Annual Sacramento Index (SI) including harvest and escapement, and the 2015 PFMC forecast of SI
This illustrates dramatic rises and drops in California’s Central Valley salmon population over the years. Survival of California’s iconic salmon, as well as the $1.4 billion salmon industry, which supports 23,000 jobs in most coastal communities in Northern California, is in serious danger of collapse.
Because salmon are anadramous (they live part of their lives in fresh water, part in the ocean), they show us strong signs of the health or damage to both freshwater and marine environments. When dams were built, Central Valley salmon lost about 80 percent of their historic spawning habitat. But even before the dams, copious amounts of dirt and sediment created by mining operations buried much of the gravel Central Valley salmon need for spawning. Instead of returning to quality gravel beds, salmon returned to find their home streams cemented in with mud. Commercial fish traps in the rivers in the late 1800’s, further reduced their numbers.
In the 20th Century, the construction of dams on every major Central Valley salmon river cut off access to most historic salmon habitat.
Shasta Dam (Sacramento River), Oroville Dam (Feather River), Nimbus Dam (American River), Friant Dam, (San Joaquin River)
At the same time Central Valley salmon rivers were largely straightening and river banks were armored with heavy rock. This denied baby salmon access to the banks, edges, and floodplains where they’d historically found rich feeding grounds and safe refuge to hide from predators. We see the damage done to baby salmon from the armoring and straightening of river beds, from choking the life out of banks and floodplains with dikes and levees.
Miles of river banks have been straightened and armored with rock denying baby salmon places to feed and shelter
Dams stopped much of the spring rain and snow runoff needed to carry baby salmon from the Central Valley to the ocean.
Today, only in the wettest years, when reservoir operators are forced to release water to prevent over topping of dams, is there the type of spring runoff baby salmon evolved to take advantage of. Gone too is the natural turbidity created by sediment suspended in runoff that provides natural camouflage baby salmon need to hide from roving predator fish and birds.
Instead, all too often during spring, rivers run slow and clear and baby salmon are massacred by predators.
Dams and water diversions in our rivers give a heavy advantage to predators that eat baby salmon
Today in the Central Valley salmon try to spawn in rivers that are sometimes too hot to successfully incubate fertilized eggs. Elevated river temperatures kill incubating salmon eggs when they exceed 56 degrees.
Salmon eggs die when river temperatures exceed 56 degrees
In early October fall run salmon lay eggs in nests (called redds). The redds are often left high and dry and killed when water managers suddenly reduce reservoir releases later in the fall when agricultural demand for water is over for the year.
Massive water diversion intake pipes dot Central Valley rivers. They suck in untold numbers of baby salmon, some of which wind up deposited in agriculture fields as part of irrigation water. In recent years this problem has been recognized with the bigger diversions now screened to avoid this loss. But many smaller unscreened diversions still exist and are easy to spot all along the Central Valley rivers.
Both of California’s Central Valley major rivers, the Sacramento and San Joaquin, meet in one large Delta some 60 miles east of the Golden Gate Bridge. Decades ago the state made a decision to tap the Delta waters and export them south to southern California cities and to dry desert lands in the western San Joaquin Valley for agricultural use. This decision was made with no thought about the harm this would do to salmon.
Top graphic shows natural out migration route for baby Central Valley salmon. Big fish icons near state and federal pumps represent predators that eat baby salmon.
Second graphic depicts how baby Central Valley salmon are pulled off their natural migration course when the state and federal Delta pumps are turned on. When this happens, most are lost to predators in interior Delta.
The National Marine Fisheries Service (NMFS) recognizes the pumps as salmon killers and has required restrictions on pumping to minimize damage to winter and spring run salmon, both protected under the federal Endangered Species Act. NMFS estimates that as much of 90 percent of baby salmon pulled off their natural migratory route to the bay and ocean are lost to predators in the interior Delta or when pulled into the pumps. Put differently, for every baby salmon captured at the pumps, nine other likely died from the effects of the pumps.
Of the fish captured at the pumps, most are dumped back into the Delta at locations where predatory fish have become accustomed to feeding. Changes in the river bottom throughout the Delta leaves deep scour holes where predators congregate and feast on baby salmon. Other problems beset Central Valley salmon.