Casa Grande students fill in fish’s genetic gaps

Casa Grande senior Kerrianne McCarthy’s Tuesday was different than that of any other student in her high school. She spent it wading through boulder-strewn Adobe Creek with biologists and gently handling tiny tissue samples of fingerling steelhead trout.

McCarthy is president of the United Anglers of Casa Grande, a student group that for more than 30 years has played a leading role in restoring fish habitat in Petaluma’s streams.

Now, students are teaming up with scientists from the National Marine Fisheries Service, a branch of the National Oceanic and Atmospheric Administration, to study the genetics of the threatened steelhead. The information they glean could help scientists learn more about how long the fish have been in Petaluma streams and the potential threats their population faces, such as low genetic diversity.

“The exciting part is this has never been done,” said Dan Hubacker, director of United Anglers. “We’ve never had a real understanding at the genetic level: What is the origin of this fish? How closely is it related to steelhead in other watersheds?”

For a long time, students were simply trying to bring awareness to the fact that steelhead existed in Petaluma creeks, Hubacker said. Now that they’ve proven the fish’s presence, they’re getting to help scientists research how to restore the population.

When the Anglers assisted NOAA with a survey of returning adults in three of six Petaluma creeks last spring, they observed just six adult fish, all in Adobe Creek. The discovery indicated that something may be wrong in the watershed, though the science is still out on how many fish it should support overall.

“It clearly isn’t nearly the amount of fish there should be,” Hubacker said. “There’s clearly something going on in Petaluma that the numbers are as low as they are.”

Tuesday morning, two NOAA fisheries biologists and two NOAA volunteers, joined by Hubacker and McCarthy, waded a stretch of Adobe Creek they know is home to steelhead, due in part to surveys the Anglers helped perform. They stalked through the shallow ripples netting the fish using a practice known as electrofishing. One specially trained biologist carried a pole that sent a low-voltage electric current into the water, which momentarily stunned the 2- to 6-inch steelhead and allowed others to capture them with long-handled nets.

McCarthy and one of the biologists, Amanda Morrison, then sat together on overturned buckets and gently took a tiny tissue sample from each fish. Morrison measured the fish and clipped segments of fins and scales using a small knife and scissors; McCarthy recorded her observations and stored each sample in an individual packet. Then, they placed the fish in buckets of aerated water so they could recover before being released back to the creek.

The process is designed to minimize harm to the fish, Hubacker said. It’s specialized work that requires training and permits, which a high school student normally wouldn’t be able to participate in, he added. While McCarthy herself didn’t have the training or permits, she was able to assist the professionals as they worked.

“This is a great learning opportunity,” Hubacker said. “It puts all the restoration work the students are doing in perspective.”

It provided McCarthy a window into a work world she’s interested in joining one day. As they worked together, McCarthy asked Morrison about her biologist job.

“It’s a really cool experience,” McCarthy said, hauling a bucket upstream in camouflage waders. “I know a lot of people don’t get to do this. When the opportunity arises, I try to jump on it.”

The samples will be sent to NOAA’s Southwest Fisheries Science Center Santa Cruz, where scientists will use them to compare the genetics of steelhead from Petaluma’s watershed with that of steelhead from other watersheds along California’s central coast.

“We’re worried that the fish might be the progeny of just a few adults,” Morrison said. That would mean they have little genetic diversity, making them less resilient to disease and change. Scientists already have this genetic information for many of the streams along the central coast, NOAA Fisheries Biologist Bill Coey said. “(Adobe) and Sonoma creeks are a bit of a hole.”

Filling those gaps will help inform plans of how to best manage the watershed to help the fish, Hubacker said. “Knowing the genetics, we’ll be able to make a really solid decision on what needs to be done,” he said.

Tuesday was part of a narrow time window the group had to do the work, when temperatures in the creek were right and the agency still could obtain the permits. Also, once winter rains come, many young fish head out to sea.

For that reason, they wanted to collect as many samples as possible. In total, they got about 100.

“Because our resources are fairly limited, when we get out we want to make the most of it,” Morrison said. “Here, it’s really nice because we have the Anglers, who are so experienced with the watershed.”

Staff Writer Jamie Hansen blogs about education at extracredit.blogs.pressdemocrat.com. You can reach her at 521-5205 or jamie.hansen@pressdemocrat.com. On Twitter @jamiehansen.