Research indicates that rising water temperatures slow salmon growth and show signs of liver dysfunction. Both freshwater and saltwater environments exhibit similar responses, highlighting the importance of managing high temperatures throughout the salmon farming process.
On October 15, the Korea Institute of Ocean Science and Technology (KIOST) reported that a research team led by Dr. Kang Hye-min analyzed the effects of rising temperatures on the growth and liver function of juvenile Atlantic salmon.
The team focused on the salmon's transition between freshwater and saltwater. While previous studies primarily concentrated on one environment, this research compared high-temperature stress responses across different salinity conditions.
The experiment involved salmon in the 'smolt' stage, which undergo physiological changes to move from freshwater to saltwater. The researchers placed the salmon in separate tanks of freshwater and saltwater, then gradually increased the temperature in some tanks by 1 degree per hour, starting from the optimal growth temperature of 14 degrees.
After reaching the target temperature, the salmon were observed for five days. Only the salmon in the 14-degree tank showed weight gain. No weight increase was observed at temperatures above 18 degrees, and at 26 degrees, some salmon in both freshwater and saltwater died.
Blood tests also revealed abnormalities associated with high temperatures. Notably, in the 26-degree freshwater tank, the level of ALT, an enzyme used to assess liver damage, significantly increased. Additionally, protein levels in the blood decreased in both environments.
Changes in gene activity related to high-temperature responses were also noted. Genes associated with heat shock proteins (HSP90), which help repair damaged proteins, and enzymes that protect cells from oxidative stress (GPX) showed altered activity in response to rising temperatures in both environments. This indicates that the salmon's bodies reacted defensively to prevent cellular damage due to perceived stress from elevated temperatures.
The research team explained that these results demonstrate that high temperatures can impact salmon growth and physiological functions, regardless of salinity conditions.
Along the Korean coast, prolonged high-temperature phenomena during summer are becoming more common. According to data released by the National Data Center in March, the number of days with high-temperature advisories nationwide increased from 47 days in 2021 to 71 days in 2024, and 85 days last year. Since salmon stop gaining weight at just 4 degrees above the optimal temperature of 18 degrees, concerns are growing that prolonged high temperatures during summer could lead to decreased growth and increased mortality in farming processes.
Dr. Kang Hye-min stated, "As high temperatures recur every summer, managing water temperatures in aquaculture has become increasingly important. The findings from this study can serve as indicators for monitoring high-temperature stress throughout the entire process of farming salmon, from freshwater to saltwater."
* This article has been translated by AI.
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