2021

Karjalainen, Juha; Tuloisela, Markus; Nyholm, Kristiina; Marjomäki, Timo J.

Depending on their reproductive strategy, different fish species either aggregate or disperse eggs and larvae in their reproductive habitat. Because yolk-sac larvae of vendace (Coregonus albula) disperse widely across the littoral and pelagic zones of boreal lakes, it is unclear where the exact spawning and egg incubation locations are. Vendace egg and larvae densities were studied in Lake Southern Konnevesi to clarify its spawning strategy. In autumn 2019, 1–2 weeks prior to spawning, 500 egg samplers were installed in five depth zones in 20 sampling plots. Fertilized eggs were found in 18 plots. The mean density of eggs was 74 eggs m–2 and the mean fertilization rate 85%. During spawning, vendace dispersed their offspring throughout the lake. The sampling-plot-specific egg density in autumn 2019 did not correlate with larval density in the spring next year. The reproduction strategy of vendace reduces the effects of high spatial and temporal fluctuation in their reproduction and nursery habitats.