The Formosan landlocked salmon. Photo courtesy of the Shei-Pa National Park Headquarters
Taipei, Oct. 26 (CNA) The endangered Formosan landlocked salmon has successfully reestablished itself in the upper reaches of Sijielan Creek in central Taiwan, with a recent survey recording 117 adult fish after an aerial release last year, the Shei-Pa National Park Headquarters said Monday.
The survey found a visible survival rate of nearly 50 percent and documented courtship and pairing behavior, indicating the fish are likely to spawn naturally in the wild as early as November, the headquarters said in a statement.
The fish, now nearly 2 years old, have matured into healthy adults, with males and females displaying distinct secondary sexual characteristics.
The headquarters described Sijielan Creek as the final piece of the puzzle in restoring the species across its historic habitat in the Dajia River basin.
The salmon had already been successfully restored in Qijiawan, Hehuan, Nanhu and Luoyewei creeks, while several earlier reintroduction campaigns in Sijielan Creek failed because of habitat degradation.
According to Atayal traditional knowledge, Sijielan Creek once supported an abundant wild population of the salmon, which later disappeared because of environmental changes and human development.
The creek's habitat began to recover about a decade ago when floodwaters destroyed a downstream check dam. Natural erosion of the riverbed then recreated the deep pools and gravel beds the salmon need.
In September 2025, the headquarters used a helicopter for the first time to airlift 240 salmon, then about 10 months old, to the upper reaches of Sijielan Creek for release.
To assess the outcome, a research team set out from Huanshan Village earlier this month, trekking 3.1 kilometers along the Mt. Zhijayang trail before descending into the river valley and wading 5.5 kilometers upstream for an overnight survey.
Snorkeling along a 600-meter section around the release site, the team recorded 117 adult salmon, an observed survival rate of 48.75 percent.
Because fish were also seen beyond both ends of the surveyed section, suggesting some had dispersed farther upstream and downstream, the actual survival rate could exceed 50 percent, the headquarters said.
The headquarters said it would continue to monitor the emergence of juvenile salmon and the population's resilience to flooding, with full annual survey results expected at the end of the year.
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