Are Salmon Cannibals? The Surprising Truth About Salmon Eating Their Own Kind

Salmon are one of the most iconic fish species. These large, powerful fish make epic migrations between the ocean and freshwater rivers to spawn. During spawning season, thousands of salmon crowd into rivers, fighting their way upstream to their spawning grounds. This spectacular natural phenomenon has fascinated people for millennia.

However, some disturbing salmon behaviors have been observed during the frenzied spawning ritual Salmon have been seen attacking, biting, and even eating other salmon! This gruesome practice has led many people to ask

Are salmon cannibals?

The short answer is yes, salmon sometimes do eat other salmon. However, the full story is more nuanced. Keep reading to learn the truth about this surprising salmon behavior.

Why Do Salmon Attack Each Other?

Salmon are not intentional cannibals. They do not seek out and consume their own species by choice. However, during the chaos of the spawning run, salmon are focused on only one thing – reaching the spawning grounds. They will attack ANYTHING that gets in their way, including other salmon.

Salmon runs occur when thousands of sexually mature salmon all return to their natal rivers at the same time. This results in a massive bottleneck as hordes of fish try to swim upstream through shallow, rocky rivers. Salmon will often bite and nip other salmon to get them to move out of the way. These attacks sometimes cause fatal injuries. The dead fish may then be eaten by other hungry salmon still fighting to migrate upstream.

Additionally male salmon undergo physical changes during spawning season. Their snouts and jaws elongate and become hooked so they can fight other males to establish dominance. Females also become more aggressive before spawning. Their bites can puncture the flesh of other salmon.

So salmon do not intentionally choose other salmon as prey. But during the chaos of the spawning run, attacks meant to clear the path or assert dominance can sometimes escalate to cannibalistic behavior.

Does Eating Other Salmon Benefit Them?

Eating other salmon during the spawning run does provide some nutritional benefits.

Salmon stop feeding once they enter freshwater rivers to spawn. At this point, they depend entirely on fat stores to fuel their arduous journey upstream. Access to additional protein in the form of other salmon can help sustain migrating fish.

Female salmon also stand to gain more by consuming other salmon. Female bodies undergo tremendous changes before spawning Eggs rapidly increase in size, number, and nutrient density Eating extra protein from other salmon helps fuel this explosive egg production.

That said, salmon are not adapted to routinely consume other salmon. Their digestive systems are designed to process other prey like smaller fish, squid, and crustaceans. Eating other salmon provides limited nutritional value and is simply an opportunistic behavior.

How Often Does This Happen?

Cannibalism among salmon is relatively rare. Though frenzied attacks are common during spawning season, most bites do not result in fatalities. Additionally, the deceased fish are quickly washed downstream, making consumption unlikely.

However, a few situations can lead to increased rates of cannibalism:

• Overcrowded rivers: If too many salmon return to spawn, the rivers become overcrowded. This leads to more frequent attacks and fatalities. With more dead salmon available, consumption increases.

• Low water levels: Salmon migration is easiest when rivers are high with autumn rains. In drought years, low water levels create more congestion and fighting.

• Hatchery fish: Many salmon runs are now supplemented with hatchery-raised fish. These fish may be more aggressive and less well-adapted to natural spawning behavior.

• Mixed species: When multiple salmon species share spawning sites, they may be more aggressive toward each other. Chum salmon are particularly violent defenders of spawning sites.

Overall though, biologists emphasize salmon cannibalism is an anomaly rather than the norm. It occurs as an indirect result of the competitive spawning process, not as a deliberate feeding strategy.

Are Farmed Salmon Fed To Other Salmon?

Commercial salmon farming operations feed dried, processed salmon products to their fish. This seems cannibalistic at first glance. However, the dried salmon bits contain only minimal traces of DNA. The extensive processing renders the original source unrecognizable.

Salmon farmers assert that farmed salmon do not recognize these feeding pellets as coming from other salmon. The lack of bones, scales, and other identifiable bits may contribute to this. Additionally, farmed salmon are domesticated animals that are not adapted to identify or consume whole prey.

Nonetheless, the practice of feeding factory-farmed salmon the ground up remains of other salmon raises both ethical and environmental concerns. Many consumers balk at the idea. But most experts maintain that farmed salmon are unlikely to recognize the salmon meal pellets or exhibit cannibalistic behaviors.

Key Points About Salmon Cannibalism

• Salmon do sometimes consume other salmon, but true cannibalism is rare
• Attacks happen while migrating as salmon compete to reach spawning sites
• Eating other salmon provides some nutritional value
• It occurs more with overcrowding, low water, and hatchery fish
• Farmed salmon are fed dried salmon meal but likely don’t recognize it as cannibalism