No salmon up the creek (Point Reyes Light, 03.05.2009)

Only a handful of fish were found in the Lagunitas Creek watershed this winter season—making it the lowest coho count on the record for Olema Creek.

Coho salmon—listed as endangered since 2005—return to spawn in creeks between November and late February, known as the spawner year. This is the fourth year of observable decline in the endangered coho salmon population in Olema Creek—a decline some believe has resulted from unfavorable ocean conditions and late winter storms.

“We know that quite a few fish made it out to the ocean. The return rates were just really low,” said Michael Reichmuth, a fishery biologist with the National Park Service, who just conducted his third coho salmon survey this winter.

“This year, what we normally see in the early summer is what we’re seeing in December and January,” Reichmuth added. “We ran out of water, which caused passage issues. The woody debris jammed, and fish couldn’t get around that during low flow.”

The total coho count for the season was two redds (or nests) and three fish observed on Redwood Creek, and two live coho with only one coho redd observed on Olema Creek. Last year’s counts were just as gloomy.

Between eighty and 180 return to Olema Creek from the ocean every year. During the 2004-05 spawner year, Olema Creek had at least 184 fish—but the numbers have decreased ever since. However, there is not enough data to statistically show a declining trend outside of the regular fluctuations in the population.

Survey cycle

After adult females lay their reddish-orange eggs in gravel at the bottom of the creek, they die. During spawner surveys this winter, Reichmuth and his volunteers counted live adults, carcasses and redds.

When the salmon hatch, they find their way six inches down into the gravel and emerge a few weeks or months later. This summer, Reichmuth will conduct snorkel surveys to count those fish that were spawned this winter. “Based on what we see in the summer, we can infer what happened in the winter,” he said. It will help him determine how successful the spawning was. After they emerge from the gravel, those young salmon will spend one year in freshwater creeks. Then in the spring, these 4-inch-long juvenile salmon—now called smolts—to out into the ocean.

Beginning mid-March, Reichmuth will use traps to catch smolts as they embark on their migration out to sea—it tells his how successful the spawning was during the 2007-08 spawner year. And it gives him an idea of how many fish he’ll be expecting to return in a year and a half—or spawner year 2010-11.

According to the 2007 trap numbers, plenty of smolts were seen leaving the creek system. “We know that a good number of smolts left and went into the ocean,” Reichmuth said. They grow in the ocean for a year and a half before coming back to the creeks to spawn. The juvenile fish that left in 2007 are the ones that should have returned this winter to spawn.

Coming back

Even though a good number of smolts swam out in 2007, they were greeted by poor ocean conditions. Upwelling in the ocean brings up nutrients and increases productivity. Instead, those fish faced reduced currents and a lack of upwelling. And they couldn’t find food when they first went into the ocean.

If they did survive for a year and a half in the ocean, there are still several obstacles to survival before returning to spawn in the Lagunitas Creek watershed this winter.

Before these recent storms, seafaring coho spawn had to deal with drought conditions before they could return to freshwater streams. “They might have come towards the creek too early,” Reichmuth added. “Well, normal timing for them, but early relative to the late storms we had.” The lack of rain forced low flows, and the fish simply couldn’t make it into the creek.

If there were high numbers of fish holding out near the coast waiting to come into the creek, predators, like seals and sea lions, could pick them up before they can swim in. “I’ve seen otters wait right at the mouth of Olema Creek,” Reichmuth said.

Likely, it was a combination of poor ocean conditions and the late storms. “A lot of salmon went out, but not a whole lot of spawners came back, and on top of that, without enough rain, the ones that do come back can’t even get into the creek,” Reichmuth said.

But 2008 had favorable ocean conditions—lots of upwelling and good currents. Reichmuth expects better returns in 2009-10, especially if the rains come at the right period of time.

“We are now past the typical window for coho spawning, and I don’t expect to find any new Coho spawning activity even after this last set of storms,” Reichmuth wrote in an email to his volunteers.

The late rains this winter could still help. Reichmuth will conduct another spawner survey next week, when the water clears up after this week’s storms, and there will be better visibility. Surveyors in Scott Creek near Santa Cruz, who have coated fish with tags that act like FasTrak on cars, have picked up signals that coho have gotten into creeks south of Lagunitas Creek watershed during the recent larger storms.

“There’s still enough water that if the fish want to come up, they will,” Reichmuth said. “Right now, the streams are pretty much wide open. I’d like to be surprised.”

For volunteer opportunities within the Point Reyes National Seashore, visit http://www.nps.gov/pore/supportyourpark/volunteer.htm

~ by Janet Fang on March 6, 2009.

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