Temperature‐related nocturnal vertical segregation of coexisting coregonids

Abstract

Mehner T, Busch S, Helland IP, Emmrich M, Freyhof J. Temperature‐related nocturnal vertical segregation of coexisting coregonids. Ecology of Freshwater Fish 2010: 19: 408–419. © 2010 John Wiley & Sons A/S Abstract – Habitat choice of fish may be influenced by many different ecological factors, e.g., predation risk, feeding opportunity, or temperature and oxygen availability. However, because most of the fish prey and their predators rely on vision for feeding, the predator avoidance and feeding opportunity hypotheses may fail to predict distribution of fish at complete darkness. Here, we accumulated patterns of nocturnal vertical distribution of two coexisting coregonid populations in Lake Stechlin from 13 samplings over 4 years, conducted by hydroacoustics and simultaneous midwater trawling. We calculated population depths, dispersion, illumination strengths and vertical temperature gradients for all sampling dates. Illumination strengths at fish population depths were far below the critical levels for feeding by vision, suggesting that predator avoidance or feeding opportunity did not trigger the depth distribution at night. In contrast, nocturnal population depths and dispersion of vendace Coregonus albula were significantly associated with the seasonally changing vertical temperature gradient in Lake Stechlin, whereas night‐time distribution of the coexisting Fontane cisco Coregonus fontanae was almost unaffected by temperature. Vendace occurred just below the thermocline in isothermal water layers of about 6.5–9 °C during stratification of Lake Stechlin, whereas Fontane cisco preferred 4–6 °C cold layers. These experienced temperatures roughly correspond to species‐specific optimum metabolic temperatures determined in earlier experiments. We assume, therefore, that the temperature‐related vertical segregation during non‐feeding hours at darkness is linked with metabolic benefits, thus suggesting that bioenergetics efficiency contributes to ultimate causes of diel vertical migrations at least in vendace.

Adaptive Phenotypic Diversification along a Temperature-Depth Gradient

“…This model outcome matches the experimentally determined species-specific thermal preferences and corresponding temperatures of lowest swimming costs (4.2Њ and 9.0ЊC; Ohlberger et al 2008bOhlberger et al , 2008c and is in good accordance with the experienced water temperatures of the coregonids in Lake Stechlin (4.0Њ-6.0Њ and 6.5Њ-9.0ЊC; Mehner et al 2010a). These comparisons show that the two populations that evolve in our model represent well the natural populations in terms of their distributions and trait values.…”

“…The species differ in their average population depths within the pelagic zone, with C. fontanae being found deeper in the water column than C. albula throughout the year. This difference in depth distribution is associated with a difference in mean experienced water temperature (Helland et al 2007;Mehner et al 2010a).…”

Three‐dimensional internal spatial structure of young‐of‐the‐year pelagic freshwater fish provides evidence for the identification of fish school species

“…2). Under the thermocline, the deeper layers are inhabited by salmonids (Mehner et al 2010); above it, in the surface layers, juveniles of Cyprinidae (Perca fluviatilis) and Percidae (Rutilus rutilus) school during the day and disperse at sunset to feed (Masson et al 2001;Probst et al 2009). …”

Ecological commonalities among pelagic fishes: comparison of freshwater ciscoes and marine herring and sprat

“…841 An additional ultimate cause of DVM was put forward 842 for the coregonids of Lake Stechlin, where hydroacoustic 843 observations of population depths at night revealed strong 844 seasonal fluctuations, with fish occurring in deeper water in 845 spring and autumn than during the summer months 846 (Mehner et al 2005(Mehner et al , 2007b. There was a significant cor-847 relation between population depths and vertical tempera-848 ture gradients (Mehner et al 2007b;Busch and Mehner 849 2009), suggesting that fish seek layers with metabolically 850 optimum temperatures at night (Mehner et al 2010a …”

“…342 Large-scale synchrony in population abundances of core-343 gonids suggests that there is an important density-inde-344 pendent mechanism influencing recruitment (Marjomäki 345 et al 2004;Bunnell et al 2010), most likely driven by the 346 temperature development during winter and early spring 347 and date of ice break Mehner et 361 Adults of spring-spawning species are pelagic and co-occur 362 locally with vendace where sympatric, but may display 363 vertical segregation from vendace (Mehner et al 2010a).…”