California can do a lot to keep its native salmon and other fish species going through this record drought, and through the inevitable worse ones to come, according to a leading fisheries biologist. But it's going to take hard work and hard choices, and Californians will need to rethink the way the state manages water, he says.
In a post published Monday on UC Davis's California Water Blog, Peter Moyle, a biologist who's widely regarded as the dean of California fisheries science, details both short-term and long-term measures he thinks will be needed to keep California's native fish keeping on.
In the short term, Moyle recommends a set of what emergency room doctors might refer to as "heroic measures" to get salmon and other fish through the present drought. But it's the long haul that will take the real work.
Moyle, associate director of UC Davis's Center for Watershed Sciences, has been studying California's fish for more than four decades. He points out that 82 percent of the state's native fish species live only in California, or the immediate vicinity.
Even fish species like the chinook salmon, which technically speaking ranges from California through Alaska to Siberia and Japan, are so-fine tuned in an evolutionary sense to local conditions that an extinction in California's chinook population might as well be a global extinction.
"Our California populations of steelhead trout and Chinook salmon are uniquely adapted for local conditions," writes Moyle. "If spring- and winter-run Chinook were to disappear from the Central Valley, we could not replace them with salmon from Alaska. They simply could not survive here."
Which makes this drought troubling in a global sense: most of the fish species in the state are unique to some degree, and if we lose them here we lose that uniqueness for good.
Even before the drought, California native fish were in trouble. Almost a quarter of the state's 122 native fish species are listed as threatened or endangered: 23 percent of the total. Another 22 percent have been recommended for listing, and more than half the remainder are considered "vulnerable."
In other words, of those 122 native fish species, 89 are at risk due to changes in their habitat over the last 160 years. Moyle and his colleagues have described that risk as "headed for extinction by 2100 if present trends continue."
And included in those 89 species are most of California's salmon and trout.
The irony is that California's chinook salmon have evolved to deal with wildly variable conditions. They can shift the timing of their spawning runs to reflect river levels. Their several historic seasonal runs per year can overlap. They can spawn at two years old, or at six years old, or somewhere in between. But that very flexibility that has allowed chinook to weather droughts worse than this one makes them more vulnerable to the relatively inflexible water management system we've built in California.
So how do we ease our fish through the current drought? Moyle suggests a few different "heroic measures," including paying farmers to let fields go fallow so that warm runoff doesn't degrade stream quality, stepping up enforcement of illegal fishing and raising lower size limits for commercial fishers, and even trucking fish from vulnerable locations to others with more water. Moyle also suggests that managers may have to make some hard, "triage"-style choices for allocating environmental flows in the state's rivers, choosing which species to boost to the possible detriment of others that could have used the water at a different time.
Long-term, the task is even greater. Moyle points out that in order for salmon populations to recover from the blow this drought has already done them, we're going to need to change our water management policies drastically. Useless dams like the Matilija Dam on the Ventura River, which provides neither water nor power, will need to come out. Fish hatcheries will need to shift their focus to preserving wild runs of fish. Dams not suitable for removal will need too be managed to ensure well-timed environmental flows that provide water both to spawning adults and to the young they produce.
And some streams may need to be managed as salmon sanctuaries, with fishing, development, and changes to streamside vegetation strictly limited.
That all constitutes a big shift for California water policy to help salmon recover from the drought. The upside is that many of the state's other fish species will likely benefit as well.