Salmon are a diverse group of fish known for their remarkable life cycles and distinct characteristics. These migratory fish undertake journeys between freshwater and saltwater environments, contributing to aquatic ecosystems and human economies. This article explores the different kinds of salmon and how to distinguish them based on their physical attributes and life cycles.
Major Salmon Groups
Salmon are broadly categorized into two main groups: Pacific salmon (Oncorhynchus) and Atlantic salmon (Salmo). This classification reflects fundamental biological differences. The Pacific group encompasses several distinct species found in the Pacific Ocean and its tributary rivers. Atlantic salmon are native to the Atlantic Ocean and the rivers flowing into it.
Pacific Salmon Varieties
The Pacific salmon group includes five primary species found in North American waters: Chinook, Coho, Sockeye, Pink, and Chum. Each species exhibits unique traits in appearance, size, and life history. Pacific salmon are anadromous, hatching in freshwater, migrating to the ocean to mature, and returning to their natal freshwater streams to spawn. A defining characteristic of all Pacific salmon is their semelparous reproductive strategy, where individuals spawn once and then die.
Chinook salmon, also known as King salmon, are the largest Pacific species, often reaching three feet and 30 pounds, though some can exceed five feet and 100 pounds. They are blue-green on their back with silvery sides, irregular black spots on their back, dorsal fin, and tail fin lobes, and a black gum line. Coho salmon, or Silver salmon, are smaller, averaging 24-30 inches and 8-12 pounds. They have bright silver sides, small black spots primarily on their back and upper tail fin lobe, and white gums. During spawning, their sides turn maroon to reddish.
Sockeye salmon, often called Red or Blueback salmon, are vibrant red with green heads during spawning, but iridescent silver with a metallic green-blue top in the ocean. They are smaller, 18-31 inches long and 4-15 pounds, and lack large spots on their back or fins.
Pink salmon, or Humpback salmon, are the smallest Pacific species, 20-25 inches long and 3.5-5 pounds. They are identifiable by large dark oval spots on their back and entire tail fin, and spawning males develop a distinct hump. Chum salmon, also known as Dog salmon, are robust, second in size only to Chinook, averaging 24-40 inches and 8-15 pounds. In freshwater, they develop striking red and black tiger stripes, and males grow large canine-like teeth.
Atlantic Salmon Variety
In contrast to Pacific salmon, there is only one species of Atlantic salmon, Salmo salar. This species is native to the northern Atlantic Ocean and its tributary rivers, including those in North America and Europe. Adult Atlantic salmon typically measure 28-30 inches and weigh 8-12 pounds after two years at sea, though some can grow larger. They are characterized by a steel-blue or silver coloration with black spots predominantly above the lateral line, and their caudal fin is usually unspotted.
A key biological distinction for Atlantic salmon is their iteroparous reproductive strategy. Unlike Pacific salmon, Atlantic salmon can survive spawning and return to the sea to spawn again. While most individuals spawn once, some can be repeat spawners. They recondition in the ocean between spawning events to regain energy.
Key Differences Among Salmon
Distinguishing between salmon types involves considering their life cycle, appearance, geographic range, and size. A fundamental difference is their reproductive strategy: Pacific salmon spawn once and die, while Atlantic salmon can spawn multiple times.
Geographically, Pacific salmon species are found along the Pacific Rim, from California to Alaska and across to Asia. Atlantic salmon are restricted to the North Atlantic Ocean basin. While both groups are anadromous, their physical appearance varies, particularly during spawning. Pacific salmon undergo dramatic color changes, developing humps or hooked jaws, and exhibit distinct spotting patterns. Atlantic salmon, while changing color during spawning, do not develop the pronounced humps or jaw deformities seen in many Pacific species, and their spots are typically limited to above the lateral line.
In terms of size, Chinook salmon are generally the largest overall. Atlantic salmon can also reach considerable sizes, often exceeding most individual Pacific salmon species other than Chinook. Pink salmon are consistently the smallest of all salmon types. These variations in size, coloration, and life history provide cues for identifying the different kinds of salmon.