How Did the Late 1980s Climate Regime Shift Affect Temperature-Sensitive Fish Population Dynamics: Case Study of Vendace (Coregonus albula) in a Large North-Temperate Lake

Abstract

The population dynamics of fish in northern lakes is strongly influenced by climatic factors. In this study, we investigated whether there is a link between the late 1980s climate regime shift in Europe and the collapse of vendace (Coregonus albula) population at the same time in Lake Peipsi. Until the end of the 1980s, vendace was very abundant in the lake, but then its catches sharply declined. This decline inspired investigations into the extreme weather events preceding the vendace collapse using data on daily water temperatures and ice phenology together with commercial fishery statistics since 1931 and test catch data since 1986. We identified using advanced statistical methods that the hot summer of 1988, which was accompanied by a severe cyanobacterial bloom and extensive fish kill, and the subsequent non-permanent ice cover and early ice-offs in 1989 and 1990 in Lake Peipsi were the main reasons for the disappearance of vendace from catches in 1991. Moreover, a negative correlation appeared between catches of the predatory pikeperch (Sander lucioperca) and vendace. Predation pressure as well as fish habitat degradation caused by lake eutrophication may contribute to the instability of the vendace population too. Our study showed that extreme weather events such as heat waves in summer and non-permanent ice-cover in winter in consecutive years may have long-lasting harmful effects on the population abundance of cool-water fish species such as vendace whose eggs usually develop under an ice cover in north-temperate lakes.

Using the “mean temperature of the catch” to assess fish community responses to warming in a temperate lake

“…Fish community in a large shallow lake such as Peipsi responds not so much to a long-term slow rise in yearly average water temperature as to short-term extreme weather events, e.g., heat waves, accompanied by cyanobacterial blooms, anoxia during night, and fish kills (Kangur et al 2013). An abrupt increase in water temperature recorded at the end of 1980s was linked to the collapse of vendace population: the hot summer of 1988, which was accompanied by a severe cyanobacterial bloom and extensive fish kill, and the subsequent non-permanent ice cover and early ice-offs in 1989 and 1990 in Lake Peipsi were the main reasons for the disappearance of vendace from catches in 1991 (Kangur et al 2020).…”

“…Shifts in the abundance of exploited species are expected to affect their availability to fisheries, as already observed in freshwater fisheries in Europe (see, e.g., Jeppesen et al 2012;Sandström et al 2014). In Lake Peipsi, the effects of high water temperatures (e.g., heat waves) in summer and extreme ice conditions on the abundance of some targeted species, e.g., lake (dwarf) smelt (Osmerus eperlanus) ) and vendace (Coregonus albula) (Kangur et al 2020), have been identified. However, a climate change signature for the entire fisheries of Lake Peipsi has so far not been detected.…”

“…In the late 1930s, pike-perch became another important commercial fish in the lake. From the 1950s to 1970s, the catches of pike-perch decreased, but, in the late 1980s, the catches of pike-perch increased explosively (Kangur et al 2020). At that time, vendace was of great importance for commercial fishing in Lake Peipsi.…”

“…The main shift in the Peipsi fish community from cool-water species such as vendace, burbot, Peipsi whitefish, and lake (dwarf) smelt, whose abundance has declined markedly, toward more warm-water species like pike-perch and bream took place at the turn of the 1980/1990 decade (Kangur et al 2007a, b, c;, which coincided with the shift in the regional climate regime (Jaagus et al 2017). In the late 1980s, a sharp decline in cool-water vendace population coincided with a major increase of warm-water pike-perch (Figure Kangur et al 2020).…”

“…Nutrient (surface water 0-1 m), chlorophyll a (integral sample), and water transparency values are presented as arithmetic means with minima and maxima (in brackets). All estimates correspond to the open water period (May-October) of 2010-2019 (afterKangur et al 2020)…”