Oregon, United States – Conservation teams have released Pacific lamprey back into the wild after months of care in a coordinated restoration effort above Detroit Dam.

Zoo staff, along with Tribal and agency partners, released 23 of the ancient fish into the North Santiam River as part of a tribal-led program aimed at restoring the species in the region.

The group had spent nine months at the Oregon Zoo after arriving in June from Willamette Falls. This marked the first time a group from that population had been held in human care.

Other lamprey collected at Willamette Falls were released directly at the site without being placed in human care, allowing researchers to compare different approaches to release and overwintering.

Conservation officials say analyzing both methods will help determine the most effective strategy for rebuilding lamprey populations.

While at the zoo, the lamprey underwent health monitoring, including lab testing and CT scans, with scientists studying their development prior to release.

Researchers will later use DNA analysis to compare the reproductive success of the zoo-held lamprey with those released earlier.

The Pacific lamprey is a jawless, scale-less fish that has survived ice ages and mass extinction events, but its numbers have declined over the past 75 years due to habitat loss, climate change, passage barriers, and food scarcity.

Another group of lamprey from Willamette Falls is expected at the Oregon Zoo in the coming months for a similar nine-month care and release cycle.

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