By Warren Lutz, Record Staff Writer
Sunday, March 5, 2006
STOCKTON - Historic low numbers of Delta smelt have a growing number of scientists fearing the fish is headed toward extinction.
If they do disappear, however, they won't be the first species to vanish from the Delta.
Grizzlies, perch and frogs are among the creatures that once called the Delta home but were pushed out when farming and development began changing character and texture of the 1,000-square-mile estuary as far back as 150 years ago.
Today, the environmental focus is on the smelt, a small. translucent blue fish whose abundance and health is often viewed as an indicator of the entire Delta's well-being. It's listed as a threatened species, but its numbers are so low and its lifespan so short - it only lives about a year - that scientists studying the Delta fear the species is close to being lost.
Yet over the past century, wildlife officials and environmentalists believe, dozens of birds, fish and other animals have vanished from the Delta. For many, they say, farming and levee construction destroyed their habitats. For others, it was pesticide poisoning or the introduction of non-native animals that took over their food supply.
But the actual losses are unknown.
"People didn't start actually cataloguing and keeping records until maybe 30 years ago. So it's hard to know," said Kim Delfino, state director of the environmental group Defenders of Wildlife.
It's generally accepted, however, that the Delta lost from 80 between to 90 percent of its native wetlands, much of which have been turned over to farming.
Many waterfowl and amphibians called those wetlands home, said Jeff Miller with the Center for Biological Diversity. Because of that, "there's obviously been casualties," he said.
According to wildlife officials and environmentalists, the lost Delta species include:
» Grizzly bears. Though traditionally found at higher elevations, the Delta was home to a number of grizzlies before farmers came along. They're not found anywhere in the state now, according to the California Department of Fish and Game.
» Red-legged frogs. The probable star of Mark Twain's "The Celebrated Jumping Frog of Calaveras County" is now only found along the coast and in low numbers in the Sierra. Environmentalists believe farm pesticides were the primary culprits. The frog is listed as threatened under the Endangered Species Act.
» Sacramento perch. The fish was harvested commercially from the Delta in the late 1800s but was last seen in the 1970s. Most likely it was killed off by predators or by non-native fishes, such as bluegill and striped bass, competing for food, according to University of California, Davis, professor Peter Moyle.
» Thicktail chub. The foot-long minnow was harvested by American Indians in large numbers but probably suffered the same fate as the perch, Moyle said. The last one was caught in Steamboat Slough nearly 50 years ago. It's now extinct.
» Bell vireo. The tiny gray songbird left the Delta for 60 years, but it may be back. A nesting pair were spotted last year in a patch of restored habitat along the San Joaquin River.
Some scientists say the Delta smelt could be next. One or more factors, including water exports to southern parts of the state, pollutants and invasive species, could be killing the fish, but there are no clear answers.
One group is studying the Delta's history with the hopes of learning how to prevent further losses.
Environmental scientist Robin Grossinger leads the San Francisco Estuary Institute's historical ecology program. He says most of the changes to the Delta were caused by its 1,600 miles of levees, some of which are 125 years old. Peat was scooped out of the marshy Delta and piled up into levees. Eventually, the islands inside dried out, and many islands were turned into cropland.
"It's a pretty dramatic change," Grossinger said. "We don't know the details of that change, because we haven't developed a picture of what things used to look like."
For some species missing in action, there may still be hope, Grossinger and others say.
UC Davis' Moyle is researching ways to reintroduce the Sacramento perch to the Delta. And another native Delta species that disappeared, the tule elk, is back at Grizzly Island near Fairfield thanks to a restoration program.
"It's all a matter of balancing what we need with what the species needs," said Defenders of Wildlife's Delfino.
"It's not going to be perfect," she added. "But maybe you're not going to be having the crisis we've been having in the Delta with the smelt."
Contact reporter Warren Lutz at (209) 546-8295 or wlutz@recordnet.com