The fish are jumping, but in appar-ently dwindling numbers, as the spawning season for salmon nears prime time in the Northern San Joaquin Valley.
Traditionally, most spawning activity on the Stanislaus, Tuolumne and Mer-ced rivers occurs during the second and third weeks of November.
"So far, the numbers are very low," said Tim Ford, an aquatic biologist with the Turlock and Modesto irrigation districts. "There's no way to know for sure, but right now, it looks like it could be a bad year."
By Oct. 30, just 205 chinook were counted on the Stanislaus River. The fish are individually photographed and counted as they pass through a special weir.
Last year, at the same spot, 996 salmon had been counted as of Oct. 30.
On the Tuolumne River, meanwhile, Ford said 25 to 30 salmon were spotted Oct. 27 near La Grange, during an irrigation district survey.
Preliminary count figures weren't available for the Merced River. But Tim Heyne of the California Depart- ment of Fish and Game said fewer salmon are returning there, too.
"It appears," Heyne said, "we're getting about a third of the fish as we did last year."
Heyne and Ford said the numbers still could show improvement because "it's still very early."
Preliminary salmon counts also are showing fewer fish returning to the Sacramento, American and Feather rivers.
"It's the same thing almost everywhere on the Pacific Coast," said Doug Demko of FishBIO, a consulting firm with offices in Oakdale and Chico. "On the Stanislaus, we're down about 90 percent from four years ago.
"But this year, definitely, is the most concerning."
Demko and other experts believe changing conditions, including warmer water temperatures in the northern Pacific Ocean, could be behind the apparent decline.
Salmon thrive in colder water.
For years, conventional wisdom in the Northern San Joaquin Valley has been that more water flowing through rivers during the springtime would lead to larger numbers of salmon returning to spawn.
But that paradigm could be shifting.
Before 2006, "we had several good water years, but the (salmon) numbers are down," said Modesto Irrigation District spokeswoman Kate Hora, "so something else must be going on."
Walt Ward, the district's assistant general manger for water operations, said the myriad problems afflicting the delta could be factors.
"Predatory striped bass, water quality and temperature problems, the delta pumping -- there's probably no one single cause."
MID General Manager Allen Short, for one, believes predation has been underrated as a possible cause for the apparent decline in salmon returning to spawn.
"Things are out of balance (in the delta)," Short said. "Salmon are getting slaughtered by stripers."
Ward said water flows into the Tuolumne from Don Pedro Dam are regulated by the federal government with an eye toward preserving chinook salmon.
"You can only do so much," Ward said, "and even if you do it perfectly, you still may not meet your objective."
Demko agrees that predation -- striped and black bass feeding on baby salmon, also referred to as smolt -- likely has been underrated as a problem.
But he said he believes the conditions in the Pacific Ocean are the primary reason behind this season's so far paltry salmon numbers.
"Ocean conditions are critical," he said.
Bee staff writer Michael G. Mooney can be reached at firstname.lastname@example.org or 578-2384.