Influence of warming temperatures on coregonine embryogenesis within and among species

ABSTRACT The greatest response of lakes to climate change has been the increase in water temperatures on a global scale. The responses of many lake fishes to warming water temperatures are projected to be inadequate to counter the speed and magnitude of climate change, leaving some species vulnerable to decline and extinction. We experimentally evaluated the responses of embryos from a group of cold, stenothermic fishes (Salmonidae Coregoninae) – within conspecifics across lake systems, between congeners within the same lake system, and among congeners across lake systems – to a thermal gradient using an incubation method that enabled global comparisons. Study groups included cisco (Coregonus artedi) from lakes Superior and Ontario (USA), and vendace (C. albula) and European whitefish (C. lavaretus) from Lake Southern Konnevesi (Finland). All species spawn in the fall and their embryos incubate over winter before hatching in spring. Embryos were incubated at water temperatures of 2.0, 4.5, 7.0, and 9.0°C, and the responses to the incubation temperatures were quantified for life-history (i.e., embryo survival and incubation period) and morphological traits (i.e., length-at-hatch and yolk-sac volume). We found contrasting reaction norms to temperature in embryo survival and similar reaction norms to temperature for incubation period, length-at-hatch, and yolk-sac volume in conspecific and congeneric coregonines. For example, congeneric responses differed in embryonic survival in the same system, suggesting species differences in adaptability to warming winter temperatures. Differential levels of parental effects were found within and among study groups and traits suggesting population biodiversity may provide more flexibility for populations to cope with changing inter-annual environmental conditions. Our results suggest coregonines may have a wide range of embryo responses to changing winter conditions as a result of climate change.