At one time California’s Central Valley witnessed the return of adult Chinook salmon 3/4 of a million strong. By 2007, the returning population making the trek from the Pacific Ocean through the San Francisco Bay and spawning in the Sacramento River had declined to 90,000. And with the season ending in 2008, the numbers had managed to only reach 8.8% of their former number. Did I mention the Chinook salmon population of 750,000 I am referring to was a mere 6 years ago in 2002?
Yes, in half a decade the Chinook population has plummeted by 92% and set a new record for an all-time low of wild and hatchery salmon to successfully return to their spawning waters. Blame for the rapid decline has many people pointing many fingers, but when we boil it down to a common cause mankind is left holding the bag.
Agricultural water pumps, ocean and climate change, California’s system of canals, pollution and dams are bandied about and have even instigated a lawsuit against the National Marine Fisheries Service to protect the salmon. Speaking of the NMFS, they specifically state the cause of the decline as “Water storage, withdrawal, conveyance, and diversions for agriculture, flood control, domestic, and hydropower purposes.”
These artificial features now inhabiting natural landscapes are preventing access to spawning grounds, and directly affecting mortality of adult and juvenile salmonids.
The NMFS expands on this pacific salmon issue and recognize that “Modification of natural flow regimes have resulted in increased water temperatures, changes in fish community structures, depleted flows necessary for migration, spawning, rearing, flushing of sediments from spawning gravels, gravel recruitment and transport of large woody debris. Physical features of dams, such as turbines and sluiceways, have resulted in increased mortality of both adults and juvenile salmonids.”
As is so common in the wildlife, environmental realm, we are faced with an understanding of the cause of the problem, but fail to take corrective actions and mitigate the problem.