A collaborative study involving Kindai University, Shiga Prefectural University, and the Shiga Prefectural Fisheries Experiment Station has demonstrated that eel fry released into Lake Biwa exhibit significantly better growth compared to those raised in fish farms. This outcome is attributed to the lack of competing wild eels in Lake Biwa, which provides a favorable environment for the released eels to thrive. Eel longevity and the absence of natural competitors in the lake allow these fry to grow larger and healthier.

Historically, Lake Biwa has been a habitat for eels, although their population has greatly diminished over the years. The release of fry into the lake has been an ongoing initiative, with eel being a sought-after delicacy known for its sizable and meaty composition. It is commonly served in upscale restaurants in Kyoto and Tokyo, highlighting its culinary significance. However, the catch volume has dropped from 53 tons in 1957 to only 2-3 tons annually in recent years, indicating a troubling trend in natural eel populations.

The decline in eel numbers correlates to the construction of the Tenkeise Dam in the 1960s, which has obstructed the natural migration of eels from the sea up the Yodo River. This blocking of upstream migration has contributed to the challenges facing eel populations, making the research on their growth in Lake Biwa particularly critical for future conservation efforts and sustainable culinary practices in Japan. The findings could influence fishery management and conservation policies moving forward, encouraging similar initiatives in other areas.