Vendace (Coregonus albula) Disperse Their Eggs Widely during Spawning

Abstract

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.

Opposing growth trends in juvenile and mature Humpback Whitefish within the upper Tanana River drainage, Alaska, revealed using otolith biochronology

“…For example, reductions in prey abundance have been attributed to growth declines in Lake Whitefish within the Laurentian Great Lakes due to the establishment of invasive dreissenid muscles (Pothoven et al 2001;Nalepa et al 2005;Hoyle et al 2011). However, additional studies have reported negative correlations between cohort strength and growth, suggesting that densitydependent competition for limited food resources acts as a growth-regulating mechanism for coregonids (Freeberg et al 1990;Karjalainen 1992;Kratzer et al 2007a), a result further supported by studies in experimental lakes (Healy 1980;Mills et al 1995). Yet still, environmental conditions are believed to influence spawning and hatching success (Freeberg et al 1990;Brown et al 1993;Kratzer et al 2007b), while water temperature, specifically, has been shown to influence growth in laboratory studies (Edsall 1999;Szczepkowski et al 2006).…”

Males die young, which may cause an Allee effect during a population collapse of the Vendace Coregonus albula

“…However, more understanding of the effect of sex ratio on reproduction rate can be obtained from laboratory experiments (Rowe et al 2004). Recently, we have also succeeded in sampling spawned Vendace eggs from the spawning sites (Karjalainen et al 2021), which enables the estimation of the fertilization rate in situ and the comparison of fertilization rates under different spawner densities and sex ratios in different years.…”

“…No sexual dimorphism, such as differences in size at age (e.g., data by Järvi 1919Järvi , 1920Järvi , 1942aViljanen 1986) or age at maturity or any secondary sexual characteristics, has been detected in Vendace. Despite being a pelagic schooling species for most of the year, Vendace spawn in pairs (Karjalainen and Marjomäki 2018) in the littoral-sublittoral zone from a depth of a few meters to more than 10 m (Heikkilä et al 2006;Karjalainen et al 2021). Spawning takes place in late autumn in the dark.…”

Effects of warming winter embryo incubation temperatures on larval cisco (Coregonus artedi) survival, growth, and critical thermal maximum

“…Most coregonines spawn nearshore in late-autumn, embryos incubate under ice, and hatch in spring near ice-out, when rising spring water temperatures trigger hatching (Karjalainen et al, 2021(Karjalainen et al, , 2019(Karjalainen et al, , 2015Stockwell et al, 2009). Increases in air temperature and water temperatures of seasonally ice-covered lakes are projected to be greatest during the winter and spring, respectively, in response to climate change (Christensen et al, 2007;Ozersky et al, 2021;Schindler et al, 1990;Winslow et al, 2017).…”