Salmon weight depends almost entirely on species, and the range is enormous. A mature pink salmon fresh from the ocean might weigh around 2 kg (about 4.5 pounds), while a large Chinook can exceed 20 kg (44 pounds) or more. Between those extremes sit four other commonly harvested species, each with its own typical range shaped by genetics, ocean diet, and how many years the fish spent at sea before returning to spawn.
Average Weights by Species
The Pacific salmon genus (Oncorhynchus) contains five commercially important species, and then there is Atlantic salmon (Salmo salar), which belongs to a separate genus. Here is what you can expect each species to weigh at maturity, based on typical returning adults:
- Chinook (King): The heavyweight of the salmon world, averaging roughly 10 to 15 kg (22 to 33 pounds) and frequently reaching 20 kg or more. Fish over 13.6 kg (30 pounds) are sometimes called “tyee” in sport fishing. Chinook spend up to five or six years at sea, which gives them more time to pack on mass than any other Pacific species.
- Chum (Keta or Dog): The second-largest Pacific species, typically 4.5 to 6.8 kg (10 to 15 pounds). Chum are wide-bodied fish that can occasionally reach 10 kg or more, and they are a mainstay of the commercial harvest in Alaska.
- Coho (Silver): Usually 3.5 to 5.5 kg (8 to 12 pounds). Coho spend only about 18 months in the ocean, which limits their upper size compared to Chinook and chum.
- Sockeye (Red): Typically 2.3 to 3.2 kg (5 to 7 pounds) at the time of spawning. One large dataset from Bristol Bay, Alaska, showed average sockeye mass declining from about 2.6 kg in the 1960s to about 2.3 kg in the most recent period studied, a roughly 10 percent drop over six decades.
- Pink (Humpback): The smallest Pacific salmon, generally 1.5 to 2.5 kg (3.3 to 5.5 pounds). Pinks have a strict two-year life cycle with only one winter at sea, so they simply do not have time to grow large.
- Atlantic: Wild Atlantic salmon returning after one sea winter (“grilse”) weigh about 2 to 5 kg, while multi-sea-winter fish range from about 4 to over 12 kg. Farmed Atlantic salmon, which account for the vast majority of Atlantic salmon on the market, are typically harvested at around 4 to 6 kg after roughly two to three years in sea pens.
These numbers describe typical adults returning to freshwater or being harvested commercially. Individual fish within every species vary widely, and the averages themselves have been shifting over recent decades.
Why Weight Varies So Much Within a Species
If you weigh a hundred sockeye from the same river in the same year, you will find a spread of a kilogram or more between the lightest and heaviest fish. Several factors drive that variation.
The single biggest factor is ocean age, meaning how many winters a fish spent feeding at sea before returning to spawn. A Chinook that spent four winters in the Pacific will dwarf one that came back after only two. Across all species, shifts in age structure explain about 88 percent of the year-to-year changes in average body size. In other words, when average salmon get smaller, it is mostly because more fish are coming back younger, not because fish of the same age are growing less.
Sex matters too, though the size gap between males and females differs by species. In many Pacific salmon populations, males are slightly larger on average because bigger males have an advantage competing for spawning access. In Atlantic salmon, the picture is complicated by the existence of early-maturing males called “jacks” or precocious parr, which are dramatically smaller than fish that went to sea.
Run timing adds another layer. Many rivers support multiple runs of the same species over the course of a season. Early-run fish often differ in average size from late-run fish of the same species in the same river, because the runs may represent genetically distinct populations with different life histories.
Salmon Are Getting Smaller
One of the most striking trends in salmon biology over the past several decades is that fish are shrinking. A comprehensive analysis of more than 12.5 million fish measurements from across Alaska found that all four major Pacific salmon species were smaller after 2010 than they were before 1990. Chinook showed the steepest decline, averaging an 8 percent reduction in body length. Coho declined about 3.3 percent, chum about 2.4 percent, and sockeye about 2.1 percent.
Because weight scales roughly with the cube of length, even modest length reductions translate into substantial weight losses. The Bristol Bay sockeye data illustrate this vividly: a 3 percent decrease in mean length corresponded to roughly a 10 percent decrease in mean mass, from about 2.6 kg down to about 2.3 kg.
The primary driver is the age-structure shift mentioned above. Salmon are returning to spawn younger than they used to, and younger fish are smaller fish. Changes in how fast fish grow at a given age do contribute, but across species and regions that contribution is secondary. In coho the growth-rate component is somewhat larger, explaining about 20 percent of the size decline on average, but in sockeye, Chinook, and chum it accounts for less than 8 percent.
Why are salmon coming back younger? The leading hypothesis points to competition. Pink salmon populations have boomed in the North Pacific, partly because of hatchery releases and partly because warming ocean conditions favor their short life cycle. When pink salmon abundance is high, sockeye and other species that share the same ocean feeding grounds tend to be smaller, likely because there is less food to go around. One analysis found that North Pacific pink salmon abundance had a particularly strong negative association with sockeye body size.
The consequences of shrinking salmon extend beyond the fish themselves. Smaller females carry fewer eggs, which reduces reproductive output per fish. Smaller carcasses deliver less marine-derived nutrients to the rivers and forests that depend on spawning salmon for fertilizer. And for fisheries, fewer pounds per fish means lower value per catch even when fish counts hold steady.
Farmed Versus Wild Atlantic Salmon
Most of the Atlantic salmon you find in a grocery store was farmed, and farmed fish grow considerably faster than their wild counterparts. In controlled feeding trials, farmed Atlantic salmon outgrew wild salmon by a factor of roughly 1.6 to 2.1, depending on the diet used. On a standard commercial salmon diet, farmed fish grew about 1.9 times as fast as wild fish, with hybrid crosses falling in between.
That growth advantage is partly genetic, the result of decades of selective breeding for rapid weight gain. But it also reflects diet. When all groups were fed a diet mimicking what wild salmon eat in nature, the growth gap between farmed and wild fish narrowed to 1.6 to 1. And when fed a nutritionally poor diet, growth for all groups dropped dramatically, with reductions as high as 83 percent compared to the standard salmon diet. The farmed fish still grew fastest, but the gap was smaller, suggesting that the commercial diet and the farmed genetics work together.
Commercial Atlantic salmon are typically harvested at about 4 to 6 kg after roughly 12 to 24 months in sea cages. One study used groups of farmed Atlantic salmon weighing about 5 kg each as a baseline for experiments on pre-slaughter starvation. That 5 kg figure is a reasonable reference point for a market-sized farmed fish. Wild Atlantic salmon that spend two or three sea winters feeding in the North Atlantic can match or exceed that weight, but they are much rarer in the marketplace.
What Spawning Does to a Salmon’s Weight
The numbers cited above describe salmon at or near their peak ocean weight. But salmon change dramatically once they enter freshwater to spawn. Pacific salmon stop eating entirely once they begin their upstream migration, and they may travel hundreds of kilometers while running on stored energy. By the time they reach their spawning grounds, they have burned through a large fraction of their body mass.
The energetic toll has been measured carefully in Atlantic salmon, which unlike Pacific species can survive spawning and return to the sea. During spawning, male Atlantic salmon lost about 35.6 percent of their somatic (body tissue) energy, while females lost about 25 percent. The total energy cost of spawning, including the energy invested in eggs and milt, was remarkably similar between sexes at roughly 51 to 52 percent of total pre-spawning energy stores.
For Pacific salmon the situation is even more extreme, because all five species die after spawning. A Chinook that entered the river at 15 kg might weigh less than 10 kg by the time it reaches the spawning gravel, its body wasted, jaws deformed, and skin deteriorating. This is worth knowing if you see weight figures quoted “at entry to freshwater” versus “on the spawning grounds.” The difference can be 20 to 40 percent of the fish’s weight, depending on how far it traveled and how long it waited to spawn.
How Water Temperature Shapes Growth
Temperature is one of the most powerful environmental controls on how fast a salmon gains weight, and this matters for understanding both wild and farmed fish. In a controlled study of Atlantic salmon parr reared at four different water temperatures, growth was highest at 14°C. Fish at that temperature had significantly higher weight gain and growth rates than fish at 10°C, 18°C, or 22°C. At 22°C, growth was poorest of all.
Feed efficiency followed a similar but not identical pattern. Fish at 10°C and 14°C converted food to body mass with similar efficiency, but at temperatures above 14°C, efficiency dropped significantly. In other words, warmer water made the fish eat more without gaining proportionally more weight, because a larger share of their caloric intake went to maintaining basic metabolic functions rather than building tissue.
In the wild, this translates to real consequences as ocean and river temperatures rise with climate change. Warmer rivers during migration force salmon to burn more energy getting to their spawning grounds. Warmer ocean temperatures can shift the availability and energy content of prey, increasing the metabolic cost of simply staying alive. One bioenergetic study of Atlantic salmon at sea estimated that adult fish needed between 331 and 813 kilojoules per day to sustain themselves, equivalent to roughly 5 to 11 small prey fish daily. The energy content of those prey items was the single most important factor determining how much food a salmon needed to maintain its growth.
From Whole Fish to What You Buy
When you buy salmon at a market, the weight on the label usually refers to a fillet or a dressed fish, not a whole round fish fresh from the water. Understanding the difference matters if you are trying to connect the species weights above to what ends up on your plate.
A “dressed” or “gutted” salmon has had its viscera removed but retains head, skin, and bones. Dressing typically removes about 10 to 15 percent of the whole-fish weight. Filleting goes further, removing the head, backbone, ribs, and belly trim. A bone-in fillet from an Atlantic salmon yields roughly 55 to 65 percent of the round weight, depending on how the processor handles the belly flap and pin bones. Skinless fillets yield less.
Pre-slaughter handling also affects the final weight. Farmed salmon are commonly starved for a period before harvest to empty the gut and firm the flesh. In one experiment, Atlantic salmon starved for 86 days lost 11.3 percent of their body weight, while fish that continued to be fed during the same period gained 26.3 percent. Commercial starvation periods are much shorter, typically a few days to two weeks, but even brief fasting causes measurable weight loss. This is one reason farmed salmon are harvested on tight schedules; every extra day without feed costs the producer money in lost yield.
Estimating Weight From Length
Anglers, biologists, and fisheries managers often need to estimate a salmon’s weight without a scale, and the go-to method is a length-weight relationship. The basic idea is straightforward: measure the fish’s fork length and plug it into a formula calibrated for that species. These formulas work reasonably well for ballpark estimates, but their accuracy has limits.
A study of Atlantic salmon found that simple single-measurement formulas could produce errors ranging from about negative 1 percent to as high as 72 percent when applied to individual fish. The problem is that two salmon of exactly the same length can differ substantially in girth, depth, and overall condition. To get predictions within about 2 percent of actual weight, researchers needed multi-factor equations that combined several body measurements.
For practical purposes, the standard length-weight formulas printed on fishing regulation cards or built into angler apps work fine for quick field estimates. But if precision matters, as it does for commercial grading or scientific monitoring, a single length measurement is not enough. The fish’s body condition, which changes with season, sex, reproductive state, and how recently it fed, introduces too much variability for length alone to capture.
Condition factor itself shifts throughout a salmon’s life. Atlantic salmon show notably lower condition at two life stages: just after emerging from the gravel as fry, and during the smolt transformation when they adapt to saltwater. For adult salmon in the ocean, condition tends to be relatively stable but varies with size, age, sex, and time of year. A fish measured on the same river in June and September could yield different estimated weights from the same length, simply because its body proportions change as it stops feeding and develops for spawning.
What Record Salmon Weigh
The heaviest salmon ever documented are Chinook, and the numbers are staggering relative to species averages. The all-tackle world-record sport-caught Chinook weighed 44.11 kg (97 pounds 4 ounces), taken from Alaska’s Kenai River in 1985. Commercial nets have reportedly landed Chinook over 54 kg (about 120 pounds), though records from net fisheries are less rigorously verified than rod-and-reel catches.
For Atlantic salmon, the rod-caught record stands at 35.89 kg (79 pounds 2 ounces), caught in Norway’s Tana River in 1928. Wild Atlantic salmon of that size are essentially unheard of today; modern multi-sea-winter fish rarely exceed 15 kg in most river systems.
Among the other Pacific species, record chum salmon reach about 15 to 19 kg, large coho can push past 14 kg, and exceptional sockeye have been recorded around 6.3 kg. Pink salmon records top out near 6.7 kg, which is almost three times the species average. These outliers are fascinating but deeply unrepresentative. The fish most people catch, buy, or study are far closer to the species averages listed at the top of this article, and those averages continue to inch downward as ocean conditions shift.