He San Joaquin River It looks like a black mirror under the moonlight, but under its surface, the battle is fierce. Thousands of small salmonthe size of a little finger, swim in countercurrent, dodging voracious jaws and flowing through waters that seem more hostile every spring. His destiny is the Pacific Ocean, 350 miles away, but for most, it is a trip without return.
The panorama is bleak: Less than 5% of these brave youths manage to complete the journey. In the worst years, almost none achieves it. Hot water, dams that fragment the river and poor water quality were already declared enemies, but they are the Predators introduced by mansuch as black wolves and striated notices, which take the worst part of the mortal balance. “We know that these youth salmon are being decimated in their migration to the sea. We need to know why and how this happens, and if there are opportunities to take advantage of conservation practices, ”he explains Mike Gilmain author of the study and assistant professor in the Department of Ecology and Evolutionary Biology of the University of Colorado Boulder.
The epic migration of Chinook
The work, published in Ecology Lettersnot only reveals the danger that these fish face, but also their incredible Adaptation capacity. The researchers equipped 424 Chinook youth salmon and their predators with trackers To follow their movements for two months.
The data revealed a pattern they did not expect: the salmon swim Great distances through the center of the river during the nightwhen the predators sleep, and they take refuge near the shores at dawn and duskA, although this costs twice as much energy. The reason is simple: the predators, with their big eyes adapted to the gloom, have an advantage in those hours of the day.
He Salmon life cycle is a natural epic. They are born in the sweet waters of San Joaquin, where they pass their first year before starting the dangerous migration to the ocean. There they find the nutrients they need to mature and, years later, they return upstream to spawn, completing the circle of life.
However, time runs against him: the Chinook salmon population that migrate in autumn has fallen 90% in just two decadesaccording to the Department of Fishing and Wildlife of California. Of the almost 873,000 copies of 2002, there were hardly 80,000 in 2022.
The predators, especially striated notices, stalk in the center of the river during the day, where the currents are stronger and salmon could save energy. But This shortcut is a suicide. Therefore, these small fish have learned to move at night, taking advantage of the darkness and avoiding dangerous areas during the day. Even so, the Twilight is still a critical moment. “These fish seem to capture changes in environmental light,” adds Gil.
Reducing light pollution can help small salomnes
Research also suggests possible solutions to stop the debacle. Reducing light pollution in urban areas near the river could make a considerable difference. Artificial lights disorient salmon, making them vulnerable to attacks. A little one Adjustment in public lighting It could become a lifeguard for these tireless swimmers.
Far from being just a local problem, what happens in San Joaquin is a Reflection of the global problems of wildlife against human intervention. While the river continues its course, the history of these salmon is written every night, in the thin line between life and death. And although the end is still open, each night stroke is a cry of resistance.
#mortal #salmon #journey #survival #secrets #migration #edge #collapse
