Lake Biwako's Ayu Catch Plummets to Record Low, Threatening Industry and Livelihoods
The January haul of ayu sweetfish from Lake Biwako, Japan's largest lake, was a mere 3% of the average, marking the lowest catch since record-keeping began in 2009. This drastic decline is attributed to poor spawning conditions caused by the scorching heatwave experienced last summer.
The impact of the low catch is far-reaching, affecting not only the ayu industry but also the livelihoods of fishermen who depend on this iconic fish species for their income. Fisheries cooperative associations are struggling to fulfill orders from ayu breeders, and shipments to retailers and restaurants have fallen behind. Some fishermen have been forced to suspend operations due to financial constraints, causing significant hardship and uncertainty.
The scorching heatwave that persisted through September 2023 is believed to be the primary culprit behind the poor spawning conditions. The water temperature in rivers flowing into Lake Biwako reached 24 degrees during the ayu spawning season of September and October, 2 degrees higher than the average. This, coupled with low rainfall and decreased river water volume, resulted in a significant decline in the number of ayu eggs.
Paradoxically, a fishery experiment station observed approximately 20% as many ayu shoals in January 2024 as in an average year. This discrepancy has prompted the Shiga prefectural government to conduct further investigations to understand the factors contributing to the low catch.
The low water level in Lake Biwako, which has persisted since autumn, has also raised concerns. While no direct link between the drought and the poor catches has been established, Governor Taizo Mikazuki acknowledged that fishermen have reported changes in water currents around the "eri" nets due to the low water level, potentially affecting ayu migration patterns.
The Shiga prefectural government is closely monitoring the situation and exploring potential solutions to mitigate the impact of the low catches. These solutions may include financial assistance for affected fishermen, research into alternative fishing methods, and efforts to improve spawning conditions.
The future of the ayu industry in Lake Biwako remains uncertain. However, the resilience and ingenuity of the fishermen, coupled with the support of the government and the community, offer hope for a recovery.