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| San Joaquin delta, credit: Alamy |
Because of human exploitation, Chinook salmon disappeared from central California's San Joaquín River some sixty-five years ago. For thousands of years Chinook made a twice yearly trip in spring and fall over three hundred miles from the Pacific to Sierra Nevadas. Over two centuries the river was appropriated for agriculture. Dam building for irrigation purposes caused the river to run dry in places by 1940, disrupting the salmon runs. This year, twenty-three Chinooks made the spring migration upstream. Not a lot of fish, considering each female can lay 4200 eggs, but it is a milestone for conservation.
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| released salmon fry, credit NY Times |
It took eighteen years of litigation against the federal government to finally settle in 2006 a lawsuit brought by the National Resources Defense Counsel (NRDC). The agreement calls for salmon to be restored to "good condition", and minimize water diversions. The state and federal government is planning to spend $650 million to restore flow, wetlands, and fish populations to the San Joaquín. The twenty-three salmon caught and released represent the first spring run of Chinook up the river since 1950. Conservationists hope these pioneers are the a sign of recovery despite California's epic drought that dried up the river and destroyed riparian wetlands. Scientists caught the salmon in nets and took samples before returning them to upland river stretches where salmon historically spawned. The sampled salmon come from a cohort of 38,106 juveniles release in the upper San Joaquin in March 2017; they probably represent about 100 returning fish helped by the heavy winter rains and snow that ended the drought cycle.
The river is now continuous and other species are also returning: sturgeon, lamprey, water birds and fish species. So there are reasons for optimism, but human help overcoming obstacles in the river is not a sustainable model. Part of the river restoration project includes building rock lined ramps that Chinook and other fish can swim up on their way to spawning grounds. Reconnecting the Chinook with their cool water spawning grounds will become even more important as climate and water temperatures rise.
