Particle size distribution shift and diurnal concentration changes of environmental DNA caused by fish spawning behaviour

Abstract

Environmental DNA (eDNA) analysis is a useful method for detecting spawning behaviour by observing elevated eDNA concentrations and/or nuclear/mitochondrial DNA ratios. However, little is known about the characteristics and dynamics of sperm-derived eDNA, which is key to detection. This study focused on changes in eDNA particle size distribution (PSD) and concentrations pre-, post-, and during spawning of Plecoglossus altivelis, to investigate the potential for semi-selective recovery of sperm-derived eDNA and the importance of sampling time for improving detection sensitivity. Firstly, PSD changes between pre- and post-spawning were investigated by comparing concentrations and proportions of eDNA obtained from filters with different pore sizes. Secondly, the diurnal changes in eDNA concentration were monitored at the peak of the spawning season by collecting river water every 1-3 hours. Results showed that eDNA related to sperm-head size increased at post-spawning, and eDNA concentrations had significant diurnal changes with a peak during the spawning time window. These findings suggest that semi-selective recovery of sperm-derived eDNA based on particle size and/or sampling during the spawning time window with increased concentrations can improve the detection sensitivity of eDNA-based spawning surveys. This study provides essential fundamental information for advancing eDNA-based spawning surveys and contributes to their further development.

Identifying spawning timing and locations of jack mackerel in a semi-closed bay using environmental DNA analysis

“…Spawning surveys based on eDNA analysis are still in the developing stage, and their application for fish is currently limited to freshwater areas (ex. lake, Erickson et al, 2016; Vautier et al, 2023; Wu et al, 2023; river, Bracken et al, 2019; Di Muri et al, 2022; Saito et al, 2022; Tsuji and Shibata, 2023). Previous studies investigating fish which spawn in the sea, such as the Japanese jack mackerel ( Trachurus japonicus ) and the Japanese eel ( Anguilla japonica ), have reported significant increases in eDNA concentrations before and after spawning in both species when artificially spawned in laboratory conditions (Takeuchi et al, 2019; Tsuji et al, 2022b).…”