.
Fisheries, NOAA. “Sockeye Salmon.” NOAA, 22 Dec. 2023, www.fisheries.noaa.gov/species/sockeye-salmon. Accessed 4 May 2024.
Kennedy, Stephan. “Oncorhynchus Nerka (Kickininee).” Animal Diversity Web, animaldiversity.org/accounts/Oncorhynchus‗nerka/. Accessed 4 May 2024.
“Sockeye Salmon.” Alaska Department of Fish and Game, The Great State of Alaska, www.adfg.alaska.gov/index.cfm?adfg=sockeyesalmon.main. Accessed 4 May 2024.