Discovered in 1972, the largest salmon species ever known to have existed was Oncorhynchus rastrosus. This prehistoric salmon, which lived 5 million years ago, was up to 2.7 meters long and weighed over 180 kg. It inhabited the northwestern seas of North America during the Mesozoic era, where it ambushed its prey in both seas and rivers.
Recent studies have shown that Oncorhynchus rastrosus had tusk-like teeth that were used for various purposes such as competing with rivals, defending itself from predators, and digging nests. However, these tusks may not have been used for catching prey as believed earlier. Instead, they may have acted as water filters to feed on plankton, a theory supported by their large size and gill rakers.
The extinction of this giant salmon species is believed to have been linked to global cooling, which reduced the resources necessary to sustain its large bodies. Oncorhynchus rastrosus followed a migration pattern similar to modern-day salmon, hatching in freshwater, swimming to the ocean, and returning to freshwater to spawn and die.
Researchers plan to further analyze and explore the use of Oncorhynchus rastrosus’ tusks in the future. Understanding the behaviors and adaptations of this ancient giant salmon species can provide insight into evolutionary patterns and the impact of environmental changes on wildlife populations.