Many California freshwater fish are hanging on by just the skin of their fins, it seems.
This I learned from Dr. Jonathon Rosenfield, a fish conservation biologist with The Bay Institute, whose mission is the health of the San Francisco Bay and the 4600 square mile(!) watershed that feeds it. We breakfasted at an open air Mexican cafe to talk about California fish and their future.
Here are some stark statistics: of California’s 120+ freshwater fish species, 5% are extinct, 24% are listed as threatened or endangered, 13% are eligible for threatened / endangered listing, and 40% are in decline. Good gravy.
The most charismatic of the fish species are the Pacific runs of salmon and the rainbow trout. Interesting fact about these rainbows – some are adapted for permanent life in streams and some travel between oceans where they live most of their lives and streams where they spawn. The latter are termed “steelhead” here.
But more about the salmon right now, and in particular about salmon in the California Central Valley.
Salmon are beautifully adapted to use both the ocean and freshwater streams. As you likely know, salmon eggs are laid and hatch in coldwater streams. The fry eventually return to the ocean to grow to adults, and then make a one-way trip back to the stream in which they were reared to spawn and die. Their entire time in the ocean is spent putting on muscle and fat to make the upstream trip. During that trip they consume virtually no food.
I’ll write about the California Central Valley soon, but right now let’s just say the valley is 450 miles long and 50 miles wide, collecting water from the Sierras to the east and the coastal range to the west. The northern and wetter half of the valley is drained by the Sacramento River; the southern and drier by the San Joaquin. The rivers meet inland of San Francisco in the “California Delta” before discharging to San Francisco Bay.
Jon talked at length of the four runs of Chinook salmon that utilize central valley streams, many trying to get to the mountain headwaters in the Sierras. There’s the fall run, late fall run, winter run, and spring run. Each run is distinct and uses the stream system in a different way. Early settlers described the salmon runs as being so thick that one could traverse large rivers by “walking on the backs of salmon”. A stretch, certainly, but a nice description of their abundance. Salmon, Jon said, were a major food source for the ’49er gold miners. San Francisco grew from the Fisherman’s Wharf area and its abundant harvesting of salmon. Salmon (and other fish) were an important economic driver with the export of canned fish.
Salmon runs each numbered in the hundreds of thousands to millions. Now they’re diminished to a small fraction of their former presence.
What happened? The credible evidence suggests two principal things. First, water diversions. The San Joaquin is dry in a 50 mile mid-stretch, and the fish can’t hitchhike. Only half the water that used to flow to San Francisco Bay now gets there, the rest is diverted for municipal/industrial use (20%) and crop irrigation (80%). Second, dams and reservoirs keep the fish from reaching spawning habitat. The dams and reservoirs have the lethal effect of warming water so much that salmon eggs can’t survive.
Dr. Rosenfield puzzles on a way to move forward; How to get more water in streams to save fish from going extinct. But it appears to be an uphill battle.