A new study links widespread deficiency of vitamin B1, or thiamine, among California Chinook salmon to their deaths. This adds yet another challenge for this iconic species whose population is already imperiled by climate change, habitat loss and overfishing. … Researchers began to suspect an anchovy-heavy diet was to blame when they examined the guts of ocean-caught Chinook salmon from 2020-22. They found anchovies almost exclusively, suggesting the thiamine deficiency in salmon likely stems from eating too many anchovies. … Treating every spawning salmon with thiamine is logistically impossible, [NOAA scientist Nate] Mantua said, but we can support them in other ways, like removing dams and reducing fishing pressure on other important forage species including herring and squid.