Salmon are known for their leaps out of the water, a common sight during their upstream migrations. These acts are not random; they serve several purposes connected to the salmon’s survival and life cycle.
Overcoming Obstacles
A primary reason salmon jump is to navigate physical barriers during their upstream migration to spawning grounds. These obstacles include natural formations like waterfalls and rapids, or human-made structures such as dams and culverts.
Atlantic salmon can leap as high as 12 feet, while Chinook, Coho, and Sockeye salmon typically jump around 8 feet. This requires strength and precise timing to utilize the water’s hydraulic forces. Their streamlined body shape aids in reducing drag, allowing them to gain the necessary speed for liftoff.
Salmon often position themselves beneath turbulent water at the base of an obstacle, using the upward pressure from falling water to boost their initial leap. This combination of power and understanding of water dynamics enables them to overcome barriers. Navigating these obstacles is important for reaching their spawning sites.
Evading Predators
Salmon jump to escape predators. When faced with threats from animals such as bears, eagles, ospreys, seals, or larger fish, a sudden leap can provide a momentary advantage.
By breaching the surface, salmon create an unpredictable movement that can disrupt a predator’s attack strategy. While airborne, the salmon might alter its trajectory before re-entering the water, making it harder for the predator to anticipate its next move. This brief escape can be enough for the salmon to dart away to safety.
Relief from Irritants
Salmon also jump to alleviate discomfort from external irritants. One reason is to dislodge parasites like sea lice, which they often pick up in marine environments. Studies show that salmon allowed to jump can have fewer sea lice compared to those prevented from doing so. It may take numerous leaps for a salmon to remove these parasitic attachments.
Beyond parasites, jumping can help salmon clear their gills of debris, silt, or other particulate matter. A forceful exit and re-entry into the water can “shake off” unwanted particles, improving their respiratory efficiency. This behavior contributes to the comfort of the fish.
Other Potential Purposes
While less proven, salmon jumping may serve additional purposes beyond obstacle navigation, predator evasion, and irritant relief. Some observations suggest jumps could be a form of communication among salmon, perhaps signaling their presence or readiness to spawn. This might also include territorial displays, where a jump serves as a visual assertion of dominance or claim over an area, especially in crowded spawning grounds.
Another hypothesis suggests some jumps may relate to the salmon’s internal buoyancy regulation, specifically to refill their swim bladders with air. The Tlingit culture also suggests salmon might jump to better observe their surroundings, gaining a visual orientation of both water and land. While these behaviors are under scientific investigation, they highlight the nature of salmon jumping.