The impact of climate variability on recruitment, life history, and physiology of sympatric pairs of ciscoes (Teleostei: Coregonus spp.) in lakes

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Recently, it has been speculated that global warming trends may favor year-class strengths of spring-spawning in opposition to autumn-spawning fish species. The mechanisms behind were assumed to be a differential timing of the hatching of fish and the spring peak of the zooplankton as food for the small fish, and a variable recruitment due to temperature-sensitive adaptations of the life cycle. Here, we compare the timing of hatch and early recruitment of a sympatric pair species of ciscoes in a deep lake whereby one species spawns in autumn, and the other in spring. In this postglacial lake, speciation and divergence have occurred during the last 10,000 years. The ecological, behavioural and physiological differences between both species (except for the spawning time) are assumed to be low. By following the growth, feeding, distribution and physiological performance of the early life stages of both species, we want to test whether the spring-spawning species is indeed better adapted to the anticipated earlier ice break and higher spring water temperatures due to global warming. Furthermore, the predation risk against piscivorous fish is estimated for both species by inspecting the stomach content of littoral predatory fish. In the future, the physiological adaptation of both species and potential hybrids to cold and warm temperatures shall be analysed in addition.