Stranger in a Strange Lake

At the visitors’ center at Clear Lake State Park, past the diorama of Pomo village life and the cutaway diagram of Mount Konocti’s volcanic innards, there’s a wall- mounted aquarium displaying some of the lake’s fish. Its inmates, two prosperous-looking bluegill sunfish and a runty large-mouthed black bass, were not what I had been expecting. These fish were no more native Californians than I am. I grew up with their kind in Arkansas and Georgia; you could say I grew up on their kind, dredged in cornmeal and pan-fried, with hushpuppies and coleslaw on the side. Where were the lake’s indigenes: the Sacramento perches and Sacramento pikeminnows, the blackfish, suckers, and hitches?
Some of those natives are still in Clear Lake, although in reduced numbers. Others are gone, and two species, the Clear Lake splittail and thicktail chub, are globally extinct. The splittail was not just native, it was endemic, found nowhere in the world except that single California lake. Once abundant enough to clog its spawning streams in the spring, its population crashed in the 1940s after those streams were diverted; 30 years later it had disappeared. “Not much is known about Clear Lake splittail,” says ichthyologist Peter B. Moyle, “because there was little interest in them until after they became extinct.”
The story of the splittail, and much more, is in the revised edition of Moyle’s Inland Fishes of California, recently published by University of California Press. It’s a truly magisterial book: exhaustively detailed, beautifully illustrated, and heavy enough to stun a sturgeon with. Moyle has spent years studying the state’s freshwater fish — not just the charismatic salmon and trout but all the sculpins, suckers, and sticklebacks — and he documents a facet of California’s biodiversity crisis that’s pretty much invisible to most of us. Redwoods and oaks, condors and grizzlies leave big holes in the ecosystem. But who notices the loss of a minnow?
We used to have quite a variety of minnows, most confined to the state’s waters. They ranged from rapacious predators like the meter-long pikeminnows to plankton feeders like the Sacramento blackfish and bottom browsers like the fathead minnow. Originating somewhere in Southeast Asia, where the greatest variety of species lives today, they followed long-vanished streams to North America shortly after the heyday of the dinosaurs, when the continents were differently configured. Some western minnows still have close relatives in China and Japan.
Other California fish came from North American stock, like the Sacramento perch, last survivor of an old lineage of sunfish. Now mostly an eastern family, sunfish were also abundant in the West before the great drying of the Miocene Era, five to ten million years ago. Another California endemic, the tule perch, descended from seagoing ancestors that colonized fresh water.
Together with the salmonids and other families, the minnows and perch formed complex ecological communities. Each aquatic environment — turbulent foothill streams, slow Central Valley rivers, lakes, ponds, estuaries — had its own assemblage of predators, omnivores, grazers, and scavengers. Clear Lake in its prime had a dozen native species, including a local strain of steelhead.
What happened to Clear Lake is emblematic of the fate of California’s native fish. There are 20 species in the lake now, but only a quarter of those are natives. The Sacramento and tule perch are outnumbered by exotic carp, catfish, sunfish, and bass. There’s even a thriving population of feral goldfish.
Although not the only factor, introduced fish species can be assigned a good deal of the blame for the natives’ decline. Sacramento perch, Peter Moyle explains, are vulnerable to egg predation by catfish, carp, and other exotics. The perch seem unable to coexist with their eastern relatives, especially black crappie, which have similar diets. Crappie and bluegill chase young perch away from the best feeding and hiding areas, into open water where they fall prey to largemouth bass. Competition from the introduced inland silversides may have finished off the Clear Lake splittail.
How did all these aliens get here? Thank the state Department of Fish and Game and its institutional predecessors, as well as fishermen who wanted to “improve” the sport. As far back as the 1870s, eastern fish were shipped west by train, in special aquarium cars, to be released in California’s rivers and lakes. Some were brought in as bait, or pest-control agents. (The inland silversides was supposed to eat the midges that boiled out of Clear Lake in enormous swarms; arguably a better idea than pesticides, but with the usual unforeseen consequences). Others hitchhiked in the ballast water of ships, joining the cioppino of exotics in San Francisco Bay.
We also moved native fish around. The Sierra was full of what would have been splendid trout streams if they had only had trout. Those streams, and many of the 4,000 formerly fishless high-country lakes, now have rainbows, introduced by packhorse in the 19th century and by the planeload in the 20th, as well as brook trout from the eastern US and Canada and brown trout from Europe.
But why, you might reasonably ask, is all this a problem? If biodiversity is an undeniably good thing, isn’t Clear Lake better off with 20 species of fish than it was with 12?
Clear Lake, the largest natural body of freshwater entirely within California’s borders, is an ancient place. Its fish and invertebrates had at least half a million years of coevolution to work things out. The lake the Pomo knew had three distinct fish assemblages: young minnows, perch, and sticklebacks in the tule-fringed shallows; offshore bottom-feeders that harvested the midge larvae; and open-water schoolers that fed on plankton, adult midges, and each other.
All that is gone, replaced by what Moyle calls an “amorphous conglomeration of species.” The lake, no longer a stable ecosystem, is subject to population booms and busts. Crappie, another Southern panfish, prospered at the expense of the Sacramento perch, then declined. Threadfin shad built up huge numbers only to be wiped out during an exceptionally cold winter in the early 90s. Reintroduced around 1997, their bodies littered the lakeshore during a massive die-off two years later. The fortunes of fisheating birds — grebes, cormorants, white pelicans — rose and fell with those of their prey.
If we had saved the native fish of Clear Lake, we would have preserved an aquatic community as distinctive in its own way as those of the great rift lakes of East Africa. It’s not too late, though, for other remnants of California’s piscine diversity. Moyle makes an eloquent case for fish conservation, not just for economic and scientific reasons but on moral and aesthetic grounds. These fish, he writes, are “part of a unique fauna that helps define why California is such a special place for humans to live. To understand and appreciate endemic fishes is to understand the dynamic and severe nature of California’s environment and to appreciate the evolutionary forces that created its present-day fauna. Such understanding can help us to live with the environment rather than constantly trying to control it.”

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