As cool Autumn air flows along the winding Sacramento River, thousands of sleek and graceful North American green sturgeons swim along the riverbed after spawning upriver last spring. Amongst those making their migratory journey this fall are 25 fish that will play an important role in growing their species’ numbers, albeit with some help from U.S. Army Corps of Engineers planners.
For the past four years, fish biologists with USACE’s Sacramento District Planning Division have spent Mondays and Fridays from September through October on the 300-mile-long river where it passes through Hamilton City, angling in a 20-foot fishing hole favored by the ancient bottom-dwellers.
But they’re not there for sport. They’re there to help recover the species that since 2006 has been listed as threatened under the Endangered Species Act.
On a recent Friday, with sweat beading on his forehead as he firmly gripped a 100-pound fishing line attached to a hefty 6.5-foot sturgeon skimming the water’s surface alongside a boat, USACE senior fisheries biologist Robert Chase took in the moment as the boat and fish slowly moved toward shore where the art of fishing was about to combine with science and environmental stewardship and conservatorship.
“People say I fish for a living, but when you catch five or six of these in a day, it’s real work,” the Vacaville, California native said with a smile. “But in reality, this is just where our work starts.”
Chase’s work is part of USACE’s efforts to catch, tag and monitor green sturgeon behavior in and around their ongoing civil works projects along the Sacramento River as required by the National Marine Fisheries.
“Our hypothesis is that our erosion reduction and flood control projects have caused little to no change in fish behavior in the urbanized portions of the river,” he said, “but we need to study their behavior to prove that true.”
Doing so, Chase said, will enable the Sacramento District to stay on track with construction schedules, better negotiate information for consultations, and provide more references for future mitigation actions.
Prior to USACE’s tagging efforts, little information about green sturgeon activity in the lower portion of the Sacramento River existed, so in addition to helping USACE civil works planners minimize project impacts, it also helps inform the decisions of other federal, state, county, academia, and tribal agencies that are also working to help recover the species.
Sacramento District Deputy Commander Lt. Col. Dianna Lively joined Chase for the tagging expedition to give her a chance to see the organization’s efforts to engineer with nature firsthand.
“Field visits like this are always enjoyable and productive because it gives me a unique opportunity to see our team’s remarkable efforts up close, and in this case, see and actually touch nature as we work to identify what impacts construction along waterways truly have on the species, and be an agent of positive change,” said Lively.
On the muddy riverbank, Chase and contractor Michael Hellmair, a fellow fisheries biologist with Fishbio, Inc., gently turned over one of three sturgeons Lively caught, and within seconds it slipped into an apparent catatonic state before they began tag insertion.
While Hellmair ensured that the fish received enough oxygen, Chase used medical grade surgical tools to take a tiny genetic sample before making a small incision in the underside of the fish and inserting a PIT (Passive Integrated Transponder) and an acoustic tag before closing the cut with dissolvable sutures.
“The most important thing is that they swim away,” Hellmair said quietly.
Once the tagging was complete, they carefully turned the fish upright, and in about 30 seconds it woke from its apparent slumber and swam away. Within two to three months, it will head southward with its group to the brackish waters of the San Francisco Bay. There, the bottom opportunistic predators feast on clams and shrimp before continuing along the West Coast as far south as Baja, Mexico or as far north as Alaska before returning to the Sacramento River every three to five years to spawn.
By the time the tagging process ends in 2028, about 185 telemetric tags will emit signals to stationary receivers deployed along the river from Shasta County to the Golden Gate Bridge. The tags will function for at least 10 years, offering a treasure of useful data for USACE and other West Coast agencies who are looking to better understand green sturgeon behavior.
As the fish repeatedly migrate, data analysis will shed light on their behavior in and around the Sacramento District’s ongoing civil works projects like the Sacramento Bank Stabilization, West Sacramento Levee Improvement, and American River Common Features projects, but their work is already yielding valuable knowledge.
As Chase and Lively removed their mud boots and prepared for the drive back to Sacramento, Chase appeared pleased with the morning’s work and confident that their tagging efforts are making a difference.
“The pre- and post-construction data we’ve captured over the past four years are already helping USACE and our partners better understand potential impacts of erosion reduction and flood control projects,” he said with satisfaction.
It’s said that a bad day fishing beats a good day in the office, but on that morning, the fish-tagging trio proved that a good day fishing (and tagging) beats all.