Spawning of Gnathopogon caerulescens on the sandy, gravel, and rocky shores of Lake Biwa, Japan: new findings about potential spawning sites

Abstract

From March to May in 2021, 2022 and 2023, fish eggs attached to sand, rubble, and interstices of stone walls on the shore of Lake Biwa, Yanagasaki, Japan, were collected, and DNA species identification performed for 120 eggs (8 from each of 15 egg populations). A 462-bp region of the mitochondrial cytochrome b gene was sequenced for 85 eggs, all 13 recognized haplotypes being identified as Gnathopogon caerulescens. Spawning behavior of G. caerulescens near the egg collection sites was observed and videorecorded. In former years (before stock numbers decreased), spawning on the lakeshore outside the vegetation zone had been observed, but detailed information on such is now unavailable. This report is a valuable record of potential spawning sites for future conservation efforts.