The ayu sweetfish, a prized species from Lake Biwako in Japan, has experienced a significant decrease in catch during the fishing season, with the January haul being the smallest since record-keeping began in 2009. This decline has been particularly disheartening for local fishermen, such as those from the Shigacho fisheries cooperative association, who have been part of the industry for decades and have never encountered such low numbers.
The traditional method of catching ayu fry, known as "hiuo" or ice fish, involves a network of netting called "eri" set up in the water during the winter and early spring months. However, despite efforts to maintain these nets, the catch per net has dropped drastically, with an average of only 4.3 kilograms per net in January, a stark difference from the usual average of 149 kg per net over the past decade. The situation has been exacerbated by environmental factors such as last year's prolonged heatwave, which led to higher water temperatures in the rivers flowing into Lake Biwako and affected the spawning conditions for the ayu.
While the exact reasons for the plummeting ayu catch are still under investigation by the prefectural government, concerns have been raised about the impact on the local ecosystem and economy. The low water levels in Lake Biwako have also created challenges for fishermen, as changing water currents around the nets have deterred the fish from their usual routes. The shortage of ayu has not only affected the fishermen but has also disrupted the supply chain, with orders from ayu breeders going unfulfilled and delays in shipments to retailers and restaurants. The prefectural government is closely monitoring the situation and working to understand the causes behind the declining catch to prevent further implications on the industry and community.