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Öregrund, Sweden

Huss M.,Umea University | Huss M.,Institute of Coastal Research | Van Kooten T.,Umea University | Persson L.,Umea University
Oikos | Year: 2010

Cannibalistic interactions generally depend on the size relationship between cannibals and victims. In many populations, a large enough size variation to allow for cannibalism may not only develop among age-cohorts but also within cohorts. We studied the implications of variation in hatching period length and initial cohort size for the emergence of cannibalism and bimodal size distributions within animal cohorts using a physiologically structured population model. We found that the development of size bimodality was critically dependent on hatching period length, victim density and the presence of a feedback via shared resources. Cannibals only gained enough energy from cannibalism to accelerate in growth when victim density was high relative to cannibal density at the onset of cannibalism. Furthermore, we found that the opportunity for early hatchers to initially feed on an unexploited resource increases the likelihood both for cannibalism to occur and size bimodality to develop. Once cannibals accelerated in growth relative to victims size bimodality, reduced victim numbers and relaxed resource competition resulted. Thus, in addition to that cannibals profited from cannibalism through energy extraction, their potential victims also benefited as the resource recovered due to cannibal thinning. To ensure recruitment success, it can be critical that a few individuals can accelerate in growth and reach a size large enough to escape size-dependent predation and winter starvation. Hence, within-cohort cannibalism may be a potentially important mechanism to explain recruitment variation especially for cannibalistic species in temperate climates with strong seasonality. However, the scope for size bimodality to develop as a result of cannibalism may be limited by low victim densities and size and food-dependent growth rates. © 2010 The Authors. Source

Huss M.,Umea University | Huss M.,Institute of Coastal Research | Nilsson K.A.,Umea University
Journal of Animal Ecology | Year: 2011

1.Recent theoretical insights have shown that predator species may help each other to persist by size-selective foraging on a shared prey. By feeding on a certain prey stage, a predator may induce a compensatory response in another stage of the same prey species, thereby favouring other predators; a phenomenon referred to as emergent facilitation. 2.To test whether emergent facilitation may occur in a natural system, we performed an enclosure experiment where we mimicked fish predation by selectively removing large zooplankton and subsequently following the response of the invertebrate predator Bythotrephes longimanus. 3.Positive responses to harvest were observed in the biomass of juvenile individuals of the dominant zooplankton Holopedium gibberum and in Bythotrephes densities. Hence, by removing large prey, we increased the biomass of small prey, i.e. stage-specific biomass overcompensation was present in the juvenile stage of Holopedium. This favoured Bythotrephes, which preferentially feed on small Holopedium. 4.We argue that the stage-specific overcompensation occurred as a result of increased per capita fecundity of adult Holopedium and as a result of competitive release following harvest. If shown to be common, emergent facilitation may be a major mechanism behind observed predator extinctions and patterns of predator invasions. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society. Source

Van De Wolfshaar K.E.,Wageningen University | HilleRisLambers R.,World Wildlife Fund | Gardmark A.,Institute of Coastal Research
Marine Ecology Progress Series | Year: 2011

In this paper we study the consequences of habitat switching and the corresponding ontogenetic diet shifts between adult and juvenile life stages for harvesting and management of exploited populations using a consumer-resource model with stage-specific mortality. Specifically, we study how differences in stage-specific habitat productivity regulate exploited populations and affect yield. We show that the ratio of adult to juvenile habitat productivity determines whether the population is regulated by processes in the juvenile or adult stage and that population responses to changes in mortality (e.g. fishing) or habitat productivity (e.g. eutrophication or physical destruction) depend critically on the mechanism regulating the population. This result has important consequences for the management of marine fish. For example, in fisheries where the exploited population is regulated by processes in the juvenile stage, management measures aimed at protecting the juvenile habitat may be much more effective than regulating fishing effort on the adults. We find also that intermediate differences in habitat productivity lead to alternative stable states between a population regulated by processes in the juvenile or the adult stage. These alternative stable states may lead to counterintuitive population responses to harvesting. © Inter-Research 2011. Source

Barrett R.D.H.,University of British Columbia | Paccard A.,Institute Of Biologie | Healy T.M.,University of British Columbia | Bergek S.,Institute of Coastal Research | And 3 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2011

Climate change is predicted to lead to increased average temperatures and greater intensity and frequency of high and low temperature extremes, but the evolutionary consequences for biological communities are not well understood. Studies of adaptive evolution of temperature tolerance have typically involved correlative analyses of natural populations or artificial selection experiments in the laboratory. Field experiments are required to provide estimates of the timing and strength of natural selection, enhance understanding of the genetics of adaptation and yield insights into the mechanisms driving evolutionary change. Here, we report the experimental evolution of cold tolerance in natural populations of threespine stickleback fish (Gasterosteus aculeatus). We show that freshwater sticklebacks are able to tolerate lower minimum temperatures than marine sticklebacks and that this difference is heritable. We transplanted marine sticklebacks to freshwater ponds and measured the rate of evolution after three generations in this environment. Cold tolerance evolved at a rate of 0.63 haldanes to a value 2.5°C lower than that of the ancestral population, matching values found in wild freshwater populations. Our results suggest that cold tolerance is under strong selection and that marine sticklebacks carry sufficient genetic variation to adapt to changes in temperature over remarkably short time scales. © 2011 The Royal Society. Source

Von Storch H.,Institute of Coastal Research
Procedia IUTAM | Year: 2013

Storm surges are behind the geophysical risk of short term and abrupt inundating low-lying coastal regions known along most coasts of the world. They are related to meteorological phenomena, mostly wind storms. Storm surges represent a challenge for science and risk management with respect to short term forecasts of specific events but also with long-term changes of the statistics of storm surges due to anthropogenic global climate change, sinking coasts and estuarine water works. Storm surges are expected to become more severe in the coming decades and centuries because of ongoing and expected accelerated mean sea level, and much less so because of more energetic wind storms. © 2013 Published by Elsevier Ltd. Source

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