An estimated 2,343 coho salmon smolt migrated this spring from Olema Creek, an amount lower than last year but double what was expected, according to the Point Reyes National Seashore. Though an average number compared to all years since the park started trapping smolt in 2004 to collect data, the pleasantly surprising number indicates to biologists that the endangered population is persevering despite severe drought conditions. “It’s fewer fish than we saw last year, in terms of smolt leaving, but it’s higher than our lower years,” said Michael Reichmuth, a fisheries biologist with the National Park Service. “They were fairly healthy fish, and I think they have a good chance of surviving out in the ocean so long as they can find food.” Mr. Reichmuth attributed the healthy number to work done to stabilize creek banks and mitigate human influences along riparian corridors. Salmon enjoy three-year life cycles, and each year a new group of salmon, called a “cohort,” spawns between November and January. The juvenile smolt then emerge from their nests in March; they are reared in the creek during summer and stay through winter. In spring, the smolt cohort migrates to sea—in the case of this population, down Olema Creek into Tomales Bay, and from there into the Pacific Ocean. To get an estimate of how many fish lasted to the migration period, the park sets up a trap near the mouth of Olema Creek. As the smolt move downstream, a net funnels them into what’s called a “live box,” which during the peak migration times in late April and early May are checked twice daily. Park biologists and volunteers count, weigh and measure the smolt, some of which are also implanted with a small radio tag that acts like a lifetime barcode to track their movements. The tagged smolt are relocated upstream and, when they return back down, give biologists an idea of how efficiently the traps are working. Mr. Reichmuth attributed the unexpected higher count to a larger amount of smolt spawning in Olema Creek’s many tributaries, which biologists did not survey over the summer—when they snorkel-survey the smolt in the creek. He also surmised that restoration efforts undertaken by the park to improve water quality by fortifying riparian corridors and mitigating human-induced changes were opening up additional areas for the coho to spawn. “Because we’ve provided a larger riparian corridor in the tributaries, we still have water in standing pools, even in a drought year like this,” he said. Coho salmon, which once totaled in the hundreds of thousands in California, dwindled to near-extinction levels and, in 2005, were designated as endangered by the federal government.