In Mutsu Bay in Aomori Prefecture, experienced scallop fisherman Hideto Takada, with over 50 years of expertise, has encountered a new and alarming phenomenon linked to rising seawater temperatures. Last year's record hot temperatures resulted in significant losses, with 30 percent of Takada's scallop fry under a year old succumbing to the adverse conditions. This year, the situation remains dire, with approximately 20 percent of the scallop fry suffering from the impact of elevated water temperatures, a trend previously unseen in the region.
The escalating seawater temperatures in Mutsu Bay are jeopardizing not only the scallop farming industry but also the existence of indigenous fish species in the area. The Aomori Prefectural Industrial Technology Research Center's Fisheries Institute reports that when water temperatures exceed 23 degrees Celsius, the growth of scallop fry slows down significantly, putting them at risk of emaciation and death if temperatures surpass 26 degrees Celsius. During the summer, water temperatures in Mutsu Bay exceeded the critical threshold, leading to prolonged periods of detrimental conditions for the marine life, with temperatures hitting a maximum of 25.3 degrees, significantly higher than the average.
Efforts to mitigate the impact of rising temperatures on scallop fry, such as relocating cultivation baskets to cooler waters, have proved inadequate in offsetting the adverse effects. The Aomori city fisheries cooperative association saw its scallop fry mortality rate soar to 90 percent last year, emphasizing the urgency for effective countermeasures. Fishermen are facing significant economic challenges, with reduced incomes and diminished shipments due to the escalating crisis. Furthermore, the ripple effects of rising seawater temperatures are not confined to Aomori Prefecture, as other regions like Miyagi Prefecture are witnessing declines in marine product catches, prompting the exploration of alternative options such as pearl culturing tests to adapt to changing environmental conditions.