The Bay Delta's Waning Giant: White Sturgeon | KCET
The Bay Delta's Waning Giant: White Sturgeon
An explanatory series focusing on one of the most complex issues facing California: water sharing. And at its core is the Sacramento-San Joaquin Bay Delta. Stay with kcet.org/baydelta for all the project's stories.
San Pablo Bay is shallow, a 90 square mile dinner plate full of seawater. Aside from a deepwater shipping channel running west to east off the Contra Costa County shore, which gets about 50 feet deep off Point Pinole, the majority of this northern lobe of San Francisco Bay is less than 10 feet deep at low tide. A six-foot person attempting to walk across the bay from the Sonoma County shore could make it about a third of the way at a very low tide before donning a snorkel.
This shallow sea blurs the boundaries between land and water. Low tides can expose a hundred feet of mudflats; high tides chase rails out of cordgrass and pickleweed. One day I took my sea kayak out from the south shore in a heavy wind, and the waves were big enough to dump me; when I stood up beside my boat, the water came up to my waist a quarter mile from shore.
But ten or twelve feet of turbid saltwater is enough to hide secrets. Beneath the surface of San Pablo Bay lurk leviathans; huge, pallid fish with ancient, prehistoric-seeming features. I don't mean sharks. Though great whites do poke their noses into San Francisco Bay from time to time, they don't linger. It's the white sturgeon, Acipenser transmontanus, that takes first prize as the Bay Delta's largest resident fish.
The white sturgeon doesn't have any serious competition for the title. In fact, it's the largest freshwater fish in North America. Mature white sturgeon can reach weights of 1,300 pounds, and lengths of between 12 and 20 feet. That's significantly larger than the white sturgeon's close cousin the green sturgeon, and far bigger than any other potential competition for the Bay Delta's largest fish.
Other sturgeon, the Bay Delta's green sturgeon included, will spend much of their lives in the open ocean, coming back into freshwater to spawn. The white sturgeon's different. In the Bay Delta, and in other rivers and estuaries up the Pacific Coast to Alaska, white sturgeon adults stay in estuaries where freshwater and salt mix. Farther north this may mean remaining near the mouth of a river, in the mixing zone where freshwater dilutes seawater. In the Bay Delta, adult white sturgeon spend a lot of time in San Pablo Bay.
There, and in Suisun Bay and other places in the Bay Delta where waters are rich with suspended sediment and nutrients, white sturgeon drift about below the surface, generally letting their food come to them; that food may be swimming past, or drifting. An adult sturgeon's diet generally consists of small crustaceans, mollusks, fish eggs, small fish, and occasional dead animals or pieces thereof -- including, according to one report, a domestic cat, presumably deceased well before the sturgeon found it.
The largest sturgeon ever recorded caught in the Bay Delta watershed, according to perhaps less than reliable reports of the time, was a 16-foot, 1,500 pound fish hauled out of the Sacramento River in the 1880s, caught on a meat hook with a rabbit as bait. (The largest thoroughly documented white sturgeon caught by an angler in California was a 468-pound adult landed in 1983.)
Younger sturgeon don't indulge in quite as lavish a diet, favoring opossum shrimp when they can find them, as well as the invasive Amur River clam once they're big enough to eat them. In their first year, white sturgeon in the Bay Delta may grow as long as 11 inches. Growth slows down in subsequent years. At six or years of age a healthy white sturgeon might have reached three and a half feet in length; a six-footer is likely a quarter century old.
White sturgeon are anadromous, like their green cousins: they head for freshwater to spawn. Adult sturgeon can spawn many times over the course of their lives, starting at about eleven or twelve years of age for females, and a couple years earlier for males. Adults seem to wait about five years between spawning runs. Before the dams went in on the Delta's tributary rivers, white sturgeon likely navigated as far up many of the larger rivers as they could, given their occasionally immense size.
Much about their spawning remains a mystery, but they seem to prefer deep pools with a gravel bottom; females release their eggs, often in huge numbers, and males fertilize them. Fertilized sturgeon eggs are sticky, and that helps them adhere to the bottom until the larvae are ready to hatch out.
Sturgeon reproductive success is strongly tied to two factors: abundance of mature, reproductively experienced adults (older sturgeon make more babies), and the amount of fresh water in the system. Higher freshwater flows mean more year-old sturgeon coming down into the estuary, and those flows encourage spawning adults upriver to spawn as well. That has contributed to an historic "boom and bust" cycle in white sturgeon numbers, in which "production" in a boom year -- usually following a flood winter in the Bay Delta watershed -- might be many times that of the years before and after.
Of course, that's in a system where the sturgeon have been reeling from two huge monkey wrenches thrown into its historic life cycle. The first, predictably enough, is our having built obstacles between sturgeon in the Bay Delta and the bulk of historic spawning in the form of the same giant dams and other blockades that hinder spawning migrations of salmon, steelhead, and other fish.
The other monkey wrench? We nearly killed them all.
In the last four decades of the 19th century, an unregulated sturgeon fishery came close to wiping out the white sturgeon population in the Bay Delta watershed. A commercial fishery started in the Bay in the 1860s; at its peak, in 1887, that fishery caught 1.66 million pounds of sturgeon for sale in the Bay Area's swelling cities. That boom was followed closely by a bust. In 1895, according to fisheries scientist Peter Moyle in his book "Inland Fishes of California," the sturgeon haul had dropped to 300,000 pounds, and less than 200,000 pounds in 1901.
In that year, the California Board of Fish Commissioners closed both the commercial and sport fishery for sturgeon, hoping to stem the decline in sturgeon numbers. A few tentative reopenings over the next few years showed the population had not recovered. In 1917 the Board, renamed the California Fish and Game Commission just eight years earlier, closed the state's commercial white sturgeon fishery permanently -- a closure still in effect at this writing, 98 years later.
That closure also covered the sport fishery, but in 1954 the Commission reopened the recreational fishery, with a bag limit of one fish per angler per day, and a minimum size limit of 102 centimeters: about three feet, four inches. That fishery proved extremely popular, though it mainly relied on the unsportsmanlike practice of "snagging," which was banned for sturgeon in 1956.
The snagging ban put a damper on the sturgeon sport fishery for several years. But in 1964, anglers discovered that sturgeon would eagerly take shrimp as bait, and the take of white sturgeon from the Bay Delta grew.
In 1976, when the first edition of "Inland Fishes of California" was published, author Peter Moyle expressed optimism for the white sturgeon's future, saying "the present managed sport fishery promises to yield continuous returns for years to come." Nearly forty years later, fisheries biologists aren't so sure. Though sturgeon numbers declined steeply in the years after anglers discovered the shrimp bait method, they seemed to stabilize during the 1970s. And then, in the 1980s, the numbers started to crater. By 1993, it took twice as much time for a recreational angler to land a sturgeon as it did in 1983. That was a solid indication that something was going very wrong with the sturgeon fishery.
To compensate, the Fish and Game Commission enacted maximum size limits on sturgeon in the late 1980s, and has adjusted them throughout the years since, usually downward. Current regs require that white sturgeon longer than 60 inches, as measured from the tip of the nose to the middle of the tail, not be removed from the water. Fish under 40 inches are off-limits as well.
The reason for the maximum size limits is, as we said above, that older sturgeon make more babies. By skimming off the larger adults, the sport fishery had been weakening the species' ability to sustain itself through droughts, which relied largely on those sexy older fish getting through the drought to the next flood year in sufficient numbers to make a whole lot of babies.
The last three boom years for white sturgeon, in 1995, 1998 and 2006, followed exceptionally wet winters. Both those booms were minuscule compared to the boom of 1982, after a winter when most Californians learned the phrase "El Niño," when intense rains collapsed hillsides and cliffs across the state. As we become more accustomed to drought, Californians point to 2011 as the last time we had a "typical" water year, but sturgeon production during 2011 was less than a sixth what it was in 1998.
Another way of looking at it: in at least 14 of the years since 1987, production of newborn white sturgeon has been essentially zero. The boom years in between haven't just become less frequent: they're a lot less "boomy."
The sport sturgeon fishery isn't responsible for the drought. But it may be hindering the sturgeon's ability to take advantage of the next moderately wet year to make more young sturgeon.
And it would seem there are some sport anglers who aren't playing by the rules. The Fish and Game Commission has set an annual limit of three fish to help preserve the sturgeon; anglers are required to buy a "report card" with three detachable tags before fishing, then fill out and submit a tag for each fish caught. In 2013, the Commission decided it had to change the design of those tags: anglers had been filling out tags for each sturgeon caught just in case they were stopped by a game warden, then -- if no warden took the tags -- erasing the tags and using them for additional fish. The California Department of Fish and Wildlife (CDFW) now uses tags that are harder to cheat with.
CDFW also tags the fish themselves, and since 2010 anglers who catch a tagged sturgeon have been legally required to submit that tag to CDFW. Compliance is sluggish. CDFW has experimented with giving cash rewards to anglers who return those tags, which boosts participation somewhat.
It would seem to behoove anglers to play by the rules. The tags are there to let CDFW track how many fish are being caught, so that they can attempt to manage the fishery to maintain the species. Cheating interferes with the science...which would seem just as unsportsmanlike as snagging, when you get right down to it. The murky waters of San Pablo Bay may conceal secrets, but it'll be hard to hide the fish if they're not there anymore.
For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.
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