It begins, as such matters often do, with the coquettish wiggle of a tail.

With a like-minded mate, that wiggle becomes a spirited, frenzied flapping, and a brief but intense union on a bed of loose gravel into which will be committed the seed of the next generation.

Give the event sufficient vigor – two salmon can indeed make quite a ruckus – and even the neighbors may notice.

“Yesterday was thrilling,” said Robert Tange, who brought out a video camera to document the leaps and splashes of spawning Coho in Manzanita Creek this week. “I was out here for four hours, with my umbrella and my little chair.”

By a count Tange calls conservative, more than 200 of the salmon also known as “silvers” returned to Manzanita Creek on Wednesday. Some paired up early, others were still traveling stag, all driven by the primal urge that replenishes the region’s flagging stock.

Bainbridge fisheries biologist Wayne Daley and city planner Terry Ash confirmed the return of adult Coho to many of the island’s seven fish-bearing streams.

Significant numbers were seen in Boundy Farm pond, part of the stream system feeding Fletcher Bay.

While not yet officially endangered – that dubious distinction goes to the Chinook – the Coho salmon is a candidate for protection, its fortunes waxing with the vagaries of the weather and the encroachment of development.

This week’s robust migration was dramatic largely thanks to creeks swollen by heavy rains, which offset what Daley described as several years of “drought cycle” that hampered past runs.

The results were perhaps most marked in Manzanita Creek, which crosses a number of Miller Road-area properties en route to the estuary and bay.

Three years ago, Tange said, three pairs of Coho ended their journey home from the sea with courtship in the stream next to his home. Two years ago, there were none; last year, just a single pair.

But already this week, six pairs have settled in to complete the cycle of life.

Many more have moved further upstream, thanks to a series of stream “weirs” installed by volunteers several years ago. The small, dam-like constructions moderate the flow of water, allowing salmon to traverse a culvert beneath Miller Road and reach the spawning areas beyond.

“There’s a lot of great habitat up there,” Daley said, on properties that have been preserved from further development by conservation easements.

Efforts to maintain local streams vary from one property to the next. For his part, Tange has spent more than a decade restoring the banks and spawning areas on the 335 feet of Manzanita Creek that wind through his yard.Thursday, the stream banks were rich with green buttercups and ferns, and precipitation still glittered in the filigree of cedars overhead.

Water cascading over a series of weirs washed out most conversation; where the water pooled, occasional raindrops plinked out unheard tunes on the glassy surface.

Every few minutes, a salmon measuring 20 inches or more would burst from the froth – its pink belly bared to the world above – flopping up and over a barrier and into the next pool, there to fin restlessly around the copper bottom.

“They play,” Tange said. “They’ll fall down the waterfall, go back up, fall down.”

Where the pools were shallow, frisky pairs could be seen in mid-union, the females kicking up the gravel for the deposit of eggs. As has been observed in other spheres, suitors will compete for the honor of fertilization, in a ritual that repeats itself over several days.

The fry that hatch will stay in the stream for some 18 months, heading to sea in the spring of 2003 and, assuming they elude predators and fishermen, returning in fall the following year.

Ensuring that this cycle repeats itself in the future, Daley said, requires the protection of stream banks, and limits on the impervious surfaces that come with construction – including lawns as well as driveways – that prevent the absorption of stormwater needed to sustain streams through drier months.

Tange hopes residents will curb their use of pesticides that pollute waterways, kill insects and throw the ecosystem further out of balance.

With the poor runs of the past few seasons, Tange said it will probably be several years before the Coho’s return to Manzanita Creek is as dramatic.

Until then, he’s got more restoration planned, and hopes enlist neighbors and others in the effort.

“There’s a lot of work,” he said. “This project isn’t even close to done.”