Banri Koda’s research while affiliated with Kindai University and other places

Honmoroko ( Gnathopogon caerulescens ), an endangered species endemic to Lake Biwa, is adversely affected by the desiccation of eggs caused by the water level management and deterioration of spawning habitats (lakeshore vegetation zone). Despite a recent study of foreshore spawning of the species having suggested that some local environmental conditions may be related to foreshore spawning habitats selection by the species, no quantitative studies have examined the conditions that determine the suitability of such habitats. The present survey of Honmoroko eggs around emergent vegetation zones along the foreshore in two study areas indicated that Honmoroko selectively spawn at shallow sites with greater water velocity, utilizing emergent plants, such as Salix spp. . The findings confirmed the importance of protecting the spawning habitats around the Lake Biwa shoreline and have important implications for the controlled management of Lake Biwa water levels with regard to Honmoroko spawning.

With a view towards effective fisheries management, catch features, including catch per unit effort (CPUE; number of fish caught per angler per hour), sex ratio and maturity status of Honmoroko Gnathopogon caerulescens caught by recreational anglers using long dip nets in the Shinyamaji River inlet to Ibanaiko Lagoon, adjacent to Laka Biwa, were examined. Mature individuals caught from April to June 2020 and 2021 were characterized by the CPUE ranging from 10 to 50, and high gonadosomatic index, the sex ratio tending to be more female biased during the periods of higher CPUE. The higher catches achieved by using long dip nets may be related to the spawning behavior of Honmoroko in the inlet to the lagoon, indicating the importance of evaluating the recreational catches for the management of Honmoroko in Lake Biwa.