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California Salmon Face 'Ghostly' Demise Amidst Extreme Climate and Altered Rivers

From Hankyoreh · (10m ago) Korean Critical tone

Translated from Korean, summarized and contextualized by DistantNews.

TLDR

  • Extreme climate conditions, including severe droughts and floods, are causing mass die-offs of young salmon migrating in California.
  • Decades of civil engineering have accelerated river flows, creating an "ecological trap" that exacerbates the survival threat for juvenile salmon.
  • Researchers are calling for climate-resilient restoration efforts, including reconnecting wetlands and floodplains, to protect diverse salmon populations.

A stark new study reveals the devastating impact of California's extreme climate on its iconic salmon populations. The research highlights how a combination of prolonged droughts and intense floods is leading to the mass death of young salmon as they navigate the perilous journey from inland hatcheries to the Pacific Ocean. This ecological crisis is not solely due to climate change; decades of civil engineering have drastically altered river systems, increasing water flow speeds and creating what scientists are calling an "ecological trap" that ensnares and kills vulnerable juvenile fish.

The study, published in 'Global Change Biology,' tracked nine generations of Chinook salmon in California's Central Valley. Researchers analyzed the fish's ear bones and eye lenses to reconstruct their migration paths and survival rates. They found that 'early migrating' juvenile salmon, those smaller than 47mm, faced significantly higher mortality rates. While they constituted 80% of the young salmon entering the Sacramento-San Joaquin Delta, their numbers dwindled to just 26% by the time they exited, and a mere 15% returned as adults to spawn. This dramatic decline underscores the severity of the threats they face.

Extreme climate conditions have left young salmon with no choice.

— Rachel JohnsonCo-author of the study and researcher at the US National Oceanic and Atmospheric Administration (NOAA) Fisheries, expressing concern about the future.

The simplification of river systems due to development has eliminated crucial habitats like freshwater floodplains and wetlands, which previously acted as buffers against extreme weather. During a major flood in 2017, many young salmon were swept directly out to sea instead of finding refuge in these vital nursery grounds. The researchers aptly describe these lost fish as "ghosts in the river," disappearing without a trace. This situation demands urgent attention and a shift towards 'climate-ready' restoration strategies that protect diverse salmon populations and restore natural floodplains and wetlands to provide essential refuge in an increasingly unpredictable climate.

The UN climate change scenarios predict that these harsh conditions will occur more frequently in the future.

— Rachel JohnsonCo-author of the study and researcher at the US National Oceanic and Atmospheric Administration (NOAA) Fisheries, highlighting the worsening climate trend.
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Originally published by Hankyoreh in Korean. Translated, summarized, and contextualized by our editorial team with added local perspective. Read our editorial standards.

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