If timing is everything, then now is the time to see coho salmon and river otters at the Inkwells on Lagunitas Creek in Marin County. You might even see fish sex.

On Friday, wildlife watchers saw more than 40 salmon jumping through the series of short pools and drops, plus a family of river otters. Nearby they saw the fish spawning.

A guided walk is scheduled for noon to 2 p.m. Saturday, starting at Samuel P. Taylor State Park along Sir Francis Drake Boulevard. To reserve a spot, register at www.seaturtles.org — click on “programs,” then “salmon.”

“We’ve seen some really big fish, maybe even up to 2 feet long,” said Melissa Angel, who works for SPAWN, which stands for Salmon Protection and Watershed Network, a subsidiary of the Sea Turtle Network. A $15 donation or $30 membership is suggested for the guided walk.

The five best spots to see the salmon, now bright red in spawning colors, are: the Inkwells at Shafter Bridge, the Leo T. Cronin Fish Viewing Area, Roy’s Pool near the San Geronimo Golf Course (course now closed), adjacent to the campground at Samuel P. Taylor State Park, and at Devil’s Gulch (a tributary) on the north side of Sir Francis Drake in Samuel P. Taylor.

The best bet is to park at the Leo T. Cronin Fish Viewing Area, or, if full, at nearby Samuel P. Taylor State Park. It is peaking as the spawning season winds down.

The Inkwells are located on the north side of Sir Francis Drake Boulevard, about a half-mile west of the Lagunitas Store and just east of Samuel P. Taylor State Park. This is where 40 salmon were sighted in about two hours Friday.

Most viewers then walk to the nearby Leo T. Cronin Viewing Area, across the road. “From Leo Cronin, we saw bright red males, fish courtship and females digging nests,” Angel said.

One of the best options is to instead go to nearby Devil’s Gulch. As you drive west on Sir Francis Drake, just past the formal park entrance, park on the dirt pullout on the left, directly across the road from a gated service road. Cross the road and hike a short distance to the overlook and bridge (on the right) at the creek, where you can look down this week and might see fish sex.

Tom Stienstra is The San Francisco Chronicle’s outdoors writer. Email: tstienstra@sfchronicle.com Twitter: @StienstraTom