“Scallop Farms Sway in Prolonged Warm Waters; Research Institute Urges Producers to Take Caution”

The Fisheries Technology Center and the Marine Research Institute are urging scallop producers not to raise or move their culture rafts from deep water at this time. Because seawater temperatures are significantly higher than usual this year, moving scallops while they are in a weakened state could increase mortality and the occurrence of abnormal shellfish. The institute is also advising producers to refrain from attaching seed spat to ropes, cleaning equipment, and conducting mortality checks. Due to the elevated temperatures, the dispersal of juvenile scallops is expected to begin later than usual.

According to the Marine Research Institute, the growth of new and mature scallops slows when water temperatures fall below 20°C, after which they begin consuming energy stored in their digestive glands and adductor muscles. Growth halts at 24–25°C, and mortality risk increases when temperatures exceed 26°C. For juvenile scallops, growth slows above 23°C, and mortality can occur at 24–25°C. During the peak period from late August to mid-September, seawater temperatures reached the 26°C range—well above the typical seasonal average of around 23°C. The average temperature in September was 25°C, marking a record-high level. These conditions are believed to be caused by multiple factors, including rising air temperatures and the inflow of warm currents. The impact on scallops is expected to become clear following the autumn field survey scheduled for November. With temperatures still trending above normal, the institute continues to advise caution among producers.

Meanwhile, the collection of juvenile seed scallops has been relatively favorable in recent years, with improved attachment numbers reported in the western bay area. Attention is now focused on whether these juvenile scallops can withstand the high temperatures and contribute to harvests in the coming year.