Lifting the Vendace, Coregonus albula, on the Life Table: Survival, Growth and Reproduction in Different Life-Stages during Very High and Low Abundance Regimes

Abstract

We analyzed the variability in vendace population parameters in the context of a life table. Parameters related to growth, fecundity and survival were estimated for post-recruitment (age > 1 growing season) life stages of Lake Southern Konnevesi vendace in both very high and low population abundance regimes. Pre-recruitment survival producing population stability was then determined. We found a very strong compensatory density dependence in growth, fecundity and survival: during low abundance, a lifetime reproductive output of a female was almost 20 times that of the abundant regime. To maintain the low abundance regime, pre-recruitment survival must counterbalance it by decreasing to a very low level. Potential drivers of high variability in pre-recruit survival and potential for depensation, Allee effect, are discussed, as well as the implications of the results on fisheries management and risk of extinction due to anthropogenic stressors such as global warming or extensive predator stocking.

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

“…The temporary change in the sex ratio is expected to be most pronounced during the period of a steep decline in the spawning stock, when recruitment failure is initially triggered by another agent (e.g., weather, Marjomäki et al 2004) and there are still spawners from the last abundant year‐class. Once the population enters a more stable phase of low abundance regime, the sex ratio is expected to return to a less extreme level while the low regime is maintained due to some other factors affecting prerecruit mortality (Marjomäki et al 2021b). Therefore, the dynamics of the sex ratio may be one of the factors contributing to the very dramatic collapse in recruitment during the transition from the abundant to the sparse regime.…”

The ecology and fishery of the vendace (Coregonus albula) in the Baltic Sea

“…This variation has been observed both as cyclic fluctuations (Marjomäki, Auvinen et al, 2021) and more irregular alternations between strong and weak year‐classes (Axenrot & Degerman, 2016; Sarvala et al, 2020). The postulated drivers of these oscillations include density‐dependent survival of the youngest cohort, competition for food between cohorts, as well as other intraspecific interactions (Hamrin & Persson, 1986; Marjomäki Valkeajärvi et al, 2021). However, evidence also suggests that fishing mortality (Sarvala et al, 2020), environmental factors (Auvinen et al, 2004; Marjomäki et al, 2004), and interspecific interactions (see below for details) can markedly affect the variation in population abundance.…”