Salmon are an iconic group of fish, recognized globally for their remarkable life cycles and their significance in both natural ecosystems and human diets. They are found across the Northern Hemisphere, inhabiting both freshwater and marine environments. Salmon possess a sleek, torpedo-like body, typically with silvery scales that can change coloration during different life stages. They are classified within the family Salmonidae, which also includes trout and char.
Pacific Salmon Species
The Pacific Ocean is home to five species of salmon, all belonging to the genus Oncorhynchus. These species are anadromous, meaning they hatch in freshwater, migrate to the ocean to grow, and then return to their natal freshwater streams to reproduce.
Chinook salmon (Oncorhynchus tshawytscha), also known as King salmon, are the largest of the Pacific species, with some individuals exceeding 100 pounds. Their bodies are typically blue-green on the back with silvery sides and black spots on their backs and both lobes of their tail fin. A distinguishing feature is their black gumline. Chinook salmon inhabit rivers from California to Alaska and across to Asia, often undertaking extensive migrations.
Sockeye salmon (Oncorhynchus nerka), often called Red salmon, are known for their vibrant red bodies and green heads during spawning. In the ocean, they have iridescent silver flanks and a metallic green-blue top, generally lacking large spots. Sockeye typically range from 1.5 to 2.5 feet in length and weigh between 4 and 15 pounds. They are commonly found in the Northern Pacific Ocean, from the Columbia River north to the Canadian Arctic and west to Japan and Siberia, preferring lake-fed systems for spawning.
Coho salmon (Oncorhynchus kisutch), also known as Silver salmon, average 24 inches long and 8 to 9 pounds, though some can reach up to 20 pounds. They possess dark metallic blue or greenish backs with silver sides and small black spots on their backs and the upper lobe of their tail fin. Unlike Chinook, coho have white gums. Coho salmon are widely distributed along the Pacific coast, from California to Alaska and across to Russia and Japan.
Pink salmon (Oncorhynchus gorbuscha), or Humpback salmon, are the smallest and most abundant Pacific species, typically weighing 3.5 to 4 pounds. They have a steel-blue to blue-green back and silvery sides in the ocean, with large oval spots on their back and tail. Spawning males develop a distinct hump on their back. Pink salmon have a two-year life cycle and are found across the Pacific Rim, often spawning close to river mouths.
Chum salmon (Oncorhynchus keta), also referred to as Dog salmon or Keta salmon, typically weigh 6 to 15 pounds and can reach up to 3.6 feet in length. In freshwater, they develop distinctive bold red and black tiger stripes, and males grow large, canine-like teeth. Chum salmon are found throughout the Pacific Rim, from Oregon to Alaska and extending to Japan and Korea. They exhibit a hardy nature and can spawn in both saltwater and freshwater environments.
Atlantic Salmon
The Atlantic Ocean is home to a single species of salmon, Salmo salar, known simply as Atlantic salmon. Atlantic salmon are also anadromous, starting their lives in freshwater rivers before migrating to the ocean.
Atlantic salmon typically measure around 28 to 30 inches and weigh 8 to 12 pounds, but can grow much larger. In the sea, they are silvery with a blue-green back and small black spots, mainly above the lateral line. Upon returning to freshwater for spawning, their coloration darkens, often becoming mottled brown, with spots becoming more pronounced. Atlantic salmon are distributed across the North Atlantic, from North America (Quebec to Long Island) to Europe (Norway, Iceland, UK, Ireland) and the Baltic Sea. Historically abundant, wild populations in some regions, like the United States, are now limited to a few rivers in Maine due to factors such as habitat degradation and overfishing.
Key Distinctions Among Salmon Types
Understanding the differences between Pacific and Atlantic salmon, and among Pacific species, involves examining their life cycles, physical appearance, and geographic distributions.
Spawning
A primary difference lies in their spawning behavior. Pacific salmon species are semelparous, meaning they reproduce only once in their lifetime and typically die shortly after spawning. Atlantic salmon, conversely, are iteroparous; they can survive spawning and return to the ocean to reproduce in subsequent years, although not all individuals do so.
Appearance
Atlantic salmon can be identified by having fewer than 13 rays in their anal fin, a feature that distinguishes them from Pacific salmon which typically have 13 to 19 rays.
Geography
Geographically, Pacific salmon species are native to the North Pacific Ocean and its tributary rivers, spanning from California to the Arctic and across to Asia. Atlantic salmon are found exclusively in the North Atlantic Ocean basin, including rivers flowing into it from North America and Europe. This clear oceanic separation helps in broadly categorizing salmon types.